Chiginev, Alexander V

Pimanov D.A., Pankratov A.L., Gordeeva A., Chiginev A., Blagodatkin A., Revin L., Razov S.A., Safonova V.Y., Федотов И., Skorokhodov E., Orlova A., Tatarskiy D.A., Gusev N., Trofimov I., Mumlyakov A., et. al.

Abstract Cold-electron bolometers have shown suitability for use in modern fundamental physical experiments. In this study, the fabrication and measurements of the samples with cold-electron bolometers integrated into coplanar antennas are performed. The absorber layer was made using combined aluminum-hafnium technology to improve quality of aluminum oxide layer and decrease electron–phonon coupling. The samples of two types were measured in a dilution cryostat at various temperatures from 20 to 300 mK. The first sample with Ti/Au/Pd antenna shows response in the two frequency bands, at 7–9 GHz with bandwidth of about 20%, and also at 14 GHz with 10% bandwidth. The NEP below 10 aW Hz − 1 is reached at 300 mK for 7.7 GHz signal. The second sample with aluminum made antenna shows response in the frequency range 0.5–3 GHz due to the effect of kinetic inductance of superconducting aluminum.

Revin L.S., Pimanov D.A., Chiginev A.V., Blagodatkin A.V., Zbrozhek V.O., Samartsev A.V., Orlova A.N., Masterov D.V., Parafin A.E., Safonova V.Y., Gordeeva A.V., Pankratov A.L., Kuzmin L.S., Sidorenko A.S., Masi S., et. al.

We consider properties of dichroic antenna arrays on a silicon substrate with integrated cold-electron bolometers to detect radiation at frequencies of 210 and 240 GHz. This frequency range is widely used in cosmic microwave background experiments in space, balloon, and ground-based missions such as BICEP Array, LSPE, LiteBIRD, QUBIC, Simons Observatory, and AliCPT. As a direct radiation detector, we use cold-electron bolometers, which have high sensitivity and a wide operating frequency range, as well as immunity to spurious cosmic rays. Their other advantages are the compact size of the order of a few micrometers and the effect of direct electron cooling, which can improve sensitivity in typical closed-loop cycle 3He cryostats for space applications. We study a novel concept of cold-electron bolometers with two SIN tunnel junctions and one SN contact. The amplitude–frequency characteristics measured with YBCO Josephson Junction oscillators show narrow peaks at 205 GHz for the 210 GHz array and at 225 GHz for the 240 GHz array; the separation of these two frequency bands is clearly visible. The noise equivalent power level at an operating point in the current bias mode is 5 × 10−16 W/√Hz.

Revin L.S., Masterov D.V., Parafin A.E., Pavlov S.A., Pimanov D.A., Chiginev A.V., Blagodatkin A.V., Rakut’ I.V., Skorokhodov E.V., Gordeeva A.V., Pankratov A.L.

The resonant properties of Cold-Electron Bolometers (CEBs) located at a 0.3 K cryostat plate are measured using a 50 μm long high-temperature YBa2Cu3O7−δ (YBCO) Josephson junction oscillator, placed on a 2.7 K plate of the same cryostat. For these purposes, a bunch of YBCO Josephson oscillators with various lengths of dipole antennas and overlapping generation bands has been developed and investigated in 50–500 GHz frequency range. Two setups of Josephson junction placement were compared, and as a result, various narrow-band receiving systems with CEBs have been measured, demonstrating the feasibility of the presented approach.

Glushkov E.I., Chiginev A.V., Kuzmin L.S., Revin L.S.

Modeling of a broadband receiving system based on a meander series of Josephson YBaCuO grain boundary junctions integrated into a log-periodic antenna was carried out. The electromagnetic properties of the system, namely amplitude–frequency characteristic, beam pattern, and fraction of the absorbed power in each Josephson junction were investigated. Based on the obtained results, a numerical simulation of one-dimensional arrays was carried out. The dc characteristics of the detector were calculated, that is, current–voltage characteristic, responsivity, noise, and noise-equivalent power (NEP) for a 250 GHz external signal. The optimal number of junctions to obtain the minimum NEP was found. The use of a series of junctions allows one to increase the responsivity by a factor of 2.5, the NEP value by a factor of 1.5, and the power dynamic range by a factor of 5. For typical YBaCuO Josephson junctions fabricated on a ZrYO bicrystal substrate by magnetron deposition, the following parameters were obtained at a temperature of 77 K: responsivity = 9 kV/W; NEP = 3·10−13 W/Hz(1/2); power dynamic range = 1·106.

Revin L.S., Pimanov D.A., Blagodatkin A.V., Gordeeva A.V., Pankratov A.L., Chiginev A.V., Rakut’ I.V., Zbrozhek V.O., Kuzmin L.S., Masi S., de Bernardis P.

We present the results of the experimental and theoretical study of the resonant properties and noise of a single cell of a receiving system based on cold-electron bolometers (CEB) with a double-folded slot antenna and coplanar lines. The system was designed to receive signals at 220/240 GHz frequencies with a 5% bandwidth. In measurements, we used the samples of the double-folded slot antennas with slot lengths of 162 um and coplanar line lengths from 185 to 360 um. Measurements of the resonance properties of CEB located at 0.3 K cryostat plate were carried out using a generator based on a high-temperature YBCO Josephson junction located inside the same cryostat at 4 K plate. This arrangement made it possible to obtain smooth amplitude-frequency characteristics with a clearly defined peak of a 15–21 GHz bandwidth at different frequencies. Based on these results, 2-D array of double-folded slot antennas with CEBs as 220/240 GHz LSPE channel prototype was calculated.The absorption efficiency of the array has reached 81% and 77% for 220 and 240 GHz channels, respectively.

Revin L.S., Pimanov D.A., Blagodatkin A.V., Gordeeva A.V., Zbrozhek V.O., Masterov D.V., Parafin A.E., Pavlov S.A., Pankratov A.L., Rakut’ I.V., Fil’kin I.A., Chiginev A.V., Kuzmin L.S., Masi S., de Bernardis P.

We present the results of theoretical and experimental studies of the resonant properties of a single cell of a receiving system based on cold-electron bolometers (CEBs) with a double-slot antenna and curved coplanar lines, which is intended for receiving a signal in the range 220–240 GHz with a bandwidth of 5%. The resonant properties of a CEB located on the cryostat plate with a temperature of 0.3 K, are measured using an oscillator based on high-temperature superconductor (HTS) of yttrium barium copper oxide (YBCO), placed inside the same cryostat on a plate with a temperature of 4 K, which allows one to obtain smooth amplitude-frequency characteristics.

Kuzmin L.S., Pimanov D.A., Gordeeva A.V., Chiginev A.V., Masi S., de Bernardis P.

Abstract We are developing multi-chroic double-slot antenna with cold-electron Bolometer (CEB) on-chip filters for the 220/240 GHz interstellar dust monitoring channels of the LSPE–SWIPE experiment. For this goal, we used a narrowband double-slot resonant antenna with CEBs connected by coplanar lines. The simulations show that we have achieved 5% bandwidth for 220 GHz and 5.5% bandwidth for 240 GHz in our numeric modeling for the single cells. A series array of unit cells using double-slot design and coplanar lines with CEBs shows proper frequency selection. Estimations of the noise properties of the CEB arrays in a voltage-biased mode with the SQUID readout show photon-noise limited operation for the optical power load of 6 pW for channel 220 GHz and 20 pW for channel 240 GHz.

Matrozova E.A., Pankratov A.L., Gordeeva A.V., Chiginev A.V., Kuzmin L.S.

Kuzmin L.S., Blagodatkin A.V., Mukhin A.S., Pimanov D.A., Zbrozhek V.O., Gordeeva A.V., Pankratov A.L., Chiginev A.V.

We have developed and realized a novel multichroic seashell antenna with internal bandpass filters by resonant slots and cold-electron bolometers (CEB). Slots and CEBs are connected by coplanar waveguides (CPW) instead of microstrip lines to realize the most reliable single-layer technology. The internal resonance is organized by a series resonance of slots with CPW and capacitances of superconductor/insulator/normal (SIN) tunnel junctions. In contrast, a conventional multichroic pixel consists of a wideband sinuous antenna coupled to TES detectors by long microstrip lines with overlap and external on-chip filters for different frequency bands. A common problem with a conventional multichroic pixel is that the beam width is frequency dependent for different frequency bands. Besides that, this system with external filters is quite large and includes long microstrip lines with unavoidable overlap and rater high losses. The multichroic seashell antenna with internal resonances avoids all these problems. The main advantage of this antenna is an opportunity to tune separate pairs of phased slots for each frequency band independently. We used pairs of lambda/2 slots for 75 and 105 GHz, connected by CPW to CEBs. The connection of CPW to slots was shifted closer to the end of slots for proper RF matching. Each CEB included two SIN junctions and an absorber. SIN junctions had capacitances of 77 and 67 fF. Wave impedance of the antenna was near 50 Ohm and resistance of the absorber was matched to this value. RF testing was done at 314 mK irradiating this chip by frequency sweep of a generator from 78-118 GHz. The response curves have shown clear resonances around 75 and 105 GHz with a quality factor around 5. These experiments confirmed that the seashell antenna with the internal filters by resonant slots and CEBs could effectively be used for creating multiband elements.

Mukhin A.S., Kuzmin L.S., Chiginev A.V., Blagodatkin A.V., Zbrozhek V.O., Gordeeva A.V., Pankratov A.L.

A novel type of the seashell slot antenna with internal filters by the capacitance of resonant cold-electron bolometers (RCEB) and kinetic inductance of the NbN superconducting nanostrip has been realized for multifrequency pixels. Seashell antenna gives the opportunity to connect opposite slots by coplanar waveguides (CPW) instead of microstrip lines (MSL). A conventional multifrequency pixel combines a wideband antenna and narrowband filters with long microstrip lines with unavoidable losses and overlaps. Another problem is the frequency dependent beam width due to a fixed pixel diameter for multiple frequencies. The main advantage of the seashell antenna with nano-filters is independent tuning of the separate pairs of slots for each frequency avoiding frequency dependence of the beam width. We used λ/2 slots for 75 and 105 GHz, feeding by CPW near the end of slots for RF matching. Each RCEB includes two SIN (Superconductor-Insulator-Normal) tunnel junctions with a nano-absorber and NbN kinetic inductance of 450 or 310 pH. SIN junctions had capacitances of 9.3 and 7.2 fF and absorber matched to a wave impedance of the antenna near 50 Ohm. Kinetic inductance value was estimated at the level of 35 pH/sq. RF testing was done at 300 mK irradiating this chip by sweep generator from 60 to 120 GHz. The response curves showed clear resonances at 75 and 105 GHz with a quality factor of 10 and 7. These experiments confirm that the seashell antenna with the internal RCEB filters can be used for frequency selection in compact multiband pixels.

Revin L.S., Pankratov A.L., Masterov D.V., Parafin A.E., Pavlov S.A., Chiginev A.V., Rakut’ I.V., Gordeeva A.V., Zbrozhek V.O., Blagodatkin A.V., Kuzmin L.S.

Revin L.S., Pankratov A.L., Masterov D.V., Parafin A.E., Pavlov S.A., Chiginev A.V., Skorokhodov E.V.

We present the results of an experimental and theoretical study of YBCO long Josephson junctions on bicrystal YSZ substrates under the influence of an external magnetic field and under the combined action of a magnetic field and microwave radiation. Samples of YBCO films have been fabricated using the original technology of a preliminary topology mask, leading to critical current densities of order 0.6 MA · cm -2 at a temperature of 6 K. Detailed measurements of the samples were made in the temperature range of 6-90 K, and the wide variety of subharmonic Shapiro steps has been observed and investigated depending on the magnetic field.

Kuzmin L.S., Chiginev A.V.

Two types of planar multichroic antennasMultichroic antenna are reviewed. Frequency and beam characteristics of the antennas are calculated numerically. Both antennas are shown to have characteristics satisfying the ESA requirements.

Kuzmin L.S., Mukhin A.S., Chiginev A.V.

A novel type of the resonant cold-electron bolometer (RCEB) has been realized for multichroic pixels. The internal resonance is organized by a kinetic inductance of the NbN superconducting nanostrip and a capacitance of the superconductor-insulator-normal (SIN) tunnel junctions. The basic idea of a multichroic system is to combine a wideband antenna and narrow-band RCEBs. We used a single Lambda slot with two RCEBs for 75 and 105 GHz, placed in the middle. Each RCEB included two SIN junctions with absorber connected to NbN kinetic inductance of 420 and 240 pH. SIN junctions had capacitances of 11 and 8 fF. Wave impedance of the slot antenna was near 15 Ω and resistance of the absorber was matched to this value. Matching of antenna with an external system was done by placing Si lens on the back side of a Si substrate. RF testing was done at 300 mK irradiating this chip by sweep generator from 60 to 120 GHz. The response curves showed clear resonances at 75 and 105 GHz with quality factor of 10 and 7. Kinetic inductance value was estimated at the level of 35 pH/sq. These experiments confirmed that the RCEB can be effectively used to create multiband elements.

Revin L.S., Pankratov A.L., Chiginev A.V., Masterov D.V., Parafin A.E., Pavlov S.A.

We carry out experimental and theoretical investigations into the effect of the vortex chain propagation on the current–voltage characteristics of YBa2Cu3O7−δ (YBCO) long Josephson junctions. Samples of YBCO Josephson junctions, fabricated on 24° [001]-tilt bicrystal substrates, have been measured. The improved technology has allowed us to observe and study the asymmetry of the current–voltage characteristics with opposite magnetic fields (Revin et al 2012 J. Appl. Phys. 114 243903), which we believe occurs due to anisotropy of bicrystal substrates (Kupriyanov et al (2013 JETP Lett. 95 289)). Specifically, we examine the flux–flow resonant steps versus the external magnetic field, and study the differential resistance and its relation to oscillation power for opposite directions of vortex propagation.

Nakagawa S., Yamada S., Kikuchi R., Minami H., Ishida S., Eisaki H., Kashiwagi T.

The development of a technology for the microfabrication of Bi2Sr2CaCu2O8+δ (Bi2212) crystals is essential for realizing high-performance terahertz emitting devices based on Bi2212 single crystals. We developed an anisotropic wet-etching method using potassium hydroxide solution to improve the etching accuracy of Bi2212 crystal chips. Etching solutions with potassium hydroxide concentration of 10–13 wt. % and temperatures of approximately 40–45 °C are suitable for sample etching. The developed etching method enabled us to obtain crystal chips with sidewall angles of approximately 90°. In the case of a crystal chip with a thickness of ∼6 μm, the undercuts from the edges of the photomask were ∼1.5 μm, which were significantly shorter than those obtained in previous studies using acidic solutions (∼5–10 μm). The etching rate of the developed solution (0.1 μm/min) was lower than that of the acidic solutions (∼20 μm/min), which provided suitable etching conditions for the samples. Devices using Bi2212 crystal chips, fabricated using the developed technique, exhibited clear terahertz emissions, similar to those reported in previous studies. The enhanced accuracy of the proposed etching process is expected to improve the device characteristics of Bi2212 terahertz emitters, particularly in terms of the emission power and frequency.

Revin L.S., Pankratov A.L., Parafin A.E., Masterov D.V., Pavlov S.A., Blagodatkin A.V.

Kikuchi R., Nakagawa S., Enomoto Y., Kuzumi Y., Yamada S., Maeshima K., Yamauchi Y., Minami H., Kashiwagi T.

Understanding the device characteristics associated with the shape and size of crystal chips is a key requirement for developing high-performance terahertz (THz) wave-emitting devices made of high-temperature superconductor Bi2Sr2CaCu2O8+δ(Bi2212) crystal chips, because these parameters reflect the emission frequency, emission power, self-heating conditions, and impedance matching. Wet-etching techniques are beneficial for creating comparable emitting chips from the same crystal fragment to further understand the above points regarding using Bi2212-crystal chips. Using wet-etching techniques, we prepared rectangular crystal chips with the same area using three different width (w) and length (L) aspect ratios and compared their emission characteristics. The range of the observed emission frequencies tended to be less dependent on the w/L ratio. However, the three samples differed significantly in terms of the excitation modes expected from the w/L ratio. When the aspect ratio approached one, the results indicated a tendency to resonate in the higher excitation modes. The excitation modes along the width of the chip were suppressed by decreasing the w/L ratio owing to the increased resonance frequencies of the transverse magnetic TM(m,0) modes. Although further studies are required, especially in terms of output enhancement, the results obtained herein are expected to aid in producing devices that can operate in the desired excitation mode.

Nazhestkin I.A., Bakurskiy S.V., Neilo A.A., Tarasova I.E., Ismailov N.G., Gurtovoi V.L., Egorov S.V., Lisitsyn S.A., Stolyarov V.S., Antonov V.N., Ryazanov V.V., Kupriyanov M.Y., Soloviev I.I., Klenov N.V., Yakovlev D.S.

The transport properties of a nanobridge superconducting quantum interference device made of Al/Pt bilayer have been studied. Measurement and approximation of the voltage‐field dependencies allow to estimate the inductance of the structure. It is found that this value significantly exceeds the expected geometric inductance and exhibits an atypical temperature dependence. To explain this effect, a microscopic model of electron transport in SN bilayers is developed, considering the proximity effect, and the available regimes of the current distribution are described. The measured properties may be indicative of the formation of high‐resistance aluminum with high values of kinetic inductance during the fabrication of Al/Pt bilayers.

Revin L.S., Pimanov D.A., Pankratov A.L., Blagodatkin A.V., Matrozova E.A., Chiginev A.V., Gordeeva A.V., Fedotov I.A., Skorokhodov E.V., Gusev N.S., Masterov D.V., Parafin A.E., Sobolev A.S.

Guarcello C., Maiellaro A., Settino J., Gaiardoni I., Trama M., Romeo F., Citro R.

Guarcello C., Barone C., Carapella G., Granata V., Filatrella G., Giachero A., Pagano S.

Galin M., El'kina A., Levichev M., Masterov D., Parafin A., Revin L.

Matrozova E., Revin L., Chiginev A.

Maiellaro A., Trama M., Settino J., Guarcello C., Romeo F., Citro R.

The superconducting diode effect, reminiscent of the unidirectional charge transport in semiconductor diodes, is characterized by a nonreciprocal, dissipationless flow of Cooper pairs. This remarkable phenomenon arises from the interplay between symmetry constraints and the inherent quantum behavior of superconductors. Here, we explore the geometric control of the diode effect in a kinked nanostrip Josephson junction based on a two-dimensional electron gas (2DEGs) with Rashba spin-orbit interaction. We provide a comprehensive analysis of the diode effect as a function of the kink angle and the out-of-plane magnetic field. Our analysis reveals a rich phase diagram, showcasing a geometry and field-controlled diode effect. The phase diagram also reveals the presence of an anomalous Josephson effect related to the emergence of trivial zero-energy Andreev bound states, which can evolve into Majorana bound states. Our findings indicate that the exceptional synergy between geometric control of the diode effect and topological phases can be effectively leveraged to design and optimize superconducting devices with tailored transport properties.

Kumar S., Khare N.

Abstract YBCO Step edge Josephson junctions are fabricated on single crystal MgO (100) substrates, and the effect of Ar+ ion irradiation on the critical current (Ic) and normal state resistance (Rn) is studied. It is shown that on the appropriate exposure of the YBCO step edge junction to Ar+ ion irradiation, the IcRn product of the junction can be enhanced up to 0.66 mV at 77 K, which is sufficiently good for many applications. With the increase in the exposure time of Ar+ ion irradiation, the value of Ic decreases, and the Rn value increases. After irradiating for 4 min, Ic as low as 70 μA and Rn as high as ∼9.4 Ω have been obtained at 77 K. It is found that for higher exposure time, the junction behavior tends to SIS-type junctions. The mechanism responsible for the decrease in Ic and increase in Rn seems to be associated with the vacancies as well as displacement of oxygen atoms caused by the ion irradiation, which causes the suppression of superconducting parameters as the superconducting properties critically depend on the concentration of the oxygen atoms in the Cu-O planes.

Pankratov A.L., Revin L.S., Pankratova E.V., Shitov S.V.

We present the analysis of soliton dynamics, current–voltage characteristics and AC power for a two-dimensional lattice of Josephson junctions using an effective alternating direction implicit (ADI) numerical scheme. The lattice is supplemented by a resistive-capacitive load (RC-load) and the bias feed is supplied from boundaries of the structure only and is redistributed between junctions via internal dynamics. At fixed length of such a lattice, its critical current have a maximum as a function of a lattice width, since not all junctions inside the lattice can be biased equally. The use of RC-load allows transferring generated AC power to a load device out of the array, but it changes the dynamics significantly. We show that regimes of solitons with plasma tails, generated due to array discreteness and leading to strong superradiant power, become unstable with matched RC-load and the corresponding zero field steps at the current–voltage characteristics disappear completely. Instead, at matched RC-load, standing wave regimes demonstrate high generation efficiency, reaching 21% of supplied dc power.

Kandel H., Arndt N., Li Z., Lee J., Yao Y., Roy S., Cunliffe-Owen H., Reznik D., Eom C.

We have grown and characterized (110)-oriented YBa2Cu3O7−x (YBCO)/PrBa2(Cu0.8Ga0.2)3O7−x (PBCGO) bilayer and YBCO/PBCGO/YBCO trilayer heterostructures, which were deposited by pulsed laser deposition technique for the nanofabrication of (110)-oriented YBCO-based superconductor (S)/insulator (I)/superconductor (S) tunneling vertical geometry Josephson junction and other superconductor electronic devices. The structural properties of these heterostructures, investigated through various x-ray diffraction techniques (profile, x-ray reflectivity, pole figure, and reciprocal mapping), showed (110)-oriented epitaxial growth with a preferred c-axis-in-plane direction for all layers of the heterostructures. The atomic force microscopy measurement on the top surface of the heterostructures showed crack-free and pinhole-free, compact surface morphology with about a few nanometer root mean square roughness over the 5 × 5 μm2 region. The electrical resistivity measurements on the (110)-direction of the heterostructures showed superconducting critical temperature (Tc) values above 77 K and a very small proximity effect due to the interfacial contact of the superconducting YBCO layers with the PBCGO insulating layer. Raman spectroscopy measurements on the heterostructures showed the softening of the Ag-type Raman modes associated with the apical oxygen O(4) and O(2)-O(3)-in-phase vibrations compared to the stand-alone (110)-oriented PBCGO due to the residual stress and additional two Raman modes at ∼600 and ∼285 cm−1 frequencies due to the disorder at the Cu–O chain site of the PBCGO. The growth process and structural, electrical transport, and Raman spectroscopy characterization of (110)-oriented YBCO/PBCGO bilayer and YBCO/PBCGO/YBCO trilayer heterostructures are discussed in detail.

Nakayama M., Nakagawa S., Yamaguchi T., Minami H., Kadowaki K., Nakao H., Mochiku T., Tsujimoto M., Ishida S., Eisaki H., Kashiwagi T.

To obtain high-performance THz-wave-emitting devices made of single crystals of Bi2Sr2CaCu2O8+δ (Bi2212), a high-temperature superconductor, an understanding of the device characteristics based on crystal characteristics can be a key issue because, in principle, the electrical properties of the intrinsic Josephson junctions (IJJs) constructed in Bi2212 crystals highly depend on crystal conditions, such as carrier concentration, crystal homogeneities, and crystal defects. To evaluate the tendencies of the device characteristics associated with crystal characteristics, we prepared Bi2212 crystals with different Bi/Sr ratios (x=0.05, 0.15, and 0.25) and δ values (annealed under N2 or O2 gas flow conditions). The unit cell parameter c decreased as the Bi/Sr ratio or δ increased. For the same annealing conditions under N2 gas flow, the superconducting transition temperature as well as the size of the hysteresis loop of the current–voltage characteristics and emission characteristics were significantly suppressed for the sample with x=0.25 compared with the corresponding values for the samples with x=0.05 and 0.15. The experimental results clearly indicate that parameters, such as the Bi/Sr ratio and annealing conditions, are crucial factors in determining the electrical characteristics of a device. This information can be a useful guide for the preparation of crystals for IJJ THz-wave devices that can be fine-tuned according to the desired device characteristics.

Bogatskaya A.V., Klenov N.V., Popov A.M., Schegolev A.E., Titovets P.A., Tereshonok M.V., Yakovlev D.S.

It is known that the dielectric layer (resonator) located behind the conducting plate of the bolometer system can significantly increase its sensitivity near the resonance frequencies. In this paper, the possibility of receiving broadband electromagnetic signals in a multilayer bolometric meta-material made of alternating conducting (e.g., silicon semiconductor) and dielectric layers is demonstrated both experimentally and numerically. It is shown that such a multilayer structure acts as a lattice of resonators and can significantly increase the width of the frequency band of efficient electromagnetic energy absorption. The parameters of the dielectric and semiconductor layers determine the frequency bands. Numerical modeling of the effect has been carried out under the conditions of our experiment. The numerical results show acceptable qualitative agreement with the experimental data. This study develops the previously proposed technique of resonant absorption of electromagnetic signals in bolometric structures.

Kreidel M., Chu X., Balgley J., Antony A., Verma N., Ingham J., Ranzani L., Queiroz R., Westervelt R.M., Hone J., Fong K.C.

The discovery of van der Waals superconductors in recent years has generated a lot of excitement for their potentially novel pairing mechanisms. However, their typical atomic-scale thickness and micrometer-scale lateral dimensions impose severe challenges to investigations of pairing symmetry by conventional methods. We demonstrate an improved technique that employs high-quality-factor superconducting resonators to measure the kinetic inductance—up to one part per million—and loss of a van der Waals superconductor. We analyze the equivalent circuit model to extract the kinetic inductance, superfluid stiffness, penetration depth, and ratio of imaginary and real parts of the complex conductivity. We validate the technique by measuring aluminum and finding excellent agreement in both the zero-temperature superconducting gap as well as the complex conductivity data when compared with BCS theory. We then demonstrate the utility of the technique by measuring the kinetic inductance of multilayered niobium diselenide and discuss the limits to the accuracy of our technique when the transition temperature of the sample, NbSe2 at 7.06 K, approaches our Nb probe resonator at 8.59 K. Our method will be useful for practitioners in the growing fields of superconducting physics, materials science, and quantum sensing, as a means of characterizing superconducting circuit components and studying pairing mechanisms of the novel superconducting states which arise in layered two-dimensional materials and heterostructures. Published by the American Physical Society 2024

Regnier M., Manzan E., Hamilton J., Mennella A., Errard J., Zapelli L., Torchinsky S.A., Paradiso S., Battistelli E., De Bernardis P., Colombo L., De Petris M., D’Alessandro G., Garcia B., Gervasi M., et. al.

Context. Astrophysical polarized foregrounds represent the most critical challenge in cosmic microwave background (CMB) B-mode experiments, requiring multifrequency observations to constrain astrophysical foregrounds and isolate the CMB signal. However, recent observations indicate that foreground emission may be more complex than anticipated. Not properly accounting for these complexities during component separation can lead to a bias in the recovered tensor-to-scalar ratio. Aims. In this paper we investigate how the increased spectral resolution provided by band-splitting in bolometric interferometry (BI) through a technique called spectral imaging can help control the foreground contamination in the case of an unaccounted-for Galactic dust frequency de-correlation along the line of sight (LOS). Methods. We focused on the next-generation ground-based CMB experiment CMB-S4 and compared its anticipated sensitivity, frequency, and sky coverage with a hypothetical version of the same experiment based on BI (CMB-S4/BI). We performed a Monte Carlo analysis based on parametric component separation methods (FGBuster and Commander) and computed the likelihood of the recovered tensor-to-scalar ratio, r. Results. The main result is that spectral imaging allows us to detect systematic uncertainties on r from frequency de-correlation when this effect is not accounted for in the component separation. Conversely, an imager such as CMB-S4 would detect a biased value of r and would be unable to spot the presence of a systematic effect. We find a similar result in the reconstruction of the dust spectral index, and we show that with BI we can more precisely measure the dust spectral index when frequency de-correlation is present and not accounted for in the component separation. Conclusions. The in-band frequency resolution provided by BI allows us to identify dust LOS frequency de-correlation residuals where an imager with a similar level of performance would fail. This creates the possibility of exploiting this potential in the context of future CMB polarization experiments that will be challenged by complex foregrounds in their quest for B-mode detection.

Lemziakov S.A., Karimi B., Nakamura S., Lvov D.S., Upadhyay R., Satrya C.D., Chen Z.-., Subero D., Chang Y.-., Wang L.B., Pekola J.P.

AbstractThe importance and non-trivial properties of superconductor normal metal interfaces were discovered by Alexander Fyodorovich Andreev more than 60 years ago. Only much later, these hybrids have found wide interest in applications such as thermometry and refrigeration, electrical metrology, and quantum circuit engineering. Here we discuss the central properties of such interfaces and describe some of the most prominent and recent applications of them.

Likhachev S.F., Larchenkova T.I.

Sushkov A.O.

In the quest for solving the dark-matter puzzle, quantum engineering strategies for improving detection sensitivity are discussed.

Kalacheva D., Fedorov G., Khrapach I., Astafiev O.

Abstract We present a model and experimental realization of coplanar superconducting resonators terminated by a shunting kinetic inductance bridge made of ultra-thin Al films. The fabrication process that we propose allows us to create very homogeneous films, which makes them suitable for many applications in quantum devices. Due to the specific properties of the films, the resonators exhibit a Duffing oscillator behavior resulting in bifurcations and interactions between different power sources, which was previously observed in similar systems. Moreover, since the nonlinearity of such a system is concentrated at the bridge, while the wave propagates in a linear environment, it is possible to propose a simple model that accurately describes its behavior. We show that, when resonators are operated within a notch-port architecture, our model has a closed-form solution for the transmission coefficient and allows one to accurately extract parameters of the system, including the kinetic inductance of the bridge and its depairing current. Potential applications of such systems include tunable resonators, photon detectors, bifurcation and parametric amplifiers, as well as a measurement device for studying the properties of thin films.

Moskalev D.O., Zikiy E.V., Pishchimova A.A., Ezenkova D.A., Smirnov N.S., Ivanov A.I., Korshakov N.D., Rodionov I.A.

AbstractThe most commonly used physical realization of superconducting qubits for quantum circuits is a transmon. There are a number of superconducting quantum circuits applications, where Josephson junction critical current reproducibility over a chip is crucial. Here, we report on a robust chip scale Al/AlOx/Al junctions fabrication method due to comprehensive study of shadow evaporation and oxidation steps. We experimentally demonstrate the evidence of optimal Josephson junction electrodes thickness, deposition rate and deposition angle, which ensure minimal electrode surface and line edge roughness. The influence of oxidation method, pressure and time on critical current reproducibility is determined. With the proposed method we demonstrate Al/AlOx/Al junction fabrication with the critical current variation $$(\sigma /\langle {I_{c} } \rangle )$$ ( σ / ⟨ I c ⟩ ) less than 3.9% (from 150 × 200 to 150 × 600 nm2 area) and 7.7% (for 100 × 100 nm2 area) over 20 × 20 mm2 chip. Finally, we fabricate separately three 5 × 10 mm2 chips with 18 transmon qubits (near 4.3 GHz frequency) showing less than 1.9% frequency variation between qubits on different chips. The proposed approach and optimization criteria can be utilized for a robust wafer-scale superconducting qubit circuits fabrication.

Withington S.

Revin L.S., Masterov D.V., Parafin A.E., Pavlov S.A., Pimanov D.A., Chiginev A.V., Blagodatkin A.V., Rakut’ I.V., Skorokhodov E.V., Gordeeva A.V., Pankratov A.L.

The resonant properties of Cold-Electron Bolometers (CEBs) located at a 0.3 K cryostat plate are measured using a 50 μm long high-temperature YBa2Cu3O7−δ (YBCO) Josephson junction oscillator, placed on a 2.7 K plate of the same cryostat. For these purposes, a bunch of YBCO Josephson oscillators with various lengths of dipole antennas and overlapping generation bands has been developed and investigated in 50–500 GHz frequency range. Two setups of Josephson junction placement were compared, and as a result, various narrow-band receiving systems with CEBs have been measured, demonstrating the feasibility of the presented approach.

Allys E., Arnold K., Aumont J., Aurlien R., Azzoni S., Baccigalupi C., Banday A.J., Banerji R., Barreiro R.B., Bartolo N., Bautista L., Beck D., Beckman S., Bersanelli M., Boulanger F., et. al.

Abstract LiteBIRD the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun-Earth Lagrangian point L2, where it will map the cosmic microwave background (CMB) polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of 2.2 μK-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions and synergies with other projects. Subject Index LiteBIRD cosmic inflation, cosmic microwave background, B-mode polarization, primordial gravitational waves, quantum gravity, space telescope

Pimanov D.A., Frost V.A., Blagodatkin A.V., Gordeeva A.V., Pankratov A.L., Kuzmin L.S.

Electron on-chip cooling from the base temperature of 300 mK is very important for highly sensitive detectors operating in space due to problems of dilution fridges at low gravity. Electron cooling is also important for ground-based telescopes equipped with 3He cryostats being able to function at any operating angle. This work is aimed at the investigation of electron cooling in the low-temperature range. New samples of cold-electron bolometers with traps and hybrid superconducting/ferromagnetic absorbers have shown a temperature reduction of the electrons in the refrigerator junctions from 300 to 82 mK, from 200 to 33 mK, and from 100 to 25 mK in the idle regime without optical power load. The electron temperature was determined by solving heat balance equations with account of the leakage current, sixth power of temperature in the whole temperature range, and the Andreev current using numerical methods and an automatic fit algorithm.

Chiginev A.V., Blagodatkin A.V., Pimanov D.A., Matrozova E.A., Gordeeva A.V., Pankratov A.L., Kuzmin L.S.

Here we present the results of a numerical modeling of mode composition in the constriction of the Large Scale Polarization Explorer-Short-Wavelength Instrument for the Polarization Explorer (LSPE-SWIPE) back-to-back horn. These results are used for calculating the frequency response of arrays of planar dipole antennas with cold-electron bolometers for 145, 210, and 240 GHz frequencies. For the main frequency channel (i.e., 145 GHz) we have a 45 GHz bandwidth. For the auxiliary frequency channels (i.e., 210 and 240 GHz) placed on the same substrate, we have bandwidths of 26 and 38 GHz, respectively. We performed some optimizations for cold-electron bolometers to achieve a photon noise-equivalent power of 1.1 × 10−16 W/Hz1/2. This was achieved by replacing one of two superconductor–insulator–normal tunnel junctions with a superconductor–normal metal contact.

D’Alessandro G., Battistelli E.S., de Bernardis P., De Petris M., Gamboa Lerena M.M., Grandsire L., Hamilton J.-., Marnieros S., Masi S., Mennella A., Mousset L., O’Sullivan C., Piat M., Tartari A., Torchinsky S.A., et. al.

The Q & U Bolometric Interferometer for Cosmology (QUBIC) is a cosmology experiment that aims to measure the B-mode polarization of the cosmic microwave background (CMB). Measurements of the primordial B-mode pattern of the CMB polarization are in fact among the most exciting goals in cosmology as it would allow testing of the inflationary paradigm. Many experiments are attempting to measure the B-modes, from the ground and the stratosphere, using imaging Stokes polarimeters. The QUBIC collaboration developed an innovative concept to measure CMB polarization using bolometric interferometry. This approach mixes the high sensitivity of bolometric detectors with the accurate control of systematics due to the interferometric layout of the instrument. We present the calibration results for the Technological Demonstrator, before its commissioning in the Argentinian observing site and preparation for first light.

Healy E., Dutcher D., Atkins Z., Austermann J., Choi S.K., Duell C.J., Duff S., Galitzki N., Huber Z.B., Hubmayr J., Johnson B.R., McCarrick H., Niemack M.D., Sonka R., Staggs S.T., et. al.

The Simons Observatory (SO) will detect and map the temperature and polarization of the millimeter-wavelength sky from Cerro Toco, Chile, across a range of angular scales, providing rich data sets for cosmological and astrophysical analysis. The SO focal planes will be tiled with compact hexagonal packages, called universal focal-plane modules (UFMs), in which the transition-edge sensor (TES) detectors are coupled to 100 mK microwave-multiplexing electronics. Three different types of dichroic TES detector arrays with bands centered at 30/40, 90/150, and 220/280 GHz will be implemented across the 49 planned UFMs. The 90/150 GHz and 220/280 GHz arrays each contain 1764 TESes, which are read out with two 910x multiplexer circuits. The modules contain a series of routed silicon chips, which are packaged together in a controlled electromagnetic environment and operated at 100 mK. Following an overview of the module design, we report on early results from the first 220/280 GHz UFM, including detector yield, as well as readout and detector noise levels.

Kuzmin L., Golubev D.S.

An optimized concept of the Cold-Electron Bolometer (CEB) with Superconductor-Insulator-Normal (SIN) Tunnel Junction and Andreev SN contact for voltage-bias mode has been developed. The responsivity of this design is much better than the widespread concept of the CEB with two SIN tunnel junctions for the current-biased mode (SINIS structure) due to degradation of responsivity by a factor of two in voltage-bias (VB) mode. Besides that, for the realization of the CEB with the same capacitance, we need twice larger junctions that lead to four times larger area and volume of the absorber. As a result, the NEP of one SIN junction CEB is half that of two SIN junction CEB. A novel concept of the quasiparticle cascade amplifier (QCA) based on harvesting the waste energy of relaxed quasiparticles without any additional voltage bias has been developed. The distinguish feature of the cascade principle is utilizing the same dc voltage as used for CEB. The cascade principle of signal amplification proved to be possible due to the conversion of electrons to holes in the second absorber. The amplifier is based on the optimized CEB with one SIN junction and one SN contact. The coefficient of power amplification of the incoming signal to the potential energy of hot quasiparticles is huge and can achieve a level of 140 at the optimal bias point. The coefficient of power amplification of the QCA can reach a value of 30 and more to overcome the noise of the SQUID amplifier. For a power load of 6 pW, the total NEP of the CEB is decreased to the level of photon noise NEP, down to 0.7*NEP phot .