Records |
Author |
Zhang, J.; Słysz, W.; Pearlman, A.; Verevkin, A.; Sobolewski, R.; Okunev, O.; Chulkova, G.; Gol’tsman, G. N. |
Title |
Time delay of resistive-state formation in superconducting stripes excited by single optical photons |
Type |
Journal Article |
Year |
2003 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
67 |
Issue |
13 |
Pages |
132508 (1 to 4) |
Keywords |
NbN SSPD, SNSPD |
Abstract |
We have observed a 65(±5)-ps time delay in the onset of a resistive-state formation in 10-nm-thick, 130-nm-wide NbN superconducting stripes exposed to single photons. The delay in the photoresponse decreased to zero when the stripe was irradiated by multi-photon (classical) optical pulses. Our NbN structures were kept at 4.2 K, well below the material’s critical temperature, and were illuminated by 100-fs-wide optical pulses. The time-delay phenomenon has been explained within the framework of a model based on photon-induced generation of a hotspot in the superconducting stripe and subsequent, supercurrent-assisted, resistive-state formation across the entire stripe cross section. The measured time delays in both the single-photon and two-photon detection regimes agree well with theoretical predictions of the resistive-state dynamics in one-dimensional superconducting stripes. |
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0163-1829 |
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1519 |
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Author |
Ciulin, V.; Carter, S. G.; Sherwin, M. S. |
Title |
Terahertz optical mixing in biased GaAs single quantum wells |
Type |
Journal Article |
Year |
2004 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
70 |
Issue |
11 |
Pages |
115312-(1-6) |
Keywords |
optical mixing |
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1098-0121 |
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501 |
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Author |
Lusche, R.; Semenov, A.; Korneeva, Y.; Trifonov, A.; Korneev, A.; Gol'tsman, G.; Hübers, H.-W. |
Title |
Effect of magnetic field on the photon detection in thin superconducting meander structures |
Type |
Journal Article |
Year |
2014 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
89 |
Issue |
10 |
Pages |
104513 (1 to 7) |
Keywords |
NbN SSPD, SNSPD |
Abstract |
We have studied the influence of an externally applied magnetic field on the photon and dark count rates of meander-type niobium nitride superconducting nanowire single-photon detectors. Measurements have been performed at a temperature of 4.2 K, and magnetic fields up to 250 mT have been applied perpendicularly to the meander plane. While photon count rates are field independent at weak applied fields, they show a strong dependence at fields starting from approximately ±25 mT. This behavior, as well as the magnetic field dependence of the dark count rates, is in good agreement with the recent theoretical model of vortex-assisted photon detection and spontaneous vortex crossing in narrow superconducting lines. However, the local reduction of the superconducting free energy due to photon absorption, which is the fitting parameter in the model, increases much slower with the photon energy than the model predicts. Furthermore, changes in the free-energy during photon counts and dark counts depend differently on the current that flows through the meander. This indicates that photon counts and dark counts occur in different parts of the meander. |
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1098-0121 |
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1367 |
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Author |
Vodolazov, D. Y.; Korneeva, Y. P.; Semenov, A. V.; Korneev, A. A.; Goltsman, G. N. |
Title |
Vortex-assisted mechanism of photon counting in a superconducting nanowire single-photon detector revealed by external magnetic field |
Type |
Journal Article |
Year |
2015 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
92 |
Issue |
10 |
Pages |
104503 (1 to 9) |
Keywords |
SSPD, SNSPD |
Abstract |
We use an external magnetic field to probe the detection mechanism of a superconducting nanowire single-photon detector. We argue that the hot belt model (which assumes partial suppression of the superconducting order parameter Δ across the whole width of the superconducting nanowire after absorption of the photon) does not explain observed weak-field dependence of the photon count rate (PCR) for photons with λ=450nm and noticeable decrease of PCR (with increasing the magnetic field) in a range of the currents for photons with wavelengths λ=450–1200nm. Found experimental results for all studied wavelengths can be explained by the vortex hot spot model (which assumes partial suppression of Δ in the area with size smaller than the width of the nanowire) if one takes into account nucleation and entrance of the vortices to the photon induced hot spot and their pinning by the hot spot with relatively large size and strongly suppressed Δ. |
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1098-0121 |
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no |
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1343 |
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Author |
Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol’tsman, G. |
Title |
One-dimensional resistive states in quasi-two-dimensional superconductors: Experiment and theory |
Type |
Journal Article |
Year |
2007 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
76 |
Issue |
9 |
Pages |
094521 (1 to 5) |
Keywords |
uasi-two-dimensional superconductors, NbN |
Abstract |
We investigate competition between one- and two-dimensional topological excitations—phase slips and vortices—in the formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature TC0. The widths w=100nm of our ultrathin NbN samples are substantially larger than the Ginzburg-Landau coherence length ξ=4nm, and the fluctuation resistivity above TC0 has a two-dimensional character. However, our data show that the resistivity below TC0 is produced by one-dimensional excitations—thermally activated phase slip strips (PSSs) overlapping the sample cross section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current and/or temperature variations. Measuring the resistivity within 7 orders of magnitude, we find that the quantum phase slips can only be essential below this level. |
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1098-0121 |
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no |
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1423 |
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Kardakova, A.; Shishkin, A.; Semenov, A.; Goltsman, G. N.; Ryabchun, S.; Klapwijk, T. M.; Bousquet, J.; Eon, D.; Sacépé, B.; Klein, T.; Bustarret, E. |
Title |
Relaxation of the resistive superconducting state in boron-doped diamond films |
Type |
Journal Article |
Year |
2016 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
93 |
Issue |
6 |
Pages |
064506 |
Keywords |
boron-doped diamond films, resistive superconducting state, relaxation time |
Abstract |
We report a study of the relaxation time of the restoration of the resistive superconducting state in single crystalline boron-doped diamond using amplitude-modulated absorption of (sub-)THz radiation (AMAR). The films grown on an insulating diamond substrate have a low carrier density of about 2.5×1021cm−3 and a critical temperature of about 2K. By changing the modulation frequency we find a high-frequency rolloff which we associate with the characteristic time of energy relaxation between the electron and the phonon systems or the relaxation time for nonequilibrium superconductivity. Our main result is that the electron-phonon scattering time varies clearly as T−2, over the accessible temperature range of 1.7 to 2.2 K. In addition, we find, upon approaching the critical temperature Tc, evidence for an increasing relaxation time on both sides of Tc. |
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2469-9950 |
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1167 |
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Zhang, X.; Lita, A. E.; Smirnov, K.; Liu, H. L.; Zhu, D.; Verma, V. B.; Nam, S. W.; Schilling, A. |
Title |
Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields |
Type |
Journal Article |
Year |
2020 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
101 |
Issue |
6 |
Pages |
060508 (1 to 6) |
Keywords |
MoSi, WSi films |
Abstract |
We have investigated a series of superconducting bridges based on homogeneous amorphous WSi and MoSi films, with bridge widths w ranging from 2 to 1000μm and film thicknesses d∼4−6 and 100 nm. Upon decreasing the bridge widths below the respective Pearl lengths, we observe in all cases distinct changes in the characteristics of the resistive transitions to superconductivity. For each of the films, the resistivity curves R(B,T) separate at a well-defined and field-dependent temperature T∗(B) with decreasing the temperature, resulting in a dramatic suppression of the resistivity and a sharpening of the transitions with decreasing bridge width w. The associated excess conductivity in all the bridges scales as 1/w, which may suggest either the presence of a highly conducting region that is dominating the electric transport, or a change in the vortex dynamics in narrow enough bridges. We argue that this effect can only be observed in materials with sufficiently weak vortex pinning. |
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2469-9950 |
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no |
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1800 |
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Sidorova, M.; Semenov, Alexej D.; Hübers, H.-W.; Ilin, K.; Siegel, M.; Charaev, I.; Moshkova, M.; Kaurova, N.; Goltsman, G. N.; Zhang, X.; Schilling, A. |
Title |
Electron energy relaxation in disordered superconducting NbN films |
Type |
Journal Article |
Year |
2020 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
102 |
Issue |
5 |
Pages |
054501 (1 to 15) |
Keywords |
NbN SSPD, SNSPD, HEB, bandwidth, relaxation time |
Abstract |
We report on the inelastic-scattering rate of electrons on phonons and relaxation of electron energy studied by means of magnetoconductance, and photoresponse, respectively, in a series of strongly disordered superconducting NbN films. The studied films with thicknesses in the range from 3 to 33 nm are characterized by different Ioffe-Regel parameters but an almost constant product qTl (qT is the wave vector of thermal phonons and l is the elastic mean free path of electrons). In the temperature range 14–30 K, the electron-phonon scattering rates obey temperature dependencies close to the power law 1/τe−ph∼Tn with the exponents n≈3.2–3.8. We found that in this temperature range τe−ph and n of studied films vary weakly with the thickness and square resistance. At 10 K electron-phonon scattering times are in the range 11.9–17.5 ps. The data extracted from magnetoconductance measurements were used to describe the experimental photoresponse with the two-temperature model. For thick films, the photoresponse is reasonably well described without fitting parameters, however, for thinner films, the fit requires a smaller heat capacity of phonons. We attribute this finding to the reduced density of phonon states in thin films at low temperatures. We also show that the estimated Debye temperature in the studied NbN films is noticeably smaller than in bulk material. |
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1266 |
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Author |
Il’in, K.S.; Ptitsina, N.G.; Sergeev, A.V.; Gol’tsman, G.N.; Gershenzon, E.M.; Karasik, B.S.; Pechen, E.V.; Krasnosvobodtsev, S.I. |
Title |
Interrelation of resistivity and inelastic electron-phonon scattering rate in impure NbC films |
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Journal Article |
Year |
1998 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
57 |
Issue |
24 |
Pages |
15623-15628 |
Keywords |
NbC films |
Abstract |
A complex study of the electron-phonon interaction in thin NbC films with electron mean free path l=2–13nm gives strong evidence that electron scattering is significantly modified due to the interference between electron-phonon and elastic electron scattering from impurities. The interference T2 term, which is proportional to the residual resistivity, dominates over the Bloch-Grüneisen contribution to resistivity at low temperatures up to 60 K. The electron energy relaxation rate is directly measured via the relaxation of hot electrons heated by modulated electromagnetic radiation. In the temperature range 1.5–10 K the relaxation rate shows a weak dependence on the electron mean free path and strong temperature dependence ∼Tn, with the exponent n=2.5–3. This behavior is explained well by the theory of the electron-phonon-impurity interference taking into account the electron coupling with transverse phonons determined from the resistivity data. |
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0163-1829 |
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no |
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1585 |
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Author |
Heslinga, D. R.; Shafranjuk, S. E.; van Kempen, H.; Klapwijk, T. M. |
Title |
Observation of double-gap-edge Andreev reflection at Si/Nb interfaces by point-contact spectroscopy |
Type |
Journal Article |
Year |
1994 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
Volume |
49 |
Issue |
15 |
Pages |
10484-10494 |
Keywords |
Nb, Si, Nb-Si, Nb/Si, Si/Nb, Andreev reflection, point-contact spectroscopy |
Abstract |
Andreev reflection point-contact spectroscopy is performed on a bilayer consisting of 50-nm degenerately doped Si backed with Nb. Due to the short mean free path both injection into and transport across the Si layer are diffusive, in contrast to the ballistic conditions prevailing in clean metal layers. Nevertheless a large Andreev signal is observed in the point-contact characteristics, not reduced by elastic scattering in the Si layer or by interface scattering, but only limited by the transmission coefficient of the metal-semiconductor point contact. Two peaks in the Andreev reflection probability are visible, marking the values of the superconducting energy gap at the interface on the Nb and Si sides. This interpretation is supported by a method of solving the Bogolubov equations analytically using a simplified expression for the variation of the order parameter close to the interface. This observation enables a comparison with theoretical predictions of the gap discontinuity in the proximity effect. It is found that the widely used de Gennes model does not agree with the experimental data. |
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American Physical Society |
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1005 |
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