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Author Anthore, A.; Pothier, H.; Esteve, D.
Title Density of states in a superconductor carrying a supercurrent Type Journal Article
Year 2003 Publication Phys. Rev. Lett. Abbreviated Journal Phys. Rev. Lett.
Volume 90 Issue (up) 12 Pages 127001 (1 to 4)
Keywords Usadel, superconducting nanowire
Abstract We have measured the tunneling density of states (DOS) in a superconductor carrying a supercurrent or exposed to an external magnetic field. The pair correlations are weakened by the supercurrent, leading to a modification of the DOS and to a reduction of the gap. As predicted by the theory of superconductivity in diffusive metals, we find that this effect is similar to that of an external magnetic field.
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Notes Recommended by Klapwijk Approved no
Call Number Serial 924
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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 (up) 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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ISSN 0163-1829 ISBN Medium
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Notes Approved no
Call Number Serial 1519
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Author Zhang, J.; Boiadjieva, N.; Chulkova, G.; Deslandes, H.; Gol'tsman, G. N.; Korneev, A.; Kouminov, P.; Leibowitz, M.; Lo, W.; Malinsky, R.; Okunev, O.; Pearlman, A.; Slysz, W.; Smirnov, K.; Tsao, C.; Verevkin, A.; Voronov, B.; Wilsher, K.; Sobolewski, R.
Title Noninvasive CMOS circuit testing with NbN superconducting single-photon detectors Type Journal Article
Year 2003 Publication Electron. Lett. Abbreviated Journal Electron. Lett.
Volume 39 Issue (up) 14 Pages 1086-1088
Keywords NbN SSPD, SNSPD, applications
Abstract The 3.5 nm thick-film, meander-structured NbN superconducting single-photon detectors have been implemented in the CMOS circuit-testing system based on the detection of near-infrared photon emission from switching transistors and have significantly improved the performance of the system. Photon emissions from both p- and n-MOS transistors have been observed.
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ISSN 0013-5194 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1512
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Author Sobolewski, R.; Verevkin, A.; Gol'tsman, G.N.; Lipatov, A.; Wilsher, K.
Title Ultrafast superconducting single-photon optical detectors and their applications Type Journal Article
Year 2003 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal
Volume 13 Issue (up) 2 Pages 1151-1157
Keywords NbN SSPD, SNSPD
Abstract We present a new class of ultrafast single-photon detectors for counting both visible and infrared photons. The detection mechanism is based on photon-induced hotspot formation, which forces the supercurrent redistribution and leads to the appearance of a transient resistive barrier across an ultrathin, submicrometer-width, superconducting stripe. The devices were fabricated from 3.5-nm- and 10-nm-thick NbN films, patterned into <200-nm-wide stripes in the 4 /spl times/ 4-/spl mu/m/sup 2/ or 10 /spl times/ 10-/spl mu/m/sup 2/ meander-type geometry, and operated at 4.2 K, well below the NbN critical temperature (T/sub c/=10-11 K). Continuous-wave and pulsed-laser optical sources in the 400-nm-to 3500-nm-wavelength range were used to determine the detector performance in the photon-counting mode. Experimental quantum efficiency was found to exponentially depend on the photon wavelength, and for our best, 3.5-nm-thick, 100-/spl mu/m/sup 2/-area devices varied from >10% for 405-nm radiation to 3.5% for 1550-nm photons. The detector response time and jitter were /spl sim/100 ps and 35 ps, respectively, and were acquisition system limited. The dark counts were below 0.01 per second at optimal biasing. In terms of the counting rate, jitter, and dark counts, the NbN single-photon detectors significantly outperform their semiconductor counterparts. Already-identified applications for our devices range from noncontact testing of semiconductor CMOS VLSI circuits to free-space quantum cryptography and communications.
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ISSN 1051-8223 ISBN Medium
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Notes Approved no
Call Number Serial 509
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Author Meledin, D.; Tong, C. Y.-E.; Blundell, R.; Kaurova, N.; Smirnov, K.; Voronov, B.; Gol'tsman, G.
Title Study of the IF bandwidth of NbN HEB mixers based on crystalline quartz substrate with an MgO buffer layer Type Journal Article
Year 2003 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 13 Issue (up) 2 Pages 164-167
Keywords NbN HEB mixer
Abstract In this paper, we present the results of IF bandwidth measurements on 3-4 nm thick NbN hot electron bolometer waveguide mixers, which have been fabricated on a 200-nm thick MgO buffer layer deposited on a crystalline quartz substrate. The 3-dB IF bandwidth, measured at an LO frequency of 0.81 THz, is 3.7 GHz at the optimal bias point for low noise receiver operation. We have also made measurements of the IF dynamic impedance, which allow us to evaluate the intrinsic electron temperature relaxation time and self-heating parameters at different bias conditions.
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Notes Approved no
Call Number Serial 341
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