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| Author |
Santhanam, P.; Wind, S.; Prober, D. E. |
| Title |
Localization, superconducting fluctuations, and superconductivity in thin films and narrow wires of aluminum |
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Journal Article |
| Year |
1987 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
| Volume |
35 |
Issue  |
7 |
Pages |
3188-3206 |
| Keywords |
Al films; electron-phonon scattering; electron-electron scattering; Disordered structures; amorphous and glassy solids, Relaxation times and mean free paths, Galvanomagnetic and other magnetotransport effects |
| Abstract |
We report a comprehensive set of experiments on wide and narrow thin-film strips of aluminum which test the predictions of recent localization theory. The experiments on wide films in the two-dimensional regime confirm the theoretical predictions and also yield insight into inelastic mechanisms and spin-orbit scattering rates. Our extension of the existing theory for one-dimensional systems to include spin-orbit scattering and Maki-Thompson superconducting fluctuations is verified by the experiments. We find clear evidence for one-dimensional localization, with inferred inelastic rates identical to those in two-dimensional films. The prediction of the localization theory for a dimensional crossover from two-dimensional to one-dimensional behavior is also confirmed. We have reanalyzed the results of some previous experiments on thin films and narrow wires in light of these results. |
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RPLAB @ gujma @ |
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757 |
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Siddiqi, I.; Prober, D. E. |
| Title |
Nb–Au bilayer hot-electron bolometers for low-noise THz heterodyne detection |
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Journal Article |
| Year |
2004 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
84 |
Issue |
8 |
Pages |
1404 |
| Keywords |
HEB, mixers, dynamic range, saturation, LO power, local oscillator power, Nb |
| Abstract |
The sensitivity of present Nb diffusion-cooled hot-electron bolometer (HEB) mixers is not quantum limited, and can be improved by reducing the superconducting transition temperature TC. Lowering TC reduces thermal fluctuations, resulting in a decrease of the mixer noise temperature TM. However, lower TC mixers have reduced dynamic range and saturate more easily due to background noise. We present 30 GHz microwave measurements on a bilayer HEB system, Nb–Au, in which TC can be tuned with Au layer thickness to obtain the maximum sensitivity for a given noise background. These measurements are intended as a guide for the optimization of THz mixers. Using a Nb–Au mixer with TC = 1.6 K, we obtain TM = 50 K with 2 nW of local oscillator (LO) power. Good mixer performance is observed over a wide range of LO power and bias voltage and such a device should not exhibit saturation in a THz receiver. |
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0003-6951 |
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