| Records |
| Author |
Yang, Y.; Fedorov, G.; Shafranjuk, S. E.; Klapwijk, T. M.; Cooper, B. K.; Lewis, R. M.; Lobb, C. J.; Barbara, P. |
| Title |
Electronic transport and possible superconductivity at Van Hove singularities in carbon nanotubes |
Type |
Journal Article |
| Year |
2015 |
Publication |
Nano Lett. |
Abbreviated Journal |
Nano Lett. |
| Volume |
15 |
Issue |
12 |
Pages |
7859-7866 |
| Keywords |
carbon nanotubes, CNT, tunable superconductivity, van Hove singularities |
| Abstract |
Van Hove singularities (VHSs) are a hallmark of reduced dimensionality, leading to a divergent density of states in one and two dimensions and predictions of new electronic properties when the Fermi energy is close to these divergences. In carbon nanotubes, VHSs mark the onset of new subbands. They are elusive in standard electronic transport characterization measurements because they do not typically appear as notable features and therefore their effect on the nanotube conductance is largely unexplored. Here we report conductance measurements of carbon nanotubes where VHSs are clearly revealed by interference patterns of the electronic wave functions, showing both a sharp increase of quantum capacitance, and a sharp reduction of energy level spacing, consistent with an upsurge of density of states. At VHSs, we also measure an anomalous increase of conductance below a temperature of about 30 K. We argue that this transport feature is consistent with the formation of Cooper pairs in the nanotube. |
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Department of Physics, Georgetown University , Washington, District of Columbia 20057, United States |
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1530-6984 |
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PMID:26506109; Suuplementary info (attached to pdf) DOI: 10.1021/acs.nanolett.5b02564 |
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1782 |
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Baselmans, J.; Kooi, J.; Baryshev, A.; Yang, Z. Q.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; Voronov, B.; Gol’tsman, G. |
| Title |
Full characterization of small volume NbN HEB mixers for space applications |
Type |
Conference Article |
| Year |
2005 |
Publication |
Proc. 16th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 16th Int. Symp. Space Terahertz Technol. |
| Volume |
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Pages |
457-462 |
| Keywords |
NbN HEB mixers |
| Abstract |
NbN phonon cooled HEB’s are one of the most promising bolometer mixer technologies for (near) future (space) applications. Their performance is usually quantified by mea- suring the receiver noise temperature at a given IF frequency, usually around 1 – 2 GHz. However, for any real applications it is vital that one fully knows all the relevant properties of the mixer, including LO power, stability, direct detection, gain bandwidth and noise bandwidth, not only the noise temperature at low IF frequencies. To this aim we have measured all these parameters at the optimal operating point of one single, small volume quasioptical NbN HEB mixer. We find a minimum noise temperature of 900 K at 1.46 THz. We observe a direct detection effect indicated by a change in bias current when changing from a 300 K hot load to a 77 K cold load. Due to this effect we overestimate the noise temperature by about 22% using a 300 K hot load and a 77 K cold load. The LO power needed to reach the optimal operating point is 80 nW at the receiver lens front, 59 nW inside the NbN bridge. However, using the isothermal technique we find a power absorbed in the NbN bridge of 25 nW, a difference of about a factor 2. We obtain a gain bandwidth of 2.3 GHz and a noise bandwidth of 4 GHz. The system Allan time is about 1 sec. in a 50 MHz spectral bandwidth and a deviation from white noise integration (governed by the radiometer equation) occurs at 0.2 sec., which implies a maximum integration time of a few seconds in a 1 MHz bandwidth spectrometer. |
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Göteborg, Sweden |
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363 |
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Gao, G. R.; Hovenier, J. N.; Yang, Z. Q.; Baselmans, J. J. A.; Baryshev, A.; Hajenius, M.; Klapwijk, T. M.; Adam, A. J. L.; Klaassen, T. O.; Williams, B. S.; Kumar, S.; Hu, Q.; Reno, J. L. |
| Title |
A novel terahertz heterodyne receiver based on a quantum cascade laser and a superconducting bolometer |
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Conference Article |
| Year |
2005 |
Publication |
Proc. 16th Int. Symp. Space Terahertz Technol. |
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19-23 |
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Göteborg, Sweden |
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RPLAB @ s @ qc_lasers_gao_isstt16 |
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367 |
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Gao, J. R.; Hajenius, M.; Baselmans, J. J. A.; Klapwijk, T. M.; de Korte, P. A. J.; Voronov, B.; Gol'tsman, G. |
| Title |
NbN hot electron bolometer mixers with superior performance for space applications |
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Conference Article |
| Year |
2004 |
Publication |
Proc. Int. workshop on low temp. electronics |
Abbreviated Journal |
Proc. Int. workshop on low temp. electronics |
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Issue |
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Pages |
11-17 |
| Keywords |
NbN HEB mixers, applications |
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Noordwijk |
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Armandillo, E.; Leone, B. |
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International workshop on low temperature electronics- WOLTE 6 - Noordwijk |
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no |
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1496 |
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Hajenius, M.; Baselmans, J. J. A.; Gao, J. R.; Klapwijk, T. M.; de Korte, P. A. J.; Voronov, B.; Gol’tsman, G. |
| Title |
Improved NbN phonon cooled hot electron bolometer mixers |
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Conference Article |
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2003 |
Publication |
Proc. 14th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 14th Int. Symp. Space Terahertz Technol. |
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413-423 |
| Keywords |
NbN HEB mixers |
| Abstract |
NbN phonon-cooled hot electron bolometer mixers (HEBs) have been realized with negligible contact resistance to Au pads. By adding either a 5 nm Nb or a 10 nm NbTiN layer between the Au and NbN, to preserve superconductivity in the NbN under the Au contact pad, superior noise temperatures have been obtained. Using DC I,V curves and resistive transitions in combination with process parameters we analyze the nature of these improved devices and determine interface transparencies. |
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Tucson, USA |
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337 |
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