Latest Research Papers In Condensed Matter Physics | (Cond-Mat.Mes-Hall) 2019-04-08
Mesoscale And Nanoscale Physics
Signature of the Quantized Thermoelectric Hall Effect in a Topological Weyl Semimetal (1904.03179v1)
Fei Han, Nina Andrejevic, Thanh Nguyen, Brian Skinner, Quynh Nguyen, Zhiwei Ding, Ricardo Pablo-Pedro, Shreya Parjan, Vladyslav Kozii, Ahmet Alatas, Ercan Alp, Songxue Chi, Jaime Fernandez-Baca, Shengxi Huang, Liang Fu, Mingda Li
2019-04-05
Thermoelectrics are promising by directly generating electricity from waste heat. However, (sub-) room-temperature thermoelectrics has posed a long-standing challenge, due to the entropic nature of thermopower that is supressed at low temperature. In this light, topological materials offer a new avenue for energy harvest applications. Recent theories predicted that topological Weyl semimetals (WSMs) near quantum limit can lead to a non-saturating longitudinal thermopower, as well as a quantized thermoelectric Hall coefficient approaching to a universal value. Here, we experimentally demonstrate the non-saturating thermopower and the signature of quantized thermoelectric Hall coefficients in WSM tantalum phosphide (TaP). An ultrahigh longitudinal thermopower Sxx = 1.1x10^3 muV/K, along with a power factor ~300 muW/cm/K^2 , are observed ~50K. Moreover, the thermoelectric Hall coefficients develop a plateau at high-fields and low temperatures, which further collapse into a single curve determined by universal constants. Our work highlights the unique electronic structure and topological protection of Weyl nodes toward thermoelectric harvest applications at low temperature.
Two- and three-electron bubbles in Al
Ga
As/Al
Ga
As quantum wells (1904.03159v1)
X. Fu, Q. Shi, M. A. Zudov, G. C. Gardner, J. D. Watson, M. J. Manfra
2019-04-05
We report on transport signatures of eight distinct bubble phases in the
Landau level of a Al
. These phases occur near partial filling factors
and
and have
and
electrons (holes) per bubble, respectively. We speculate that a small amount of alloy disorder in our sample helps to distinguish these broken symmetry states in low-temperature transport measurements.
Quantum Hall stripes in high-density GaAs/AlGaAs quantum wells (1904.03151v1)
X. Fu, Q. Shi, M. A. Zudov, Y. J. Chung, K. W. Baldwin, L. N. Pfeiffer, K. W. West
2019-04-05
We report on quantum Hall stripes (QHSs) formed in higher Landau levels of GaAs/AlGaAs quantum wells with high carrier density (
cm
) which is expected to favor QHS orientation along unconventional
crystal axis and along the in-plane magnetic field
. Surprisingly, we find that at
QHSs in our samples are aligned along
direction and can be reoriented only perpendicular to
Effect of illumination on quantum lifetime in GaAs quantum wells (1904.03146v1)
X. Fu, A. Riedl, M. Borisov, M. A. Zudov, J. D. Watson, G. Gardner, M. J. Manfra, K. W. Baldwin, L. N. Pfeiffer, K. W. West
2019-04-05
Low-temperature illumination of a two-dimensional electron gas in GaAs quantum wells is known to greatly improve the quality of high-field magnetotransport. The improvement is known to occur even when the carrier density and mobility remain unchanged, but what exactly causes it remains unclear. Here, we investigate the effect of illumination on microwave photoresistance in low magnetic fields. We find that the amplitude of microwave-induced resistance oscillations grows dramatically after illumination. Dingle analysis reveals that this growth reflects a substantial increase in the single-particle (quantum) lifetime, which likely originates from the light-induced redistribution of charge enhancing the screening capability of the doping layers.
Circuit-Model Analysis for Spintronic Devices with Chiral Molecules as Spin Injectors (1904.03142v1)
Xu Yang, Tom Bosma, Bart J. van Wees, Caspar H. van der Wal
2019-04-05
Recent research discovered that charge transfer processes in chiral molecules can be spin selective and named the effect Chiral-Induced Spin Selectivity (CISS). Follow-up work studied hybrid spintronic devices with conventional electronic materials and chiral (bio)molecules. However, a theoretical foundation for the CISS effect is still in development and the spintronic signals were not evaluated quantitatively. We present a circuit-model approach that can provide this quantitative evaluation. Our analysis assumes the scheme of a recent experiment that used photosystem~I as spin injectors. We find that the CISS effect can indeed give signals that are strong enough for detection, but also that the observed signals are two orders of magnitude higher than what the CISS effect can provide, indicating that in practice other phenomena can dominate the signals. Our approach provides a generic framework for analyzing this type of experiments and advancing the understanding of the CISS effect.
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