共查询到20条相似文献,搜索用时 468 毫秒
1.
N. Goel J. Graham J.C. Keay K. Suzuki S. Miyashita M.B. Santos Y. Hirayama 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):455
Two different device geometries are fabricated to investigate ballistic transport of electrons in low-dimensional InSb structures. Negative bend resistance is observed in four-terminal devices of channel widths ranging from 0.2 to 0.65 μm. We also report the observation of conductance quantization in quantum point contacts fabricated using in-plane gates. The one-dimensional subbands depopulate with increasing transverse magnetic field up to 3 T. Zeeman splitting is resolved at magnetic fields above 0.9 T. 相似文献
2.
N. Goel S. J. Chung M. B. Santos K. Suzuki S. Miyashita Y. Hirayama 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):251
Measurements were made on a 0.2 μm four-terminal device, fabricated from an InSb/Al0.15In0.85Sb quantum well structure, at temperatures from 1.5 to 300 K. Negative bend resistance, a signature of ballistic transport, was observed at temperatures up to 205 K. The disappearance of the negative bend resistance at higher temperatures was accompanied by a non-linear dependence of the Hall voltage on magnetic field. The non-linearity indicates multiple-carrier conduction, which we characterize using quantitative mobility spectrum analysis. 相似文献
3.
We study multiband semiconducting nanowires proximity-coupled with an s-wave superconductor. We show that, when an odd number of subbands are occupied, the system realizes a nontrivial topological state supporting Majorana modes. We study the topological quantum phase transition in this system and calculate the phase diagram as a function of the chemical potential and magnetic field. Our key finding is that multiband occupancy not only lifts the stringent constraint of one-dimensionality but also allows one to have higher carrier density in the nanowire, and as such multisubband nanowires are better suited for observing the Majorana particle. We study the robustness of the topological phase by including the effects of the short- and long-range disorder. We show that there is an optimal regime in the phase diagram ("sweet spot") where the topological state is to a large extent insensitive to the presence of disorder. 相似文献
4.
Interplay of spin–orbit coupling and superconducting correlations in germanium telluride thin films 下载免费PDF全文
Vijay Narayan Thuy‐Anh Nguyen Rhodri Mansell David Ritchie Gregor Mussler 《固体物理学:研究快报》2016,10(3):253-259
There is much current interest in combining superconductivity and spin–orbit coupling in order to induce the topological superconductor phase and associated Majorana‐like quasiparticles which hold great promise towards fault‐tolerant quantum computing. Experimentally these effects have been combined by the proximity‐coupling of super‐conducting leads and high spin–orbit materials such as InSb and InAs, or by controlled Cu‐doping of topological insu‐lators such as Bi2Se3. However, for practical purposes, a single‐phase material which intrinsically displays both these effects is highly desirable. Here we demonstrate coexisting superconducting correlations and spin–orbit coupling in molecular‐beam‐epitaxy‐grown thin films of GeTe. The former is evidenced by a precipitous low‐temperature drop in the electrical resistivity which is quelled by a magnetic field, and the latter manifests as a weak antilocalisation (WAL) cusp in the magnetotransport. Our studies reveal several other intriguing features such as the presence of two‐dimensional rather than bulk transport channels below 2 K, possible signatures of topological superconductivity, and unexpected hysteresis in the magnetotransport. Our work demonstrates GeTe to be a potential host of topological SC and Majorana‐like excitations, and to be a versatile platform to develop quantum information device architectures. (© 2016 The Authors. Phys. Status Solidi RRL published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
The last several years have witnessed the rapid developments in the study and understanding of topological insulators. In this review, after a brief summary of the history of topological insulators, we focus on the recent progress made in transport experiments on topological insulator films and nanowires. Some quantum phenomena, including the weak antilocalization, the Aharonov-Bobm effect, and the Shubnikov-de Haas oscillations, observed in these nanostructures are described. In addition, the electronic transport evidence of the superconducting proximity effect as well as an anomalous resistance enhancement in topological insulator/superconductor hybrid structures is included. 相似文献
6.
The exploitation of the spin in charge-based systems is opening revolutionary opportunities for device architecture. Surprisingly, room temperature electrical transport through magnetic nanowires is still an unresolved issue. Here, we show that ferromagnetic (Co) suspended atom chains spontaneously display an electron transport of half a conductance quantum, as expected for a fully polarized conduction channel. Similar behavior has been observed for Pd (a quasimagnetic 4d metal) and Pt (a nonmagnetic 5d metal). These results suggest that the nanowire low dimensionality reinforces or induces magnetic behavior, lifting off spin degeneracy even at room temperature and zero external magnetic field. 相似文献
7.
We experimentally investigate transport properties of a single planar junction between the niobium superconductor and the edge of a two-dimensional electron system in a narrow In0.75Ga0.25As quantum well with strong Rashba-type spin-orbit coupling. We experimentally demonstrate suppression of Andreev reflection at low biases at ultralow temperatures. From the analysis of temperature and magnetic field behavior, we interpret the observed suppression as a result of a spin-orbit coupling. There is also an experimental sign of the topological superconductivity realization in the present structure. 相似文献
8.
We study mesoscopic spin Hall effect on the surface of a topological insulator with a step-function potential by using the McMillan method commonly used in the study of superconductor junctions. In the ballistic transport regime, we predict a giant spin polarization induced by a transverse electric current with parameter suitable to the topological insulator thin film Bi(2)Se(3). The spin polarization oscillates across the potential boundary with no confinement due to the Klein paradox, and should be observable in a spin resolved scanning tunneling microscope. 相似文献
9.
We discuss the Luttinger liquid behaviour of a semiconducting
quantum wire. We show that the measured value of the bulk
critical exponent, αbulk, for the tunneling density of
states can be easily calculated.
Then, the problem of the transport through a quantum dot formed
by two quantum point contacts along the quantum wire, weakly
coupled to spinless Tomonaga-Luttinger liquids is studied,
including the action of a strong transverse magnetic field B.
The known magnetic dependent peaks of the
conductance, G(B), in the ballistic regime at a very low
temperature, T, have to be reflected also in the transport at
higher T and in different regimes. The temperature dependence of
the maximum Gmax of the conductance peak, according to the
Correlated Sequential Tunneling theory, yields the power law
Gmax∝T2α end-1, with the critical exponent,
αend, strongly reduced by B.
This behaviour suggests the use of a similar device as a magnetic
field modulated transistor. 相似文献
10.
Weak antilocalization and interaction-induced localization of Dirac and Weyl Fermions in topological insulators and semimetals 下载免费PDF全文
Weak localization and antilocalization are quantum transport phenomena that arise from the quantum interference in disordered metals.At low temperatures,they can give distinct temperature and magnetic field dependences in conductivity,allowing the symmetry of the system to be explored.In the past few years,they have also been observed in newly emergent topological materials,including topological insulators and topological semimetals.In contrast from the conventional electrons,in these new materials the quasiparticles are described as Dirac or Weyl fermions.In this article,we review our recent efforts on the theories of weak antilocalization and interaction-induced localization for Dirac and Weyl fermions in topological insulators and topological semimetals. 相似文献
11.
The new class of phenomena described in this review is based on the interaction between spatially separated, but closely located ferromagnets and superconductors, the so-called ferromagnet–superconductor hybrids (FSH). Typical FSH are: coupled uniform and textured ferromagnetic and superconducting films, magnetic dots over a superconducting film, magnetic nanowires in a superconducting matrix, etc. The interaction is provided by the magnetic field generated by magnetic textures and supercurrents. The magnetic flux from magnetic structures or topological defects can pin vortices or create them, changing the transport properties and transition temperature of the superconductor. On the other hand, the magnetic field from supercurrents (vortices) strongly interacts with the magnetic subsystem, leading to formation of coupled magnetic–superconducting topological defects. The proximity of ferromagnetic layer dramatically changes the properties of the superconducting film. The exchange field in ferromagnets not only suppresses the Cooper-pair wavefunction, but also leads to its oscillations, which in turn leads to oscillations of observable values: the transition temperature and Josephson current. In particular, in the ground state of the Josephson junction the relative phase of two superconductors separated by a layer of ferromagnetic metal is equal to?π?instead of the usual zero (the so-called π-junction). Such a junction carries a spontaneous supercurrent and possesses other unusual properties. Theory predicts that rotation of magnetization transforms s-pairing into p-pairing. The latter is not suppressed by the exchange field and serves as a carrier of long-range interaction between superconductors. 相似文献
12.
After showing that the electron wavelength and electron drift-mobility are quantized in quantum quasi-one-dimensional electron wave guides, we introduce and determine electron wavelength and electron drift-mobility quantum operators for investigating electron transport through the above waveguides in the ballistic regime. A linear relationship between the two aforementioned operators is found. Our formulation is valid for carbon nanotubes and nanowires. 相似文献
13.
A direct signature of electron transport at the metallic surface of a topological insulator is the Aharonov-Bohm oscillation observed in a recent study of Bi2Se3 nanowires [Peng, Nature Mater. 9, 225 (2010)] where conductance was found to oscillate as a function of magnetic flux ? through the wire, with a period of one flux quantum ?0=h/e and maximum conductance at zero flux. This seemingly agrees neither with diffusive theory, which would predict a period of half a flux quantum, nor with ballistic theory, which in the simplest form predicts a period of ?0 but a minimum at zero flux due to a nontrivial Berry phase in topological insulators. We show how h/e and h/2e flux oscillations of the conductance depend on doping and disorder strength, provide a possible explanation for the experiments, and discuss further experiments that could verify the theory. 相似文献
14.
The behavior of an acoustoelectric current through a three-dimensional quantum microconstriction placed in a longitudinal uniform magnetic field is studied theoretically in the ballistic transport regime. The oscillation periods of the acoustoelectric current are studied in detail as functions of the chemical potential and the magnetic field induction. The temperature effect is taken into account. It is shown that the acoustoelectric current as a function of the chemical potential can exhibit a steplike behavior. The limits for the existence of a steplike structure are determined. 相似文献
15.
Nadj-Perge S Pribiag VS van den Berg JW Zuo K Plissard SR Bakkers EP Frolov SM Kouwenhoven LP 《Physical review letters》2012,108(16):166801
A double quantum dot in the few-electron regime is achieved using local gating in an InSb nanowire. The spectrum of two-electron eigenstates is investigated using electric dipole spin resonance. Singlet-triplet level repulsion caused by spin-orbit interaction is observed. The size and the anisotropy of singlet-triplet repulsion are used to determine the magnitude and the orientation of the spin-orbit effective field in an InSb nanowire double dot. The obtained results are confirmed using spin blockade leakage current anisotropy and transport spectroscopy of individual quantum dots. 相似文献
16.
We investigate the magnetotransport in large area graphene Hall bars epitaxially grown on silicon carbide. In the intermediate field regime between weak localization and Landau quantization, the observed temperature-dependent parabolic magnetoresistivity is a manifestation of the electron-electron interaction. We can consistently describe the data with a model for diffusive (magneto)transport that also includes magnetic-field-dependent effects originating from ballistic time scales. We find an excellent agreement between the experimentally observed temperature dependence of magnetoresistivity and the theory of electron-electron interaction in the diffusive regime. We can further assign a temperature-driven crossover to the reduction of the multiplet modes contributing to electron-electron interaction from 7 to 3 due to intervalley scattering. In addition, we find a temperature-independent ballistic contribution to the magnetoresistivity in classically strong magnetic fields. 相似文献
17.
作为马约拉纳费米子的“凝聚态版本”,马约拉纳零能模是当前凝聚态物理领域的研究热点.马约拉纳零能模满足非阿贝尔统计,可以构建受拓扑保护的量子比特.这种由空间上分离的马约拉纳零能模构建的拓扑量子比特不易受局域噪声的干扰,具有长的退相干时间,在容错量子计算中具有重要的应用前景.半导体/超导体纳米线是研究马约拉纳零能模和拓扑量子计算的理想实验平台.本文综述了高质量半导体纳米线外延生长、半导体/超导体异质结制备以及相应的马约拉纳零能模研究方面的进展,并对半导体/超导体纳米线在量子计算中的应用前景进行了展望. 相似文献
18.
Z. D. Kvon K.-M. Dantscher M.-T. Scherr A. S. Yaroshevich N. N. Mikhailov 《JETP Letters》2016,104(10):716-720
The terahertz resistive response of a two-dimensional topological insulator in a HgTe quantum well in the quasiballistic transport regime is studied. The photoresistance appearing only near the charge neutrality point is detected. The application of the magnetic field up to 4 T in the plane of the quantum well results in an increase in the photoresistance in the peak and in the expansion of the region near the charge neutrality point where it exists. The reported results imply that the observed photoresistance is due to transitions involving edge dispersion branches of the two-dimensional topological insulator. 相似文献
19.
20.
The thermodynamic properties of an In Sb quantum dot have been investigated in the presence of Rashba spin–orbit interaction and a static magnetic field. The energy spectrum and wave-functions for the system are obtained by solving the Schrodinger wave-equation analytically. These energy levels are employed to calculate the specific heat, entropy,magnetization and susceptibility of the quantum dot system using canonical formalism. It is observed that the system is susceptible to maximum heat absorption at a particular value of magnetic field which depends on the Rashba coupling parameter as well as the temperature. The variation of specific heat shows a Schottky-like anomaly in the low temperature limit and rapidly converges to the value of 2kB with the further increase in temperature. The entropy of the quantum dot is found to be inversely proportional to the magnetic field but has a direct variation with temperature. The substantial effect of Rashba spin–orbit interaction on the magnetic properties of quantum dot is observed at low values of magnetic field and temperature. 相似文献