共查询到20条相似文献,搜索用时 31 毫秒
1.
Miao Feng Ohlberg Douglas A. A. Stanley Williams R. Lau Chun Ning 《Applied Physics A: Materials Science & Processing》2011,102(4):943-948
Nanoscale switches will play a crucial role in the design of future nanoelectronic circuits. An interesting candidate involves
metal/molecule/metal structures that operate via modulation of nanoscale conducting channels. When the conductance falls in
the ballistic regime between 1∼2G
Q
(where G
Q
=2e
2/h or ≈80 μS), resonant electron transport was observed in such devices at room temperature. By performing pressure-modulated
conductance microscopy, we have characterized the quantum conducting channels in terms of the wave vector of the electrons.
We also observed two-level fluctuations in conductance, with each level showing opposite pressure responses, confirming the
existence of resonant electron transport. These observations could lead to a new type of high speed quantum switching device
based on electron wave interference. 相似文献
2.
《Superlattices and Microstructures》1999,25(5-6):733-743
The thermopower of Andreev interferometers, which are doubly connected loops in which one arm is a superconductor and one arm is a normal metal, oscillates as a function of magnetic field with a fundamental period corresponding to a flux quantum h / 2 e through the area of the loop. While the magnetoresistance of an Andreev interferometer is symmetric with respect to the magnetic field, the thermopower can be either symmetric or antisymmetric, depending on the topology of the sample. The temperature dependence of the thermopower oscillations is nonmonotonic. This nonmonotonic behavior does not appear to be related to the reentrance observed by many groups in the conductance of normal-metal/superconductor (NS) structures. 相似文献
3.
In this paper, the superconducting order parameter and the energy spectrum of the Bogoliubov excitations are obtained from the Bogoliubov-de Gennes equation for a ferromagnetic superconductor (FS). In the framework of the Blonder-Tinkham-Klapwijk model, we present the differential conductance of the normal metal/insulator/FS junctions. It is shown that the exchange energy h in the FS can lead to the Zeeman splitting of the conductance peaks and the energy difference between the two splitting peaks is equal to 2h. The observation of such Zeeman splitting in the conductance spectrum can be taken as evidence for the coexistence between superconductivity and ferromagnetism. 相似文献
4.
《Current Applied Physics》2020,20(3):451-455
Van der Waals layered transition metal dichalcogenides (TMDCs), as atomically flat two-dimensional materials, have been studied extensively in both fundamental science and application fields in recent years. The reduced-dimensional properties of TMDCs not only provide a route for the fabricating of efficient field effect transistors and optoelectronic devices but also suggest the possibility of the devices that utilize quantum coherency. In this work, we characterize the electron transport properties of ReS2, one of the TMDCs, at both room temperature and low temperature. Of particular note, we measured strong quantum conductance oscillations as a function of the gate voltages and source-drain voltages at reduced temperature, which is evidence of quantum coherent transport. This work unambiguously establishes ReS2 as a promising candidate for future quantum materials. 相似文献
5.
6.
Conductance in monatomic metal contacts is quantized; it increases in discrete steps of one conductance quantum 2e(2)/h. By contrast, in a vacuum barrier between two metal surfaces we find that conductance increases linearly and continuously with the interaction energy between individual atoms. This behavior shows unambiguously that current flow between single atoms is a measure for their chemical interaction. In the controlled environment of a scanning tunneling microscope it should allow us to study the formation of covalent bonds up to the point where these atoms finally jump into contact. 相似文献
7.
The influence of the quantum size effect (QSE) in very thin Pd and Au films (0.5<d<10 [nm]) deposited on glass tips is studied by means of field emission at various anode potentials. The thickness-dependent
field emission current characteristics show short periodic variations with a period of about 0.3 nm for both Pd and Au. The
measured QSE oscillations and their amplitudes differ strongly from those expected qualitatively from model calculations for
the smallest thicknesses. A model for the metal film based on a modification of the uniform background model is presented,
and the thickness dependence of the conductance and the field emission current density are qualitatively discussed. Possible
explanations of some discrepancies between calculations and the measured field emission current characteristics are proposed. 相似文献
8.
V. T. Petrashov R. Sh. Shaikhaidarov I. A. Sosnin 《Czechoslovak Journal of Physics》1996,46(Z4):2327-2328
We report measurements of the temperature dependence of the amplitude of phase-periodic conductance oscillations in disordered
normal metal (Ag) structures, attached to a superconducting (Al) wire at two points. The amplitude of oscillations reaches
its maximum at temperatureT
*, when the Thouless energy is of the order ofk
B
T. The results are in agreement with recent calculations by Nazarov and Stoof [Phys. Rev. Lett. 76 (1996) 823]. 相似文献
9.
Differential conductance in normal-metal/insulator/metal/d-wave superconductor junction carrying a supercurrent 下载免费PDF全文
This paper applies the Bogoliubov--de Gennes equation and
the Blonder--Tinkham--Klapwijk approach to study the oscillatory
behaviour of differential conductance in a normal metal/insulator/metal/d-wave
superconductor junction carrying a
supercurrent Is. We find that (i) a three-humped structure
appears at a nearly critical supercurrent Is and z ≈
0.5 for the normal metal/insulator/metal/d_x2 + y2-wave
superconductor junction; (ii) the zero-bias conductance peak splits
into two peaks with sufficiently large applied current for the normal
metal/insulator/metal/dxy-wave superconductor junction; (iii)
the conductance spectrum exhibits oscillating behaviour with the
bias voltage and the peaks of the resonances are suppressed by
increasing supercurrent Is. 相似文献
10.
L. P. Kouwenhoven N. C. van der Vaart A. T. Johnson W. Kool C. J. P. M. Harmans J. G. Williamson A. A. M. Staring C. T. Foxon 《Zeitschrift für Physik B Condensed Matter》1991,85(3):367-373
We have studied charging effects in a lateral split-gate quantum dot defined by metal gates in the two dimensional electron gas (2 DEG) of a GaAs/AlGaAs heterostructure. The gate structure allows an independent control of the conductances of the two tunnel barriers separating the quantum dot from the two 2 DEG leads, and enables us to vary the number of electrons that are localized in the dot. We have measured Coulomb oscillations in the conductance and the Coulomb staircase in current-voltage characteristics and studied their dependence on the conductances of the tunnel barriers. We show experimentally that at zero magnetic field charging effects start to affect the transport properties when both barrier conductances are smaller than the first quantized conductance value of a point contact at 2e
2/h. The experiments are described by a simple model in terms of electrochemical potentials, which includes both the discreteness of the electron charge and the quantum energy states due to confinement. 相似文献
11.
Y. Zhang M. Han 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(2):277-282
Using the π orbital tight-binding model and the
multi-channel Laudauer-Büttiker formula, the combined effect of
Aharonov-Bohm effect (induced by an axial magnetic field) and uniaxial
strain on quantum conductance oscillations of the electronic Fabry-Perot
resonators composed of armchair and metallic zigzag single-walled carbon
nanotubes (SWNTs) has been studied. It is found that, for the case of the
armchair SWNT, conductance oscillations near the band gap are dominated by
Aharonov-Bohm effect, while the conductance oscillations in other regions
are dominated by the uniaxial strains. The combined effect of Aharonov-Bohm
effect and uniaxial strains on quantum conductance oscillations is not
obvious. But, for the case of the metallic zigzag SWNTs, obvious
single-channel transport and one or two conductance oscillations existing in
two different gate voltage ranges were found by the combined effect of
uniaxial strain and axial magnetic field. 相似文献
12.
利用非平衡格林函数方法, 理论研究T型双量子点分子Aharonov-Bohm (A-B)干涉仪的电荷及其自旋输运性质. 通过控制T型双量子点分子内量子点间有无耦合, 能够实现在同一电子能级位置处分别出现共振和反共振状态, 根据此性质, 能将体系设计成量子开关器件. 当将两个完全相同的T型双量子点分子分别嵌入A-B干涉仪两臂中时, 磁通取适当数值, 能够出现完全的量子相消干涉. 通过调节量子点能级、左右两电极间的偏压和Rashba自旋轨道相互作用强度, 可对体系自旋流进行调控.
关键词:
非平衡格林函数
T型双量子点分子
Aharonov-Bohm干涉仪
自旋输运 相似文献
13.
H. Yokoyama T. Sato K. Ono Y. Hirayama S. Tarucha 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):527
Combined quantum wire and quantum dot system is theoretically predicted to show unique conductance properties associated with Coulomb interactions. We use a split gate technique to fabricate a quantum wire containing a quantum dot with two tunable potential barriers in a two-dimensional electron gas. We observe the effects of the quantum dot cavity on the electron transport through the quantum wire, such as Coulomb oscillations near the pinch-off voltage and periodic conductance oscillations on the first conductance plateau. 相似文献
14.
Coherent charge transport in ferromagnet/semiconductor nanowire/ferromagnet double barrier junctions with the interplay of Rashba spin-orbit coupling,induced superconducting pair potential,and external magnetic field 下载免费PDF全文
《中国物理 B》2017,(7)
By solving the Bogoliubov-de Gennes equation, the influence of the interplay of Rashba spin-orbit coupling, induced superconducting pair potential, and external magnetic field on the spin-polarized coherent charge transport in ferromagnet/semiconductor nanowire/ferromagnet double barrier junctions is investigated based on the Blonder-Tinkham-Klapwijk theory. The coherence effect is characterized by the strong oscillations of the charge conductance as a function of the bias voltage or the thickness of the semiconductor nanowire, resulting from the quantum interference of incoming and outgoing quasiparticles in the nanowire. Such oscillations can be effectively modulated by varying the strength of the Rashba spin-orbit coupling, the thickness of the nanowire, or the strength of the external magnetic field. It is also shown that two different types of zero-bias conductance peaks may occur under some particular conditions, which have some different characteristics and may be due to different mechanisms. 相似文献
15.
Natalya A. Zimbovskaya 《Solid State Communications》2006,138(12):559-562
In the present work, we theoretically analyze the effect of the Fermi surface local geometry on quantum oscillations in the velocity of an acoustic wave travelling in metal across a strong magnetic field. We show that local flattenings of the Fermi surface could cause significant amplification of quantum oscillations. This occurs due to enhancement of commensurability oscillations modulating the quantum oscillations in the electron density of states on the Fermi surface. The amplification in the quantum oscillations could be revealed at fitting directions of the magnetic field. 相似文献
16.
Coulomb blockade oscillations are found in the electron thermal conductance of a quantum dot (nanocrystal) in the regime of weak coupling with two electrode leads that is calculated within a linear response theory. An analytical expression is obtained in the quantum limit where electron level spacing is non-negligible. The effect of confinement on the electron thermal conductance is thereby explicitly shown. It is shown that in the quantum limit the periodicity of the Coulomb-blockade oscillations of the electron thermal conductance is the same as of the conductance. The shape and the magnitude of the electron thermal conductance depend explicitly on the temperature and the energy level spacing. It is found that the electron thermal conductance decreases nearly exponentially with increasing confinement and decreasing temperature. 相似文献
17.
We present theoretical calculations and experimental measurements which reveal finite-size effects in the tunneling between two parallel quantum wires, fabricated at the cleaved edge of a GaAs/AlGaAs bilayer heterostructure. Observed oscillations in the differential conductance, as a function of bias voltage and applied magnetic field, provide direct information on the shape of the confining potential. Superimposed modulations indicate the existence of two distinct excitation velocities, as expected from spin-charge separation. 相似文献
18.
19.
We show that multiple point contacts on a barrier separating two laterally coupled quantum Hall fluids induce Aharonov-Bohm (AB) oscillations in the tunneling conductance. These quantum coherence effects provide new evidence for the Luttinger liquid behavior of the edge states of quantum Hall fluids. For a two point contact, we identify coherent and incoherent regimes determined by the relative magnitude of their separation and the temperature. We analyze both regimes in the strong and weak tunneling amplitude limits as well as their temperature dependence. We find that the tunneling conductance should exhibit AB oscillations in the coherent regime, both at strong and weak tunneling amplitudes with the same period but with different functional form. 相似文献
20.
K.M Leung 《Solid State Communications》1984,50(5):449-452
A quantum mechanical calculation of the differential elastic scattering cross-section of light from a metal microparticle is presented. The scattering intensity is found to exhibit oscillations as a function of the frequency due to the discreteness of the electron energy levels. The magnitudes of the oscillations have a sensitive dependence on the size of the electron mean free path relative to the diameter of the particle. 相似文献