共查询到20条相似文献,搜索用时 546 毫秒
1.
《Superlattices and Microstructures》1999,25(5-6):1041-1053
In tunneling spectroscopy of superconductors the density of states close to the surface or the interface to an insulating tunneling barrier is probed. For d-wave superconductors the particle–hole coherence results in interesting new phenomena at surfaces such as the formation of bound surface states at the Fermi level by Andreev reflection due to a sign change of the order parameter field in different k -directions. The probing of these states represents a phase-sensitive experiment allowing the determination of the order parameter symmetry in superconductors. We summarize the present experimental status with respect to the study of high-temperature superconductors (HTS). We discuss theoretically predicted consequences of a dominating d-wave order parameter in the hole-doped HTS on their tunneling spectra as well as on the physics of high-temperature superconductor Josephson junctions. A comparison of the tunneling spectra obtained for hole- and electron-doped HTS leads to the conclusion that the former have a d-wave, whereas the latter most likely have an anisotropic s-wave order parameter. We also address some unsettled questions related to the presence of a state with broken time-reversal symmetry at surfaces and interfaces of d-wave HTS and discuss specific features of d-wave tunnel junctions that have been predicted theoretically but still not been confirmed in experiments. 相似文献
2.
The inelastic-tunneling model can be used to explain the linear conductance background observed in tunneling in the high-Tc oxide super conductors. Introducing a parameter into the tunneling Hamiltanian to describe the strength of on-site Coulomb repulsion, we have derived an expression for the inelastic-tunneling conductance. We further discuss what form of the spin-fluctuation propagators in the inelastic-tunneling model can produce the linear tunneling conductance which would agree well with the experimental data. 相似文献
3.
Frank Grossmann Thomas Dittrich Peter Jung Peter Hänggi 《Journal of statistical physics》1993,70(1-2):229-245
The quantum dynamics of a quartic double well, subjected to a harmonically oscillating field, is studied in the framework of the Floquet formalism. The modifications of the familiar tunneling process due to the driving are investigated numerically and explained in terms of the structure of the corresponding local quasienergy spectrum. In particular, there is a one-dimensional manifold in the parameter space spanned by the amplitude and frequency of the driving force, where tunneling is almost completely suppressed by the coherent driving. The quantal dynamics in the semiclassical regime as well as the influence of weak incoherent processes are briefly discussed. 相似文献
4.
Casey W. Miller 《Journal of magnetism and magnetic materials》2009,321(17):2563-2565
Spin filter tunneling is considered in the low bias limit as functions of the temperature dependent barrier parameters. We demonstrate the generation of spin polarized tunneling currents in relation to the magnetic order parameter, and discuss how an interfacially suppressed order parameter leads to a temperature dependent tunneling current asymmetry. Analyzing the full parameter space reveals that the often overlooked barrier thickness plays a critical role in spin filter tunneling. With all else fixed, thicker barriers yield higher spin polarization, and allow a given polarization to be achieved at higher temperatures. This insight may open the door for new materials to serve as spin filter barriers. 相似文献
5.
Sensitivity of the tunneling current to electron energy is calculated in the context of scanning tunneling microscopy for the vacuum case by using an appropriate parameter. In addition, a mathematical relationship between this parameter and the phase associated with the involved Schrödinger wavefunctions is obtained. 相似文献
6.
The inelastic-tunneling model can be used to explain the linear conductance background observed in tun-neling in the high-Tc oxide super conductors. Introducing a parameter into the tunneling Hamiltanian to describe the strength of on-site Coulomb repulsion, we have derived an expression for the inelastic-tunneling conductance. We further discuss what form of the spin-fluctuation propagators in the inelastic-tunneling model can produce the linear tunneling conductance which would agree well with the experimental data. 相似文献
7.
Reiss HR 《Physical review letters》2008,101(4):043002
It is shown that tunneling theories of ionization by lasers are subject to upper and lower bounds on the Keldysh parameter gamma. The tunneling limit, gamma-->0, applies to ionization by quasistatic electric fields, but not by laser fields. For lasers, the gamma-->0 limit requires a relativistic treatment. Bounds on the applicability of tunneling theories depend on parameters other than gamma, confirming the rule that strong-field phenomena require more than one dimensionless parameter for scaling. 相似文献
8.
9.
V. I. Mel''nikov 《Physica A》1985,130(3):606-615
At sufficiently low friction the Fokker-Planck equation for Brownian motion in a potential well is reduced to an integral equation for the energy variable. The basic small parameter of the problem is the ratio of the temperature T to the depth U0 of the well. Quantum tunneling effects are naturally incorporated into the calculations. An explicit solution for Kramers' problem of the lifetime of the Brownian particle in the potential well is given. 相似文献
10.
设计了(CdZnTe,ZnSeTe)/ZnTe复合量子阱结构,并用吸收光谱、室温光致发光谱和飞秒脉冲抽运-探测方法研究了该复合结构中的激子隧穿过程.分别测量了该结构中CdZnTe/ZnTe量子阱层和ZnSeTe/ZnTe量子阱层中激子衰减时间.观察到从CdZnTe/ZnTe量子阱层向ZnSeTe/ZnTe量子阱层的快速激子隧穿,隧穿时间为5.5ps.
关键词:
(CdZnTe
ZnSeTe)/ZnTe复合量子阱
激子
隧穿
抽运-探测 相似文献
11.
P. I. Arseev N. S. Maslova V. N. Mantsevich 《Journal of Experimental and Theoretical Physics》2012,115(1):141-153
We demonstrate that the tunneling current flowing through a system with Coulomb correlations leads to a charge redistribution between the different localized states. A simple model consisting of two electron levels is analyzed by means of the Heisenberg equations of motion taking correlations of electron filling numbers in localized states into account exactly in all orders. We consider various relations between the Coulomb interaction and localized electron energies. Sudden jumps of the electron density at each level in a certain range of the applied bias are found. We find that for some parameter range, inverse occupation in the two-level system appears due to Coulomb correlations. It is also shown that Coulomb correlations lead to the appearance of negative tunneling conductivity at a certain relation between the values of tunneling rates from the two electron levels. 相似文献
12.
Lignier H Sias C Ciampini D Singh Y Zenesini A Morsch O Arimondo E 《Physical review letters》2007,99(22):220403
We report on measurements of dynamical suppression of interwell tunneling of a Bose-Einstein condensate (BEC) in a strongly driven optical lattice. The strong driving is a sinusoidal shaking of the lattice corresponding to a time-varying linear potential, and the tunneling is measured by letting the BEC freely expand in the lattice. The measured tunneling rate is reduced and, for certain values of the shaking parameter, completely suppressed. Our results are in excellent agreement with theoretical predictions. Furthermore, we have verified that, in general, the strong shaking does not destroy the phase coherence of the BEC, opening up the possibility of realizing quantum phase transitions by using the shaking strength as the control parameter. 相似文献
13.
We apply the null-geodesic method to investigate tunneling radiation of charged and magnetized massive particles from Taub-NUT-Reissner-Nordström black holes endowed with electric as well as magnetic charges in Anti-de Sitter (AdS) spaces. The geodesics of charged massive particle tunneling from the black hole is not lightlike, but can be determined by the phase velocity. We find that the tunneling rate is related to the difference of Bekenstein-Hawking entropies of the black hole before and after the emission of particles. The entropy differs from just a quarter area at the horizon of black holes with NUT parameter. The emission spectrum is not precisely thermal anymore and the deviation from the precisely thermal spectrum can bring some information out, which can be treated as an explanation to the information loss paradox. The result can also be treated as a quantum-corrected radiation temperature, which is dependent on the black hole background and the radiation particle’s energy and charges. 相似文献
14.
本文基于量子机制建立了单轴应变硅nMOSFET栅隧穿电流模型,分析了隧穿电流与器件结构参数、偏置电压及应力的关系.仿真分析结果与单轴应变硅nMOSFET的实验结果符合较好,表明该模型可行.同时与具有相同条件的双轴应变硅nMOSFET的实验结果相比,隧穿电流更小,从而表明单轴应变硅器件更具有优势.该模型物理机理明确,不仅适用于单轴应变硅nMOSFET,只要将相关的参数置换,该模型也同样适用于单轴应变硅pMOSFETs.
关键词:
单轴应变
nMOSFET
栅隧穿电流
模型 相似文献
15.
By defining a suitable parameter, the sensitivity to voltage of the current intensity in scanning tunneling microscopy is determined in terms of the tunneling differential electrical conductance and its first derivative. In addition, the value of the above first derivative (which is a relevant merit factor) for maximum sensitivity is obtained. 相似文献
16.
A new class of superconducting molecular intercalation complexes has been discovered in which paramagnetic molecules reside between metallic dichalcogenide layers six Angstroms thick. Interlayer coupling of the order parameter by Josephson tunneling appears unlikely. 相似文献
17.
In the present work, we report the interplay of single particle and Cooper pair tunnelings on the superconducting state of
layered high-T
c cuprate superconductors. For this we have considered a model Hamiltonian incorporating the intra-planar interactions and
the contributions arising due to the coupling between the planes. The interplanar interactions include the single particle
tunneling as well as the Josephson tunneling of Cooper pairs between the two layers. The expression of the out-of-plane correlation
parameter which describes the hopping of a particle from one layer to another layer in the superconducting state is obtained
within a Bardeen-Cooper-Schriefer (BCS) formalism using the Green’s function technique. This correlation is found to be sensitive
to the various parameter of the model Hamiltonian. We have calculated the out-of-plane contribution to the superconducting
condensation energy. The calculated values of condensation energy are in agreement with those obtained from the specific heat
and the c-axis penetration depth measurements on bilayer cuprates. 相似文献
18.
Godfrey Gumbs 《Solid State Communications》2003,128(12):443-448
A model calculation is reported for the tunneling probability of one as well as two interacting electrons from a quantum well within a narrow channel. We discuss the cases when the two electrons are spin polarized or unpolarized by transforming the system to a noninteracting one with the use of quantal density functional theory to obtain an effective single-particle confining potential. A semiclassical approach is used to obtain the tunneling probability from this effective potential. The calculation is motivated by recent measurements of the conductance of an electron gas in a narrow channel but is not meant to explain the anomalous behavior that has been reported since, for example, we deal with a simplified two-level system. Numerical results for the tunneling probability are presented. 相似文献
19.
Danfu Liang Jiawei Zhang Xili Zhang 《International Journal of Theoretical Physics》2018,57(8):2437-2446
We investigate the quantum transport of a single particle trapped in a tilted optical lattice modulated with periodical delta kicks, and attempt to figure out the relationship between chaos and delocalization or quantum tunneling. We illustrate some resonant parameter lines existing in both chaotic and regular parameter regions, and discover the velocity of delocalization of particle tends to faster in the resonant line as well as the lines in which the lattice tilt is an integral multiple n of tilt driving frequency in chaotic region. While the degree of localization is linked to the distance between parameter points and resonant lines. Those useful results can be experimentally applied to control chaos-assisted transport of single particle held in optical lattices. 相似文献
20.
We present a comparative study on the acoustic tunneling through artificial periodical composites, from phononic crystals to acoustic metamaterials. We find that the features of the acoustic tunneling are closely related with the origins of band gaps. In particular, the band gap associated with the negative effective material parameter in the metamaterial results in a better analog of the tunneling effect to the quantum system. 相似文献