We experimentally explore the phenomenon of electron tunneling across a modulated tunneling barrier which is created between an STM tip and an Au film deposited on a vibrating piezo surface. Measurements of the time series of the quantum mechanical tunneling current across the modulating barrier show large fluctuations. Analysis of the average work done in establishing tunneling current in finite time interval shows a distribution of both positive and negative work events. The negative work events suggest tunneling against the bias voltage direction. We show that these distributions obey the Gallavotti Cohen Non-equilibrium Fluctuation Relations (GC-NEFR) valid for systems driven through a dissipating environment. Typically, while the GC-NEFR has been shown for non -equilibrium classical systems we show its validity for the quantum mechanical tunneling process too. The GC-NEFR analysis also gives us a way to measure the dissipation present in this quantum tunneling system. We propose the modulated barrier behaves like a lossy scattering medium for the tunneling electrons resulting in a tendency to randomize of the tunneling process.
In this talk I present a summary of recent work on tunnel junctions of a fractional quantum Hall fluid and an electron reservoir, a Fermi liquid. I consider first the case of a single point contact. This is a an exactly solvable problem from which much can be learned. I also discuss in some detail how these solvable junction problems can be used to understand many aspects of the recent electron tunneling experiments into edge states. I also give a detailed picture of the unusual behavior of these junctions in their strong coupling regime. A pedagogical introduction to the theories of edge stat…
The variety of nanowire crystal structures gave rise to unique and novel transport phenomena. In particular, we have explored the superlattice profile generated by strain field modulation in twinplane nanowires for the tuning of transport channels and the built-in spin-orbit potential profile of polytypic nanowires, in order to realize a spin filter. The Multicomponent Scattering Approach has been used in terms of the Transfer Matrix Method to describe the phase-time of charge carriers. This system showed advantages for attaining conditions for the propagation of wave packets with negative gro…
We study tunneling between period two states of a parametrically modulated oscillator. The tunneling matrix element is shown to oscillate with the varying frequency of the modulating field. The effect is due to spatial oscillations of the wave function and the related interference in the classically forbidden region. The oscillations emerge already in the ground state of the oscillator Hamiltonian in the rotating frame, which is quartic in the momentum.
We develop analytical models of optical-field electron tunneling from the edge and surface of two-dimensional (2D) materials, including the effects of reduced dimensionality, non-parabolic energy dispersion, band anisotropy, quasi-time dependent tunneling and emission dynamics indueced by the laser field. We discover a universal scaling between the tunneling current density $J$ and the laser electric field $F$: In($J/|F|^β)\propto1/|F|$ with $β= 3 / 2$ in the edge emission and $β= 1$ in the vertical surface emission, which both are distinctive from the traditional Fowler-Nordheim (FN) model of…
We study a gated quantum wire contacted to source and drain electrodes in the Fabry-Perot regime. The wire is also coupled to a third terminal (tip), and we allow for an asymmetry of the tip tunneling amplitudes of right and left moving electrons. We analyze configurations where the tip acts as an electron injector or as a voltage-probe, and show that the transport properties of this three-terminal set-up exhibit very rich physical behavior. For a non-interacting wire we find that a tip in the voltage-probe configuration affects the source-drain transport in different ways, namely by suppressi…
The electromagnetic characteristics of bilayer quantum Hall systems in the presence of interlayer coherence and tunneling are studied by means of a pseudospin-texture effective theory and an algebraic framework of the single-mode approximation, with emphasis on clarifying the nature of the low-lying neutral collective mode responsible for interlayer tunneling phenomena. A long-wavelength effective theory, consisting of the collective mode as well as the cyclotron modes, is constructed. It is seen explicitly from the electromagnetic response that gauge invariance is kept exact, this implying, i…
The band structure and transport properties of massive Dirac Fermions in bilayer graphene with velocity modulation in space are investigated in presence of the previously created band gap. It is pointed out that the velocity engineering is considered as a factor to control the band gap of symmetry-broken bilayer graphene. The band gap is direct and independent of velocity value if velocity modulated in two layers is set up equally. Otherwise, in the case of interlayer asymmetric velocity, not only the band gap is indirect, but also the electron-hole symmetry fails. This band gap is controllabl…
Electric-Field Control of Quantum Tunneling Regimes in Focused He-Ion-Beam-Irradiated Oxide Interfaces
CNR-SPIN（意大利国家研究委员会自旋物理学研究所）；University of Naples Federico II（那不勒斯费德里科二世大学）；Physikalisches Institut, Center for Quantum Science (CQ) and LISA+, University of Tübingen（蒂宾根大学物理学院量子科学中心与LISA+）；Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC–Universidad de Zaragoza（阿拉贡纳米科学与材料研究所（CSIC-萨拉戈萨大学））；Physikalisches Institut, University of Tübingen（蒂宾根大学物理学院）
We investigate the stability of few-electron quantum phases in vertically coupled quantum dots under a magnetic field of arbitrary strength and direction. The orbital and spin stability diagrams of realistic devices containing up to five electrons, from strong to weak inter-dot coupling, is determined. Correlation effects and realistic sample geometries are fully taken into account within the Full Configuration Interaction method. In general, the magnetic field drives the system into a strongly correlated regime by modulating the single-particle gaps. In coupled quantum dots different componen…
Enhancing the Energy Resolution in Scanning Tunneling Microscopy: from dynamical Coulomb blockade to cavity quantum electrodynamics
Max-Planck-Institut für Festkörperforschung（马克斯·普朗克固体研究所）；Institute for Complex Quantum Systems and IQST, Universität Ulm（乌尔姆大学复杂量子系统与IQST研究所）；Institut de Physique, Ecole Polytechnique Fédérale de Lausanne（洛桑联邦理工学院物理研究所）
We describe a versatile toolbox for the quantum simulation of many-body lattice models, capable of exploring the combined effects of background Abelian and non-Abelian gauge fields, bond and site disorder, and strong on-site interactions. We show how to control the quantum dynamics of particles trapped in lattice potentials by the photon-assisted tunneling induced by periodic drivings. This scheme is general enough to be applied to either bosons or fermions with the additional advantage of being non-perturbative. It finds an ideal application in microfabricated ion trap arrays, where the quant…
The interplay between discrete vibrational and electronic degrees of freedom directly influences the chemical and physical properties of molecular systems. This coupling is typically studied through optical methods such as fluorescence, absorption, and Raman spectroscopy. Molecular electronic devices provide new opportunities for exploring vibration-electronic interactions at the single molecule level. For example, electrons injected from a scanning tunneling microscope tip into a metal can excite vibrational excitations of a molecule in the gap between tip and metal. Here we show how current …
Electrically driven plasmon-polaritonic bistability in Dirac electron tunneling transistors
Columbia University（哥伦比亚大学）；ETH Zürich（苏黎世联邦理工学院）；National Institute for Materials Science（国立材料研究所）；Air Force Research Laboratory（空军研究实验室）；ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology（巴塞罗那光子科学研究所，巴塞罗那科学技术研究院）；ICREA-Institució Catalana de Recerca i Estudis Avançats（加泰罗尼亚高级研究学院）
We report on the study of the electrical current flowing in weakly coupled superlattice (SL) structures under an applied electric field at very low temperature, i.e. in the tunneling regime. This low temperature transport is characterized by an extremely low tunneling probability between adjacent wells. Experimentally, I(V) curves at low temperature display a striking feature, i.e a plateau or null differential conductance. A theoretical model based on the evaluation of scattering rates is developed in order to understand this behaviour, exploring the different scattering mechanisms in AlGaAs …
We consider the phenomenon of quantum charge pumping of electrons across a superconducting double barrier structure in graphene in the adiabatic limit. In this geometry, quantum charge pumping can be achieved by modulating the amplitudes (Delta_1 and Delta_2) of the gaps associated with the two superconducting strips. We show that the superconducting gaps give rise to a transmission resonance in the Delta_1-Delta_2 plane, resulting in a large value of pumped charge, when the pumping contour encloses the resonance. This is in sharp contrast to the case of charge pumping in a normal double barri…
In the Quantum Hall regime, near integer filling factors, electrons should only be transmitted through spatially-separated edge states. However, in mesoscopic systems, electronic transmission turns out to be more complex, giving rise to a large spectrum of magnetoresistance oscillations. To explain these observations, recent models put forward that, as edge states come close to each other, electrons can hop between counterpropagating edge channels, or tunnel through Coulomb islands. Here, we use scanning gate microscopy to demonstrate the presence of quantum Hall Coulomb islands, and reveal th…
The coupling between multiple nanocavities in close vicinity leads to hybridization of their modes. Stacked Metal/Insulator/Metal (MIM) nanocavities constitute a highly versatile and very interesting model system to study and engineer such mode coupling, since they can be realized by lithography-free fabrication methods with fine control on the optical and geometrical parameters. The resonant modes of such MIM cavities are epsilon-near-zero (ENZ) resonances, which are appealing for non-linear photophysics and a variety of applications. Here we study the hybridization of ENZ resonances in MIMIM…
Spin-split superconductivity in spin-orbit coupled hybrid nanowires with ferromagnetic barriers
University of Copenhagen（哥本哈根大学）；Centro de Física de Materiales Centro Mixto CSIC-UPV/EHU（CSIC-UPV/EHU联合材料物理中心）；NNF Quantum Computing Programme, Niels Bohr Institute（尼尔斯·玻尔研究所NNF量子计算项目）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）
Deterministic non-local parity control and supercurrent-based detection in an Andreev molecule
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所凝聚态物理国家实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Hefei National Laboratory（合肥国家实验室）；State Key Laboratory of Semiconductor Physics and Chip Technologies, Institute of Semiconductors, Chinese Academy of Sciences（中国科学院半导体研究所半导体物理与芯片技术国家重点实验室）；State Key Laboratory of Spintronics, Hangzhou International Innovation Institute, Beihang University（北京航空航天大学杭州国际创新研究院自旋电子学国家重点实验室）
Most classical dynamical systems are chaotic. The trajectories of two identical systems prepared in infinitesimally different initial conditions diverge exponentially with time. Quantum systems, instead, exhibit quasi-periodicity due to their discrete spectrum. Nonetheless, the dynamics of quantum systems whose classical counterparts are chaotic are expected to show some features that resemble chaotic motion. Among the many controversial aspects of the quantum-classical boundary, the emergence of chaos remains among the least experimentally verified. Time-resolved observations of quantum chaot…
We established a theoretical framework in terms of the curl flux, population landscape, and coherence for non-equilibrium quantum systems at steady state, through exploring the energy and charge transport in molecular processes. The curl quantum flux plays the key role in determining transport properties and the system reaches equilibrium when flux vanishes. The novel curl quantum flux reflects the degree of non-equilibriumness and the time-irreversibility. We found an analytical expression for the quantum flux and its relationship to the environmental pumping (non-equilibriumness quantified b…
Quadrupolar and dipolar phases of excitons in transition-metal dichalcogenide trilayer heterostructures
The Racah Institute of Physics, The Hebrew University of Jerusalem（拉卡物理研究所，耶路撒冷希伯来大学）；Department of Physics, Technion（理工学院物理系）；The Fritz Haber Research Center for Molecular Dynamics, The Hebrew University of Jerusalem（分子动力学弗里茨·哈伯研究中心，耶路撒冷希伯来大学）
