arXiv subjects

L. I. Glazman

Publications and source records attributed to L. I. Glazman.

122 records · Page 7Linked to original sources

arXiv1996

Re-entrant resonant tunneling

We study the effect of electron-electron interactions on the resonant-tunneling spectroscopy of the localized states in a barrier. Using a simple model of three localized states, we show that, due to the Coulomb interactions, a single state can give rise to two resonant peaks in the conductance as a function of gate voltage, G(Vg). We also demonstrate that an additional higher-order resonance with Vg-position in between these two peaks becomes possibile when interactions are taken into account. The corresponding resonant-tunneling process involves two-electron transitions. We have observed both these effects in GaAs transistor microstructures by studying the time evolution of three adjacent G(Vg) peaks caused by fluctuating occupation of an isolated impurity (modulator). The heights of the two stronger peaks exibit in-phase fluctuations. The phase of fluctuations of the smaller middle peak is opposite. The two stronger peaks have their origin in the same localized state, and the third one corresponds to a co-tunneling process.

cond-mat↗

arXiv1996

Theory of Andreev reflection in a junction with a strongly disordered semiconductor

We study the conduction of a {\sl N~-~Sm~-~S} junction, where {\sl Sm} is a strongly disordered semiconductor. The differential conductance $dI/dV$ of this {\sl N~-~Sm~-~S} structure is predicted to have a sharp peak at $V=0$. Unlike the case of a weakly disordered system, this feature persists even in the absence of an additional (Schottky) barrier on the boundary. The zero-bias conductance of such a junction $G_{NS}$ is smaller only by a numerical factor than the conductance in the normal state $G_N$. Implications for experiments on gated heterostructures with superconducting leads are discussed.

cond-mat↗

arXiv1995

Two-electron state in a disordered 2D island: pairing caused by the Coulomb repulsion

We show the existence of bound two-electron states in an almost depleted two-dimensional island. These two-electron states are carried by special compact configurations of four single-electron levels. The existence of these states does not require phonon mediation, and is facilitated by the disorder-induced potential relief and by the electron-electron repulsion only. The density of two-electron states is estimated and their evolution with the magnetic field is discussed.

cond-mat↗

arXiv1995

Coulomb Blockade of Tunneling Through a Double Quantum Dot

We study the Coulomb blockade of tunneling through a double quantum dot. The temperature dependence of the linear conductance is strongly affected by the inter-dot tunneling. As the tunneling grows, a crossover from temperature-independent peak conductance to a power-law suppression of conductance at low temperatures is predicted. This suppression is a manifestation of the Anderson orthogonality catastrophe associated with the charge re-distribution between the dots, which accompanies the tunneling of an electron into a dot. We find analytically the shapes of the Coulomb blockade peaks in conductance as a function of gate voltage.

cond-mat↗

arXiv1995

Zero-bias Anomaly of Tunneling into the Edge of a 2D Electron System

We investigate the electron tunneling into the edge of a clean weakly interacting two-dimensional electron gas. It is shown that the corresponding differential conductance $G(V)$ has a cusp at zero bias, and is characterized by a universal slope $|dG/dV|$ at $V=0$. This singularity originates from the electron scattering on the Friedel oscillation caused by the boundary of the system.

cond-mat↗

arXiv1995

Two - Dimensional Electron Liquid in a Weak Magnetic Field

We present an effective theory describing the low-energy properties of an interacting 2D electron gas at large non-integer filling factors $ν\gg 1$. Assuming that the interaction is sufficiently weak, $r_s < 1$, we integrate out all the fast degrees of freedom, and derive the effective Hamiltonian acting in the Fock space of the partially filled Landau level only. This theory enables us to find two energy scales controlling the electron dynamics at energies less than $\hbarω_c$. The first energy scale, $(\hbarω_c/ν)\ln\left(νr_s\right)$, appears in the one electron spectral density as the width of a pseudogap. The second scale, $r_s\hbarω_c$, is parametrically larger; it characterizes the exchange-enhanced spin splitting and the thermodynamic density of states.

cond-mat↗

arXiv1995

Negative hopping magnetoresistance of two-dimensional electron gas in a smooth random potential

We show that the tunnel coupling between semiclassical states localized in different minima of a smooth random potential increases when magnetic field is applied. This increase originates from the difference in gauge factors which electron wave functions belonging to different electron ``lakes'' acquire in the presence of the field. We illustrate the increase of coupling by a model calculation of tunneling through a saddle point separating two adjacent lakes. In the common case, when the barrier between two lakes is much narrower than their size, the characteristic magnetic field is determined by the area of the lakes, and thus may be quite small. The effect of the field on coupling constants leads to a negative magnetoresistance in low-temperature conduction.

cond-mat↗

arXiv1995

TUNNELING SPECTROSCOPY OF QUANTUM CHARGE FLUCTUATIONS IN THE COULOMB BLOCKADE

We present a theory of Coulomb blockade oscillations in tunneling through a pair of quantum dots connected by a tunable tunneling junction. The positions and amplitudes of peaks in the linear conductance are directly related, respectively, to the ground state energy and to the dynamics of charge fluctuations. We study analytically both strong and weak interdot tunneling. As the tunneling decreases, the period of the peaks doubles, as observed experimentally. In the strong tunneling limit, we predict a striking power law temperature dependence of the peak amplitudes.

cond-mat↗

arXiv1995

Theory of hopping magnetoresistance induced by Zeeman splitting

We present a study of hopping conductivity for a system of sites which can be occupied by more than one electron. At a moderate on-site Coulomb repulsion, the coexistence of sites with occupation numbers 0, 1, and 2 results in an exponential dependence of the Mott conductivity upon Zeeman splitting $μ_BH$. We show that the conductivity behaves as $\lnσ= (T/T_0)^{1/4}F(x)$, where $F$ is a universal scaling function of $x=μ_BH/T(T_0/T)^{1/4}$. We find $F(x)$ analytically at weak fields, $x \ll 1$, using a perturbative approach. Above some threshold $x_{\rm th}$, the function $F(x)$ attains a constant value, which is also found analytically. The full shape of the scaling function is determined numerically, from a simulation of the corresponding ``two color'' dimensionless percolation problem. In addition, we develop an approximate method which enables us to solve this percolation problem analytically at any magnetic field. This method gives a satisfactory extrapolation of the function $F(x)$ between its two limiting forms.

cond-mat↗

arXiv1994

Andreev Spectroscopy of Josephson Coupling

It is shown that the low energy spectrum of mesoscopic superconductors coupled by Josephson interaction can be probed by two-electron tunneling from a normal electrode. The Andreev reflection in the NS junction of a normal-superconductor-superconductor double junction (NSS transistor) provides a unique spectroscopic tool to probe the coherent Cooper pair tunneling and the energy spectrum of the Josephson (SS) junction. The ground state properties are reflected in a resonant structure of the linear conductance; excited states with an energy as low as the Josephson coupling energy lead to a threshold in the nonlinear $I$-$V$ characteristic.

cond-mat↗

arXiv1994

Tunneling into a Two-Dimensional Electron Liquid in a Weak Magnetic Field

We study the spectral density function of a two-dimensional electron liquid in a weak magnetic field, the filling factor $ν\gg 1$. A hydrodynamic model for low-energy excitations of the liquid is developed. It is found that even at $ν\gg 1$ the density of states exhibits a gap at low energies. Its width $2E_0$ depends on the strength of interaction only logarithmically, $2E_0=(\hbarω_c/ν)\ln (νe^2/\varepsilon\hbar v_F)$. The effects of temperature and disorder on the density of states are discussed.

cond-mat↗

arXiv1993

Novel Edge Excitations of Two-dimensional Electron Liquid in a Magnetic Field

We investigate the low-energy spectrum of excitations of a compressible electron liquid in a strong magnetic field. These excitations are localized at the periphery of the system. The analysis of a realistic model of a smooth edge yields new branches of acoustic excitation spectrum in addition to the well known edge magnetoplasmon mode. The velocities are found and the observability conditions are established for the new modes.

cond-mat↗

arXiv1993

Fermi Edge Singularities and Backscattering in a Weakly Interacting 1D Electron Gas

The photon-absorption edge in a weakly interacting one-dimensional electron gas is studied, treating backscattering of conduction electrons from the core hole exactly. Close to threshold, there is a power-law singularity in the absorption, $I(ε) \propto ε^{-α}$, with $α= 3/8 + δ_+/π- δ_+^2/2π^2$ where $δ_+$ is the forward scattering phase shift of the core hole. In contrast to previous theories, $α$ is finite (and universal) in the limit of weak core hole potential. In the case of weak backscattering $U(2k_F)$, the exponent in the power-law dependence of absorption on energy crosses over to a value $α= δ_+/π- δ_+^2/2π^2$ above an energy scale $ε^* \sim [U(2k_F)]^{1/γ}$, where $γ$ is a dimensionless measure of the electron-electron interactions.

cond-mat↗

arXiv1993

Tunneling in One-Dimensional non-Luttinger Electron Liquid

The conductance of a weakly interacting electron gas in the presense of a single scatterer is found at arbitrary strength of the scattering potential. At weak interaction, a simple renormalization group approach can be used instead of the standard bosonization procedure. Our technique allows to take into account the {\em backscattering\/} of electrons that leads to a non-Luttinger-liquid behavior of the low-temperature conductance. In the presence of magnetic field, the backscattering may give rise to a peak in differential conductance at bias equal to the Zeeman energy.

cond-mat↗