arXiv subjects

R. Berkovits

Publications and source records attributed to R. Berkovits.

24 records · Page 2Linked to original sources

arXiv1997

Localization in Fock space: A finite size scaling hypothesis for many particle excitation statistics

The concept of localization in Fock space is extended to the study of the many particle excitation statistics of interacting electrons in a two dimensional quantum dot. In addition, a finite size scaling hypothesis for Fock space localization, in which the excitation energy replaces the system size, is developed and tested by analyzing the spectral properties of the quantum dot. This scaling hypothesis, modeled after the usual Anderson transition scaling, fits the numerical data obtained for the interacting states in the dot. It therefore attests to the relevance of the Fock space localization scenario to the description of many particle excitation properties.

cond-mat.mes-hall↗

arXiv1997

The Conductance in the One Dimensional Spin Polarized Gas

We present a theoretical analysis of the recent experimental results of Thomas et al on transport properties of spin polarized quantum wires. We suggest an explanation of the observed deviations of the conductance from the universal value $G=2e^2/h$ per channel in the wire. We argue that the new quasi plateau observed for the conductance at the value $G=1.4e^2/h$ is a result of the proximity between the spin polarized phase and the metallic one. The enhancement of the conductance from the value $G=e^2/h$ to $G=1.4e^2/h$ is due to the hybridization of the electronic state at $K_F^{\downarrow}\approx 0$ with the chiral states at $K_F^{\uparrow}$ and $-K_F^{\uparrow}$.

cond-mat.str-el↗

arXiv1996

Persistent currents in continuous one-dimensional disordered rings within the Hartree--Fock approximation

We present numerical results for the zero temperature persistent currents carried by interacting spinless electrons in disordered one dimensional continuous rings. The disorder potential is described by a collection of delta-functions at random locations and strengths. The calculations are performed by a self-consistent Hartree-Fock (H-F) approximation. Because the H-F approximation retains the concept of single-electron levels, we compare the statistics of energy levels of noninteracting electrons with those of interacting electrons as well as of the level persistent currents. We find that the e-e interactions alters the levels and samples persistent currents and introduces a preffered diamagnetic current direction. In contrast to the analogous calculations that recently appeared in the literature for interacting spinless electrons in the presence of moderate disorder in tight-binding models we find no suppression of the persistent currents due to the e-e interactions.

cond-mat.mes-hall↗

arXiv1996

Compressibility, capacitance and ground state energy fluctuations in a weakly interacting quantum dot

We study the effect of electron-electron (e-e) interactions on compressibility, capacitance and inverse compressibility of electrons in a quantum dot or a small metallic grain. The calculation is performed in the random-phase approximation. As expected, the ensemble-averaged compressibility and capacitance decreases as a function of the interaction strength, while the mean inverse compressibility increases. Fluctuations of the compressibility are found to be strongly suppressed by the e-e interactions. Fluctuations of the capacitance and inverse compressibility also turn out to be much smaller than their averages. The analytical calculations are compared with the results of a numerical calculation for the inverse compressibility of a disordered tight-binding model. Excellent agreement for weak interaction values is found. Implications for the interpretation of current experimental data are discussed.

cond-mat.mes-hall↗

arXiv1996

Even-odd correlations in capacitance fluctuations of quantum dots

We investigate effects of short range interactions on the addition spectra of quantum dots using a disordered Hubbard model. A correlation function \cS(q) is defined on the inverse compressibility versus filling data, and computed numerically for small lattices. Two regimes of interaction strength are identified: the even/odd fluctuations regime typical of Fermi liquid ground states, and a regime of structureless $\cS(q)$ at strong interactions. We propose to understand the latter regime in terms of magnetically correlated localized spins.

cond-mat↗

arXiv1996

Chaotic Signatures in the Spectrum of a Quantum Double Well

The spectrum of a double well constructed of a square barrier embedded in an infinite well is analyzed. Level statistics for levels slightly above the barrier show signs of Wigner statistics usually associated with quantum chaos. The correspondence with Wigner statistics improves when an ensemble of systems with slightly different barrier heights is taken, possibly reflecting an adiabatic time-dependent modulation of the barrier.

cond-mat↗