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A L Efros

Publications and source records attributed to A L Efros.

7 recordsLinked to original sources
PubMed2004

Comment II on "Resonant and antiresonant frequency dependence of the effective parameters of metamaterials".

In a recent paper, Koshny, Markos, Smith, and Soukoulis [Phys. Rev E 68, 065602 (2003)] report that their computations show that the product of imaginary parts of electric permittivity and magnetic permeability in a passive media is negative. They also criticize a well-known theorem that both imaginary parts are positive as a result of the second law of thermodynamics. I argue that this criticism has no ground and that computational evidence may result from inadequate introduction of the very concept of epsilon (omega) and mu (omega) in a photonic crystal.

Comment↗
PubMed2002

Electrodynamics of metallic photonic crystals and the problem of left-handed materials.

An analytical theory of low frequency electromagnetic waves in metallic photonic crystals with a small volume fraction of a metal is presented. The evidence for such waves has been obtained recently by experiments and computations. The cutoff frequency of these waves, omega(0), is studied. An analytical expression for the permittivity epsilon is obtained and shown to be negative below omega(0). If the crystal is embedded into a medium with a negative mu, there are no propagating modes at any frequency. Thus, such a compound system is not a left-handed material (LHM). The recent experimental results on the LHM are discussed.

Journal Article↗
PubMed2002

Variable range hopping in two-dimensional systems of interacting electrons.

Computer modeling of the variable-range-hopping (VRH) conductivity in two-dimensional systems has been done by a kinetic Monte Carlo method, which includes some new elements. Study of the temperature dependence of the conductivity, testing of the different scaling relations, and study of the size effect show the detailed validity of the Efros-Shklovskii theory of the VRH in the system of interacting electrons. It has also been shown that simultaneous transitions of many electrons are not important. The reasons for disagreement with previous computational works are thoroughly analyzed.

Journal Article↗
PubMed2001

Paramagnetic ion-doped nanocrystal as a voltage-controlled spin filter.

A theory of spin injection from a ferromagnetic source into a semiconductor through a paramagnetic ion-doped nanocrystal is developed. Spin-polarized current from the source polarizes the ion; the polarized ion, in turn, controls the spin polarization of the current flowing through the nanocrystal. Depending on voltage, the ion can either enhance the injection coefficient by several times or suppress it. Large ion spins produce stronger enhancement of spin injection.

Journal Article↗
PubMed2001

Electron and nuclear spin interactions in the optical spectra of single GaAs quantum dots.

Fine and hyperfine splittings arising from electron, hole, and nuclear spin interactions in the magneto-optical spectra of individual localized excitons are studied. We explain the magnetic field dependence of the energy splitting through competition between Zeeman, exchange, and hyperfine interactions. An unexpectedly small hyperfine contribution to the splitting close to zero applied field is described well by the interplay between fluctuations of the hyperfine field experienced by the nuclear spin and nuclear dipole/dipole interactions.

Journal Article↗
PubMed2001

New class of magnetoresistance oscillations: interaction of a two-dimensional electron gas with leaky interface phonons.

We report on a new class of magnetoresistance oscillations observed in a high-mobility two-dimensional electron gas (2DEG) in GaAs-Al(x)Ga(1--x)As heterostructures. Appearing in a weak magnetic field ( B < 0.3 T) and only in a narrow temperature range ( 2 K < T < 9 K), these oscillations are periodic in 1/B with a frequency proportional to the electron Fermi wave vector, k(F). We interpret the effect as a magnetophonon resonance of the 2DEG with leaky interface-acoustic phonon modes carrying a wave vector q = 2k(F). Calculations show a few branches of such modes existing on the GaAs-Al(x)Ga(1--)xAs interface, and their velocities are in quantitative agreement with the observation.

Journal Article↗