arXiv subjects

E. Kogan

Publications and source records attributed to E. Kogan.

44 records · Page 3Linked to original sources

arXiv2007

Effect of motion of the scatterers on localization: quasi localization and quasi mobility edge

We study kinetics of electrons, scattered by heavy particles undergoing slow diffusive motion. In a three-dimensional space we claim the existence of the crossover region (on the energy axis), which separates the states with fast diffusion and the states with slow diffusion; the latter is determined by the dephasing time. In a two-dimensional space the diffusion coefficient for any value of energy is determined by the dephasing time.

cond-mat.dis-nn↗

arXiv2006

Comment on "Spin-Glass Solution of the Double-Exchange Model in Infinite Dimensions"

In a paper submitted to the Arxive some time ago (cond-mat/0509270), R. S. Fishman et al. considered double-exchange model on a Bethe lattice in infinite dimensions using dynamical mean-field theory. We present a somewhat different derivation of their general formula for the magnetic disorder - order transition temperature and comment on the interpretation of the intermediate (between ferromagnetism and antiferromagnetism) phase obtained by the authors.

cond-mat.str-el↗

arXiv2005

Density of states of the interacting two-dimensional electron gas

We study the influence of electron-electron interactions on the density of states (DOS) of clean 2D electron gas. We confirm the linear cusp in the DOS around the Fermi level, which was obtained previously. The cusp crosses over to a pure logarithmic dependence further away from the Fermi surface.

cond-mat.str-el↗

arXiv2005

Probing of the Kondo peak by the impurity charge measurement

We consider the real-time dynamics of the Kondo system after the local probe of the charge state of the magnetic impurity. Using the exactly solvable infinite-degeneracy Anderson model we find explicitly the evolution of the impurity charge after the measurement.

cond-mat.str-el↗

arXiv2005

PM-FM transition in a DE model

We study paramagnetic - ferromagnetic transition due to exchange interaction between classical localized magnetic moments and conduction electrons. By solving the Dynamical Mean Field Approximation equations we find explicit formula for the transition temperature $T_c$ for arbitrary electron dispersion law, concentration and re lation between exchange coupling and the electron band width. We present the results of calculations of the $T_c$ for the semi-circular electron density of states.

cond-mat.str-el↗

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

Measurement of the conductance distribution function at a quantum Hall transition

We study experimentally the reproducible conductance fluctuations between the quantum Hall plateaus in the conductance of two-terminal submicron silicon MOSFETs. For the dramatic fluctuations at the insulator-to-first-plateau transition we find a conductance distribution that is approximately uniform between zero and $e^2/h$. We point out that this is consistent with the prediction of random $S$-matrix theory for a conductor with single-channel leads in a magnetic field.

cond-mat.mes-hall↗

arXiv1996

Distribution Function Analysis of Mesoscopic Hopping Conductance Fluctuations

Variable-range hopping (VRH) conductance fluctuations in the gate-voltage characteristics of mesoscopic GaAs and Si transistors are analyzed by means of their full distribution functions (DFs). The forms of the DF predicted by the theory of Raikh and Ruzin have been verified under controlled conditions for both the long, narrow wire and the short, wide channel geometries. The variation of the mean square fluctuation size with temperature in wires fabricated from both materials is found to be described quantitatively by Lee's model of VRH along a 1D chain. Armed with this quantitative validation of the VRH model, the DF method is applied to the problem of magnetoconductance in the insulating regime. Here a non-monotonic variation of the magnetoconductance is observed in Si MOSFETS whose sign at low magnetic fields is dependent on the channel geometry. The origin of this defect is discussed within the framework of the interference model of VRH magnetoconductance in terms of narrowing of the DF in a magnetic field.

cond-mat↗