THEORY OF HOPPING MAGNETORESISTANCE INDUCED BY ZEEMAN SPLITTING

Citation
Ka. Matveev et al., THEORY OF HOPPING MAGNETORESISTANCE INDUCED BY ZEEMAN SPLITTING, Physical review. B, Condensed matter, 52(7), 1995, pp. 5289-5297
Citations number
10
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
01631829
Volume
52
Issue
7
Year of publication
1995
Pages
5289 - 5297
Database
ISI
SICI code
0163-1829(1995)52:7<5289:TOHMIB>2.0.ZU;2-X
Abstract
We present a study of hopping conductivity for a system of sites that can be occupied by more than one electron. At a moderate on-site Coulo mb repulsion, the coexistence of sites with occupation numbers 0, 1, a nd 2 results in an exponential dependence of the Mott conductivity upo n Zeeman splitting H-mu B. We show that the conductivity behaves as 1n sigma = (T/T-0)F-1/4(x), where F is a universal scaling function of x = H-mu B/T(T-0/T)(1/4). We find F(x) analytically at weak fields, x m uch less than 1, using a perturbative approach. Above some threshold x (th), the function F(x) attains a constant value, which is also found analytically The full shape of the scaling function is determined nume rically, from a simulation of the corresponding ''two-color'' dimensio nless percolation problem. In addition, we develop an approximate meth od 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.