Shubnikov-de Haas oscillations, peaks and different temperature regimes of the diagonal conductivity in the integer quantum Hall conductor

Анотація

A theory for the Shubnikov—de Haas oscillations in the diagonal conductivity s_xx of a 2D conductor is developed for the case when electron states within the broaden Landau levels are localized except the narrow stripe in the center. The standard Shubnikov—de Haas oscillations take place only in the low-field region which at higher magnetic fields crosses over into peaks. In the limit Wt >> 1 peaks in the s_xx became sharp and between them s_xx → 0 (W is the cyclotron frequency, t is the electron scattering time). The conductivity peaks display different temperature behavior with the decrease of temperature, T: a thermal activation regime, s_xx µexp(-D/T), which holds at higher temperatures, crosses over into the variable-range-hopping regime at lower temperatures with s_xxµ1/Texp(-√ T₀/T)(the prefactor 1/T is absent in the conductance).