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Crossover phenomenon for hopping conduction in strong magnetic fields

1992; American Physical Society; Volume: 68; Issue: 20 Linguagem: Inglês

10.1103/physrevlett.68.3076

1092-0145

I. Shlimak, M. Kaveh, M. Yosefin, Michael Lea, P. Fozooni,

Physics of Superconductivity and Magnetism

We find that strong magnetic fields reduce the effectiveness of the Coulomb gap in determining the variable-range-hopping (VRH) resistivity \ensuremath{\rho}. We propose a crossover phenomenon characterized by a temperature ${\mathit{T}}_{\mathit{c}}$ with the Coulomb gap affecting the VRH resistivity only below ${\mathit{T}}_{\mathit{c}}$. The value of ${\mathit{T}}_{\mathit{c}}$ decreases as the magnetic field increases. Our theoretical model explains the observed crossover from a ln\ensuremath{\rho}(H=0)\ensuremath{\propto}${\mathit{T}}^{\mathrm{\ensuremath{-}}1/2}$ law to a ln\ensuremath{\rho}(H)\ensuremath{\propto}[${\mathit{T}}_{0}$(H)/T${]}^{1/3}$ law with ${\mathit{T}}_{0}$\ensuremath{\propto}H.