Magnetic field induced coherence-incoherence crossover in the interlayer conductivity of a layered organic metal

Abstract

The angle-dependent interlayer magnetoresistance of the pressurized (to the normal metallic state) layered organic metal $\ensuremath{\alpha}\text{\ensuremath{-}}{(\text{BEDT-TTF})}_{2}\text{KHg}{(\text{SCN})}_{4}$ is found to change from the conventional behavior at low magnetic fields to an anomalous one at high fields. The dependence of this field-induced crossover on the sample purity and temperature reveals parallel contribution of the classical Boltzmann and incoherent channels in the interlayer conductivity. The latter channel, having a metallic temperature dependence but being insensitive to an in-plane magnetic field, may be responsible for magnetoresistance anomalies observed in a number of layered metals. We propose a possible mechanism for the incoherent channel combining interlayer tunneling via local hopping centers and intralayer diffusion.