Conductivity and Resistivity of Dirac Electrons in Single-Component Molecular Conductor [Pd(dddt)_2]

TL;DR

This study investigates the electrical properties of Dirac electrons in the molecular conductor [Pd(dddt)_2], revealing how pressure influences conductivity and resistivity, with findings explaining experimental observations of pseudogap behavior.

Contribution

It provides a theoretical analysis of Dirac electron transport in [Pd(dddt)_2], highlighting pressure-dependent conductivity and pseudogap phenomena using a tight-binding model.

Findings

Conductivity increases linearly at low T under pressure due to Dirac cones.

Resistivity shows pseudogap-like behavior even with Dirac electrons.

Pressure influences the transition between semimetal and insulator states.

Abstract

Dirac electrons, which have been found in the single-component molecular conductor [Pd(dddt)_2] under pressure, are examined by calculating the conductivity and resistivity in terms of a tight-binding model for several pressures of P GPa, which give a nodal line semimetal or insulator. The temperature (T) dependence of the conductivity shows that the conductivity increases linearly under pressure at low T due to the Dirac cone but stays almost constant at high T. Further, at lower pressures, the conductivity is suppressed due to an unconventional gap, which is examined by calculating the resistivity. The resistivity exhibits a pseudogap-like behavior even in the case described by the Dirac cone. Such behavior originates from a novel role of the nodal line semimetal followed by a pseudogap that is different from a band gap. The present result reasonably explains the resistivity observed in the experiment.