Leading role of Dirac cones in transport properties of LaFeAsO

Abstract

Revealing the electronic and magnetic properties of the parent compounds of high-𝑇𝑐 superconductors is a crucial step in understanding unconventional superconductivity. Transport property measurements provide a widely accessible approach to this goal. However, gaining detailed quantitative information from transport experiments often requires a combination of different electric and thermoelectric characterizations as a function of several tuning parameters including magnetic field, temperature, and level of disorder. This is the case of the parent compounds of iron-based superconductors, whose electronic structure is characterized by multiple bands contributing to transport. In this study, we develop an analytical framework for the electric and thermoelectric properties of LaFeAsO by modulating its disorder through neutron irradiation. We demonstrate that, in the low-temperature phase, transport is governed by an 𝑛-type band with Dirac dispersion. These Dirac states could bear relevant information about the roles of antiferromagnetic and nematic fluctuations in the superconducting pairing mechanism. Additionally, we establish a protocol for identifying Dirac cones in the transport properties, which can be applied to the investigation of other fascinating systems, such as Dirac and Weyl semimetals.