THE EFFECTS OF MACROSCOPIC DISORDER IN CONDENSED MATTER SYSTEMS

Abstract

The presence of macroscopic disorder in condensed matter systems has been of great experimental and theoretical interest in recent years. In particular, the electrical conductivity and the magnetoconductivity (electrical conductivity in the presence of a magnetic field) are substantially altered due to the presence of macroscopic inhomogeneity. In this work, we investigate the role of disorder in graphene and Dirac semimetals and treat it using an Effective Medium Theory (EMT) formalism. The transverse magnetoresistance (MR) seen in these systems is shown to arise purely as a consequence of the macroscopic inhomogeneities present. Experimental data from graphene and TlBiSSe are used to make both qualitative and quantitative comparisons with the theory presented. We also provide a simple physical intuition that captures the essential physics of disorder induced MR. Lastly, we compare the EMT to an alternative formalism, namely the Random Resistor Network (RRN), and show that the two theoretical models are equivalent.