Magneto-optics of quasi-relativistic electrons in tilted Dirac cones in graphene and $\alpha$-(BEDT-TTF)$_2$I$_3$

TL;DR

This paper investigates how tilt in Dirac cones affects magneto-optical properties in materials like graphene and organic compounds, revealing that infrared spectra can provide detailed information on the cone structure.

Contribution

It introduces a Lorentz covariant framework to analyze the magneto-optical effects of tilted Dirac cones in various materials, connecting optical spectra to cone tilt characteristics.

Findings

Infrared absorption spectra can quantify Dirac cone tilt.

Tilt modifies the interband transition spectrum from discrete to broad.

Lorentz covariance simplifies the analysis of magneto-optical responses.

Abstract

Massless Dirac fermions occur as low-energy modes in several quasi-two-dimensional condensed matter systems such as graphene, the surface of bulk topological insulators, and in layered organic semiconductors. When the rotational symmetry in such systems is reduced either by an in-plane electric field or an intrinsic tilt of the Dirac cones, the allowed dipolar optical transitions evolve from a few selected transitions into a wide fan of interband transitions. We show that the Lorentz covariance of the low-energy carriers allows for a concise analysis of the emerging magneto-optical properties. We predict that infrared absorption spectra yield quantitative information on the tilted Dirac cone structure in organic compounds such as $\alpha$-(BEDT-TTF)$_2$I$_3$.