Magnetoplasmons of the tilted-anisotropic Dirac cone material $\alpha -$(BEDT-TTF)${}_2$I${}_3$

Abstract

We study the collective modes of a low-energy continuum model of the quasi-two-dimensional electron liquid in a layer of the organic compound $\alpha -$(BEDT-TTF)${}_2$I${}_3$ in a perpendicular magnetic field. As testified by zero magnetic field transport experiments and \textit{ab initio} theory, this material hosts both massless and massive low-energy carriers, the former being described by tilted and anisotropic Dirac cones. The polarizability of these cones is anisotropic, and two sets of magnetoplasmon modes occur between any two cyclotron resonances. We show that the tilt of the cones causes a unique intervalley damping effect: the upper hybrid mode of one cone is damped by the particle-hole continuum of the other cone in generic directions. We analyse how the presence of massive carriers affects the response of the system, and demonstrate how doping can tune $\alpha -$(BEDT-TTF)${}_2$I${}_3$ between regimes of isotropic and anisotropic screening.

14 pages, 9 figures

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• Hyperbolic plasmons in massive tilted 2D Dirac materials
• Synthetic non-Abelian gauge fields and gravitomagnetic effects in tilted Dirac cone systems
• Coherent states for graphene under the interaction of crossed electric and magnetic fields
• Dynamical gap generation in 2D Dirac semimetal with deformed Dirac cone
• Surface plasmonics of Weyl semimetals
• Polarizability, plasmons, and screening in 1T${}^{\prime }$-MoS${}_2$ with tilted Dirac bands