Electrodynamics of tilted Dirac/Weyl materials: A unique platform for unusual surface plasmon polaritons

TL;DR

This paper explores how tilted Dirac and Weyl materials exhibit unique surface plasmon polaritons due to their modified electrodynamics, enabling potential mapping of tilt and Fermi arc features via SPP measurements.

Contribution

It introduces an extended electrodynamics framework for tilted Dirac/Weyl materials and analyzes the resulting unusual surface plasmon polariton spectra.

Findings

SPP spectrum depends on tilt parameter $oldsymbol{}$ in tilted Dirac materials.

Unusual spectral features of SPP modes in tilted Weyl semimetals.

SPP spectra can be used to map tilt and Fermi arc characteristics.

Abstract

The electrodynamics of Weyl semimetals (WSMs) is an extension of Maxwell's theory where in addition to field strength tensor $F_{\mu\nu}$, an axion field enters the theory which is parameterized by a four-vector $b^\mu=(b_0,\bf b)$. In the tilted Weyl matter (TWM) an additional set of parameters ${\bf\zeta}=(\zeta_x,\zeta_y,\zeta_z)$ enter the theory that can be encoded into the metric of the spacetime felt by electrons in TWM. This allows an extension of Maxwell's electrodynamics that describes electric and magnetic fields in TWMs and tilted Dirac material (TDM) when $b^\mu=0$. The tilt parameter $\bf\zeta$ appearing as off-diagonal metric entries mixing time and space components mingles $\bf E$ and $\bf B$ fields whereby modifies the inhomogeneous Maxwell's equations. Surface plasmon polariton (SPP) in these systems describes the propagation of electromagnetic waves at the {\it interface of two different spacetime geometries}. In the case of TDM, we find a characteristic dependence of SPP spectrum on the tilt parameter $\zeta$ which can be used map $\zeta$ from SPP measurements. In the case of TWM, depending on whether the interface with vacuum supports a Fermi arc or not, and whether the propagation direction is along the Fermi arc or transverse to it, we find many unusual spectral features for SPP modes. Our detailed study of the dependence of SPP spectra on the arrangements of three vectors $(\bf b, q,\zeta)$, the first two of which are at our control, can be utilized to map the tilt characteristics and Fermi arc characteristics from SPP measurements.