Waveguide modes in Weyl semimetals with tilted Dirac cones
Klaus Halterman and Mohammad Alidoust
Opt. Express 27, 36164 (2019). [PDF]Wetheoreticallystudyunattenuatedelectromagneticguidedwavemodesincentrosym- metric Weyl semimetal layered systems. By solving Maxwell’s equations for the electromagnetic fields and using the appropriate boundary conditions, we derive dispersion relations for propagat- ing modes in a finite-sized Weyl semimetal. Our findings reveal that for ultrathin structures and proper Weyl cones tilts, extremely localized guided waves can propagate along the semimetal interface over a certain range of frequencies. This follows from the anisotropic nature of the semimetal where the diagonal components of the permittivity can exhibit a tunable epsilon-near- zero response. From the dispersion diagrams, we determine experimentally accessible regimes that lead to high energy-density confinement in the Weyl semimetal layer. Furthermore, we show that the net system power can vanish all together, depending on the Weyl cone tilt and frequency of the electromagnetic wave. These effects are seen in the energy transport velocity, which demonstrates a substantial slowdown in the propagation of electromagnetic energy near critical points of the dispersion diagrams. Our results can provide guidelines in designing Weyl semimetal waveguides that can offer efficient control in the velocity and direction of energy flow.
