Fermi-Arc-Induced Vortex Structure in Weyl Beam Shifts

Abstract

In periodic media, despite the close relationship between geometrical effects in the bulk and topological surface states, the two are typically probed separately. We show that when beams in a Weyl medium reflect off an interface with a gapped medium, the trajectory is influenced by both bulk geometrical effects and the Fermi arc surface states. The reflected beam experiences a displacement, analogous to the Goos-Hänchen or Imbert-Fedorov shifts, that forms a half-vortex in the two-dimensional surface momentum space. The half-vortex is centered where the Fermi arc of the reflecting surface touches the Weyl cone, with the magnitude of the shift scaling as an inverse square root away from the touching-point, and diverging at the touching-point. This striking feature provides a way to use bulk transport to probe the topological characteristics of a Weyl medium.

Recent advances in 2D, 3D and higher-order topological photonics

“…Similarly, the interaction between electromagnetic waves and Weyl media has been studied. At the interface of a Weyl medium and an insulator, a reflected beam undergoes an anomalous shift that maps a half-vortex in momentum space influenced by the topological surface states 215 . The phase vortex of the reflected beam was experimentally verified by using a photonic crystal possessing synthetic Weyl points and a Fabry-Perot interference setup (Fig.…”

Electronic non-coplanar refraction and deflected diffraction of Weyl-node-mismatch junctions

“…Since the Weyl semimetal is the 3D counterpart of graphene, the fantasy electron optical effects found in graphene are also expected in Weyl semimetals. The 3D version of Klein tunneling in Weyl materials was studied [19], the negative refraction and the Veselago focusing in Weyl semimetals were discussed [19][20][21][22], and the Imbert-Fedorov shift and Goos-Hänchen shift, for the reflection as well as the transmission in Weyl materials, were reported [23][24][25][26].…”

Vortex of beam shift induced by mono-chiral interface states

“…The electron beam shift on p-n junction interfaces has not only longitudinal but also transverse components, respectively called Goos-Hänchen (GH) and Imbert-Fedorov (IF) shifts, the latter of which does not exist in graphene [30][31][32], and the beam shift for transmission that was not noticed in solid media previously, was pointed out recently [30]. When an electron beam is injected from a Weyl semimetal to an insulator and reflected, the shift is extremely sensitive to the existence of surface bands, and a semi-vortex structure in the in-plane k-space was found locating where the surface band touches and bulk band [33].…”

“…The vortex structure of reflection shift, whose center lies on the edge of the incident circle, is the signal of surface band existence [33]. Since the surface bands of the lower and upper materials meet at the interface, they will merge and reconstruct new interface bands.…”