Tilting flat bands in an empty microcavity

TL;DR

This paper demonstrates that flat bands and spin-dependent tilting can be achieved in an empty microcavity through mode interactions and refractive index distribution, without the need for birefringent materials.

Contribution

It reveals that mode anticrossing and specific refractive index profiles can produce flat bands and spin-dependent effects in simple microcavities without anisotropic layers.

Findings

Flat bands are observed within the energy gap.

Mode squeezing due to TE-TM and XY splitting causes spin-dependent tilting.

Mode interactions can induce flat bands without birefringent materials.

Abstract

Recently microcavities with anisotropic materials are shown to be able to create novel bands with non-zero local Berry curvature. The anisotropic refractive index of the cavity layer is believed to be critical in opening an energy gap at the tilted Dirac points. In this work, we show that an anticrossing between a cavity mode and a Bragg mode can also form within an empty microcavity without any birefringent materials. Flat bands are observed within the energy gap due to the particular refractive index distribution of the sample. The intrinsic TE-TM splitting and XY splitting induce the squeezing of the cavity modes in momentum space, so that the flat bands are spin-dependently tilted. Our results pave the way to investigate the spin orbit coupling of photons in a simple microcavity without anisotropic cavity layers.