Realizing Giant Magneto-Optical Effects in 3D Topological Insulators Without Magnetic Fields

TL;DR

This paper demonstrates large magneto-optical effects in 3D topological insulators without magnetic fields by exploiting surface state interactions and symmetry breaking, revealing potential for novel optical devices.

Contribution

It introduces a new approach to achieve giant magneto-optical effects in topological insulators through surface state interactions without magnetic fields.

Findings

Observed large Faraday rotation in Sb2Te3 crystals.

Attributed polarization rotation to Kerr effect at TI-fiber interface.

Showed effects arise from symmetry breaking and surface electron interactions.

Abstract

Topological insulators display unusual light-matter interactions due to the helical nature of surface electronic states. We study the near-field interaction of light propagating in an optical fiber with crystals of Sb2Te3, a 3D topological insulator (TI), and observe a large apparent Faraday rotation. The origin of this unexpected polarization rotation in the optical fiber is attributed to a magneto-optical Kerr effect at the TI-fiber interface. We show that the combined effects of time-reversal symmetry breaking, which arises from Zeeman coupling of the electromagnetic field with the surface electrons of the TI, and inversion symmetry breaking of optical excitations, which arises from the exponential decay of the evanescent light across the TI crystal, are central to realizing this giant polarization rotation. Our work demonstrates a facile approach for realizing large magneto-optical effects without any magnetic fields by exploiting the unique physics of light-matter interactions at TI surfaces.