Visualization of Chiral Electronic Structure and Anomalous Optical Response in a Material with Chiral Charge Density Waves

TL;DR

This paper visualizes the chiral electronic structure and optical responses in a layered material with chiral charge density waves, revealing new insights into its physical properties and potential applications in optics and spintronics.

Contribution

It provides the first spectroscopic visualization of chiral electronic bands and optical responses in a CDW phase of 1T-TaS2, linking chiral symmetry to observable phenomena.

Findings

Chiral electronic band structure with windmill-shaped Fermi surfaces identified.

Chirality-dependent circularly polarized Raman response observed.

Chiral Fermi surfaces and Raman responses coincide with the CDW transition.

Abstract

Chiral materials have attracted significant research interests as they exhibit intriguing physical properties, such as chiral optical response, spin-momentum locking and chiral induced spin selectivity. Recently, layered transition metal dichalcogenide 1T-TaS2 has been found to host a chiral charge density wave (CDW) order. Nevertheless, the physical consequences of the chiral order, for example, in electronic structures and the optical properties, are yet to be explored. Here, we report the spectroscopic visualization of an emergent chiral electronic band structure in the CDW phase, characterized by windmill-shape Fermi surfaces. We uncover a remarkable chirality-dependent circularly polarized Raman response due to the salient chiral symmetry of CDW, although the ordinary circular dichroism vanishes. Chiral Fermi surfaces and anomalous Raman responses coincide with the CDW transition, proving their lattice origin. Our work paves a path to manipulate the chiral electronic and optical properties in two-dimensional materials and explore applications in polarization optics and spintronics.