Purely Electronic Chirality without Structural Chirality

TL;DR

This paper introduces the concept of purely electronic chirality (PEC), demonstrating its existence in electronic orders without structural asymmetry, and explores its implications and observable effects in condensed matter systems.

Contribution

It presents the theoretical concept of PEC, analyzes a model with quadrupole orders on a kagomé lattice, and predicts chirality-related responses and phonon phenomena arising from PEC.

Findings

Chirality can originate purely from electronic order without structural asymmetry.

Predicted chirality-related responses in URhSn due to quadrupole order.

Chiral phonons can emerge via coupling with PEC in achiral crystals.

Abstract

We introduce the concept of purely electronic chirality (PEC), which arises in the absence of structural chirality. In condensed matter physics and chemistry, chirality has conventionally been understood as a mirror-image asymmetry in crystal or molecular structures. We demonstrate that certain electronic orders exhibit chirality-related properties without atomic displacement. Specifically, we investigate quadrupole orders to realize such purely electronic chirality with handedness that can be tuned by magnetic fields. As a representative example, we analyze a model featuring $120^circ$ antiferro quadrupole orders on a distorted kagom\'e lattice, predicting various chirality-related responses in the nonmagnetic ordered phase of URhSn. Furthermore, as a phonon analog, chiral phonons can emerge in achiral crystals through coupling with the PEC order. Our results provide a distinct origin of chirality and a fundamental basis for exploring the interplay between electronic and structural chirality.