Chiralometer: Direct Torque Detection of Crystal Chirality

TL;DR

The paper introduces the Chiralometer, a novel mechanical method to directly detect crystal chirality by measuring torque induced by angular momentum imbalance, applicable to various chiral materials.

Contribution

It proposes a new mechanical detection technique for crystal chirality using torque measurements driven by temperature gradients or electric fields.

Findings

Mechanical torque detectable with modern sensors in chiral crystals.

Temperature gradients and electric fields induce measurable angular momentum imbalance.

Signatures identified in materials like Te, SiO2, and CoSi.

Abstract

Chirality governs phenomena ranging from chemical reactions to the topology of quasiparticle charge carriers. However, a direct macroscopic probe for crystal chirality remains a significant challenge, especially in time reversal symmetric systems with weak circular dichroism signal. Here, we propose the ``Chiralometer'', a mechanical detection method that probes chirality by driving angular momentum carriers out of equilibrium. Using first-principles calculations and semiclassical transport theory, we demonstrate that a temperature gradient in insulators or an electric field in metals induces uncompensated angular momentum in phonons and electrons, respectively. This imbalance generates a macroscopic mechanical torque ($\tau \sim 10^{-11} N \cdot m$) well within the sensitivity of modern torque magnetometry and cantilever-based sensors. We identify robust signatures in chiral crystals such as Te, SiO$_2$, and the topological semimetal CoSi. Our work establishes mechanical torque as a fundamental order parameter for chirality, offering a transformative tool for orbitronics and chiral quantum materials.