Chiral kinematic theory and converse vortical effects

TL;DR

This paper develops a chiral kinematic theory to predict a converse vortical effect, where orbital magnetization is driven by velocity fields, revealing contributions from Berry curvature and Fermi surface magnetic moments, with experimental proposals.

Contribution

It introduces a novel semiclassical and quantum response framework for neutral fermions to a velocity field, predicting the converse vortical effect and identifying its microscopic origins.

Findings

Predicts a converse vortical effect driven by velocity fields.

Identifies Berry curvature and Fermi surface magnetic moments as key contributions.

Proposes CoSi as a candidate material for experimental detection.

Abstract

Response theories in condensed matter typically describe the response of an electron fluid to external electromagnetic fields, while perturbations on neutral particles are often designed to mimic such fields. Here, we study the response of fermions to a space-time-dependent velocity field, thereby sidestepping the issue of gauge charge. First, we use a semiclassical chiral kinematic theory to obtain the local density of current and extract the orbital magnetization. The theory immediately predicts a "converse vortical effect," defined as an orbital magnetization driven by linear velocity. It receives contributions from magnetic moments on the Fermi surface and the Berry curvature of the occupied bands. Then, transcending semiclassics via a complementary Kubo formalism reveals that the uniform limit of a clean system receives only the Berry curvature contribution while other limits sense the Fermi surface magnetic moments too. We propose CoSi as a candidate material and suggest magnetometry of a sample under a thermal gradient to detect the effect. Overall, our study sheds light on the effects of a space-time-dependent velocity field on electron fluids and paves the way for exploring quantum materials using new probes and perturbations.