Scalar Spin Chirality from Dissipative Pumping and Lamb-Shift Precession

Abstract

How electrical driving generates and reverses scalar spin chirality in an interacting system with a real Hamiltonian and no magnetic flux remains a fundamental open question. We show that dissipative tunneling prepares an orbital pseudospin, while virtual charge fluctuations generate a noncollinear Lamb field that rotates it toward the chiral direction. Bias changes their relative orientation and thereby reverses the current. This reservoir-induced orbital Hanle effect converts a nonchiral orbital polarization into scalar spin chirality. Within the ground-state space, the circulating current is determined by the scalar spin chirality. Hierarchical-equations-of-motion calculations show that the low-bias reversal survives beyond the second-order weak-coupling description, while the quadratic growth of chirality after a sudden voltage switch identifies precession. More broadly, time-reversal-odd responses can emerge in open quantum systems from the interplay between dissipative state preparation and coherent precession.