An Autonomous Topological Pump

TL;DR

This paper proposes an autonomous topological quantum pump where a quantum spin's Larmor precession induces quantized fermion transport without external control, demonstrating robustness above a critical magnetic field.

Contribution

It introduces a self-contained topological pump using a quantum spin to replace external control parameters, enabling autonomous quantized particle transport.

Findings

The spin's Larmor precession drives topologically quantized fermion transport.

A critical magnetic field value ensures the robustness of the autonomous pump.

Numerical evidence shows the pump's topological protection depends on the magnetic field strength.

Abstract

Robust quantization of particle transport, as in a Thouless pump, is a hallmark of topological quantum systems with externally controlled system parameters. Here we instead propose and analyze a Thouless pump, for fermions in a one-dimensional lattice, in which external control is not needed, because an additional dynamical degree of freedom allows the pump to work autonomously. The external control parameters are replaced by a quantum spin in a static magnetic field, so that Larmor precession of the spin performs the control cycle that induces topologically quantized transport of the fermions -- at least in some higher energy eigenstates of the combined system. In other states, the back-action of the fermions on the spin can distort the control cycle enough to disrupt the transport, but we find numerical evidence for a critical value of the magnetic field above which the autonomous pump works with topological robustness, suggesting that topological protection and autonomous operation together may permit robust "quantum motors".