Multitudes of Stable States in a Periodically Driven Electron-Nuclear Spin System in a Quantum Dot

TL;DR

This paper demonstrates that a quantum dot electron-nuclear spin system can exhibit numerous stable states under pulsed laser excitation, functioning as a digital frequency converter with over a hundred stable channels.

Contribution

It reveals the existence of multiple stable states in a periodically driven electron-nuclear spin system in quantum dots, expanding understanding of spin dynamics under pulsed excitation.

Findings

Multiple stable states exist in the electron-nuclear spin system.

Precession frequencies differ by multiples of the modulation frequency.

System acts as a digital frequency converter with many stable channels.

Abstract

The periodical modulation of circularly polarized light with a frequency close to the electron spin resonance frequency induces a sharp change of the single electron spin orientation. Hyperfine interaction provides a feedback, thus fixing the precession frequency of the electron spin in the external and the Overhauser field near the modulation frequency. The nuclear polarization is bidirectional and the electron-nuclear spin system (ENSS) possesses a few stable states. A similar frequency-locking effect exists for two-color and mode-locked excitations, too. However, the pulsed excitation with mode locked laser brings about the multitudes of stable states in ENSS in a quantum dot. The resulting precession frequencies of the electron spin differ in these states by the multiple of the modulation frequency. Under such conditions ENSS represents a digital frequency converter with more than a hundred stable channels.