Inhomogeneous nuclear spin polarization induced by helicity-modulated optical excitation of fluorine-bound electron spins in ZnSe

TL;DR

This study demonstrates inhomogeneous nuclear spin polarization in fluorine-doped ZnSe induced by helicity-modulated optical excitation, revealing spatial inhomogeneity and resonance effects linked to nuclear magnetic resonance of isotopes.

Contribution

It introduces a novel mechanism of optically-induced nuclear spin polarization based on resonant nuclear spin cooling driven by inhomogeneous Knight fields.

Findings

Nuclear spin polarization exhibits a dispersion-like shape with resonances at isotope NMR fields.

The polarization is spatially inhomogeneous near fluorine donors.

Resonant nuclear spin cooling mechanism is proposed.

Abstract

Optically-induced nuclear spin polarization in a fluorine-doped ZnSe epilayer is studied by time-resolved Kerr rotation using resonant excitation of donor-bound excitons. Excitation with helicity-modulated laser pulses results in a transverse nuclear spin polarization, which is detected as a change of the Larmor precession frequency of the donor-bound electron spins. The frequency shift in dependence on the transverse magnetic field exhibits a pronounced dispersion-like shape with resonances at the fields of nuclear magnetic resonance of the constituent zinc and selenium isotopes. It is studied as a function of external parameters, particularly of constant and radio frequency external magnetic fields. The width of the resonance and its shape indicate a strong spatial inhomogeneity of the nuclear spin polarization in the vicinity of a fluorine donor. A mechanism of optically-induced nuclear spin polarization is suggested based on the concept of resonant nuclear spin cooling driven by the inhomogeneous Knight field of the donor-bound electron.