Pump-probe nuclear spin relaxation study of the quantum Hall ferromagnet at filling factor nu = 2

TL;DR

This study investigates the nuclear spin relaxation in a quantum Hall ferromagnet at filling factor nu=2, revealing short, temperature-independent T1 times linked to domain wall excitations, advancing understanding of quantum Hall states.

Contribution

It provides the first characterization of T1 in the nu=2 quantum Hall ferromagnet using pump-probe techniques, highlighting the role of domain wall skyrmions in spin relaxation.

Findings

T1 is short and temperature-independent at nu=2.

T1 is unaffected by filling factor and current.

Results suggest low energy collective spin excitations in domain walls.

Abstract

The nuclear spin-lattice relaxation time T1 of the nu = 2 quantum Hall ferromagnet (QHF) formed in a gate-controlled InSb two-dimensional electron gas has been characterized using a pump-probe technique. In contrast to a long T1 of quantum Hall states around nu = 1 that possesses a Korringa-type temperature dependence, the temperature-independent short T1 of the nu = 2 QHF suggests the presence of low energy collective spin excitations in a domain wall. Furthermore, T1 of this ferromagnetic state is also found to be filling- and current-independent. The interpretation of these results as compared to the T1 properties of other QHFs is discussed in terms of the domain wall skyrmion, which will lead to a better understanding of the QHF.