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

K F Yang,Y Hirayama,K Nagase,M B Santos,H W Liu,M M Uddin,Z N Yang,T D Mishima

doi:10.1088/1367-2630/ab34ce

Abstract

The nuclear spin-lattice relaxation time T1 of the ν = 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 ν = 1 that possesses a Korringa-type temperature dependence, the temperature-independent short T1 of the ν = 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.

Highlights

The quantum Hall ferromagnet (QHF) formed at two energetically-degenerate spin-resolved Landau levels (LLs) in a two-dimensional electron gas (2DEG) has provided an ideal system for understanding itinerant electron ferromagnetism, spin interactions, and domain dynamics [1,2,3,4,5,6,7,8,9,10,11,12,13]
A resistively detected nuclear magnetic resonance (RDNMR) technique developed in the QHF of GaAs 2DEGs at filling factor = 2/3 (corresponding to a composite-fermion (CF) filling factor CF = 2) has been widely used to investigate the dynamic nuclear polarization (DNP) in semiconductors [14, 15], to coherently control the nuclear spins in the 2DEG [16], and to discover exotic electron phases in quantum Hall systems [17,18,19]
Our preliminary results show that T1 in this QHF is independent of temperature (T), it is unclear whether such a T1 property is unique or not because the T1 measurement of the non-QHF states by means of a pump-probe technique is not available due to the difficulty in fabricating the InSb 2DEG with gate control

Summary

Introduction

The quantum Hall ferromagnet (QHF) formed at two energetically-degenerate spin-resolved Landau levels (LLs) in a two-dimensional electron gas (2DEG) has provided an ideal system for understanding itinerant electron ferromagnetism, spin interactions, and domain dynamics [1,2,3,4,5,6,7,8,9,10,11,12,13]. A resistively detected nuclear magnetic resonance (RDNMR) technique developed in the QHF of GaAs 2DEGs at filling factor = 2/3 (corresponding to a composite-fermion (CF) filling factor CF = 2) has been widely used to investigate the dynamic nuclear polarization (DNP) in semiconductors [14, 15], to coherently control the nuclear spins in the 2DEG [16], and to discover exotic electron phases in quantum Hall systems [17,18,19] This highly-sensitive technique combined with the nuclear spin-lattice relaxation time T1 measurement [7, 8] as a unique probe of low-frequency spin fluctuations can be applied to investigate the domain-wall (DW) structures of the QHF that are still poorly characterized, which will lead to a more comprehensive understanding of the QHF. With our recent success in the fabrication of the gate-controlled InSb

Samples and methods

Experimental results and discussion

Conclusions