Influence of parallel magnetic fields on a single-layer two-dimensional electron system with a hopping mechanism of conductivity

TL;DR

This paper investigates how parallel magnetic fields influence the magnetoresistance and conductivity mechanisms in a 2D electron system with hopping conduction, highlighting the role of spin interactions and Hubbard band states.

Contribution

It demonstrates the significant impact of parallel magnetic fields on 2D VRH conductivity and proposes a spin-related hopping mechanism involving double occupied states.

Findings

Large positive magnetoresistance observed in strong parallel magnetic fields.

Change in temperature dependence of conductivity indicates spin involvement.

Orbital effects are not relevant to the observed magnetoresistance.

Abstract

Large positive (P) magnetoresistance (MR) has been observed in parallel magnetic fields in a single 2D layer in a delta-doped GaAs/AlGaAs heterostructure with a variable-range-hopping (VRH) mechanism of conductivity. Effect of large PMR is accompanied in strong magnetic fields by a substantial change in the character of the temperature dependence of the conductivity. This implies that spins play an important role in 2D VRH conductivity because the processes of orbital origin are not relevant to the observed effect. A possible explanation involves hopping via double occupied states in the upper Hubbard band, where the intra-state correlation of spins is important.