Intrinsic Spin and Orbital Hall Effects in Heavy Fermion Systems

TL;DR

This paper investigates the intrinsic spin Hall effect in heavy fermion systems using a model that reveals a large, sign-dependent spin Hall conductivity driven by a spin-dependent Berry phase, independent of c-f mixing strength.

Contribution

It introduces a theoretical framework for understanding the intrinsic SHE in heavy fermion systems, highlighting the role of orbital Berry phases and providing quantitative estimates of SHC.

Findings

Intrinsic SHC in heavy fermion systems is 10 times larger than in Pt.

The sign of SHC depends on the f-electron configuration (Ce or Yb).

SHC depends only on conduction electron density, not on c-f mixing or mass enhancement.

Abstract

We study the intrinsic spin Hall effect (SHE) based on the orbitally degenerate periodic Anderson model, which is an effective model for heavy fermion systems. In the very low resistivity regime, the magnitude of the intrinsic spin Hall conductivity (SHC) is estimated as $2000 \sim 3000 \hbar e^{-1} \Omega^{-1} cm^{-1}$; It is about 10 times larger than that in Pt. Its sign is negative (positive) in Ce (Yb) compound systems with $f^1$ ($f^{13}$) configuration. Interestingly, the obtained expression for the SHC depends only on the density of conduction electrons, but is independent of the strength of the c-f mixing potential and the mass-enhancement factor. The origin of the huge SHE is the spin-dependent Berry phase induced by the complex f-orbital wavefunction, which we call the "orbital Aharonov-Bohm effect".