Unusual spin dynamics in topological insulators

Abstract

The dynamic spin susceptibility (DSS) has a ubiquitous Lorentzian form in conventional materials with weak spin orbit coupling, whose spectral width characterizes the spin relaxation rate. We show that DSS has an unusual non-Lorentzian form in topological insulators, which are characterized by strong SOC. At zero temperature, the high frequency part of DSS is universal and increases in certain directions as ${\omega }^{d-1}$ with $d=2$ and 3 for surface states and Weyl semimetals, respectively, while for helical edge states, the interactions renormalize the exponent as $d=2K-1$ with $K$ the Luttinger-liquid parameter. As a result, spin relaxation rate cannot be deduced from the DSS in contrast to the case of usual metals, which follows from the strongly entangled spin and charge degrees of freedom in these systems. These parallel with the optical conductivity of neutral graphene.

5 pages, 3 figures

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Cited by in corpus (4)

• Kubo formula for non-Hermitian systems and tachyon optical conductivity
• Spin-relaxation time in materials with broken inversion symmetry and large spin-orbit coupling
• Spin dynamics of $3d$ and $4d$ impurities embedded in prototypical topological insulators
• Minimum entropy production effect on a quantum scale