Enhanced lifetimes of spin chains coupled to chiral edge states

Abstract

We consider spin relaxation of finite-size spin chains exchanged coupled with a one-dimensional (1D) electron gas at the edge of a quantum spin Hall (QSH) insulator. Spin lifetimes can be enhanced due to two independent mechanisms. First, the suppression of spin-flip forward scattering inherent in the spin momentum locking of the QSH edges. Second, the reduction of spin-flip backward scattering due to destructive interference of the quasiparticle exchange, modulated by k F d, where d is the inter-spin distance and k F is the Fermi wavenumber of the electron gas. We show that the spin lifetime of the S=1/2 ground state of odd-numbered chains of antiferromagnetically coupled S=1/2 spins can be increased more than 4 orders of magnitude by properly tuning the product k F d and the spin size N, in strong contrast with the 1D case. Possible physical realizations together with some potential issues are also discussed.

Electrically detected single-spin resonance with quantum spin Hall edge states

“…In other words, the magnitude of the maximal current is determined by T 1 provided 2 T 1 T 2 1. In this limit, the spin relaxation rate due to the Kondo exchange for a single S = 1/2 spin interacting with the spin-locked edge of a QSHI is given by [36] 1…”

“…The interplay between local spins and the spin-locked edge states of a QSHI has been widely studied theoretically [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Several physical realizations of the local spin have been considered, including a confined electron in a quantum dot [29,35], nanomagnets [28], magnetic atoms [26,27], spin chains [36], nuclear spins [25,33,37], and magnetic molecules [32]. Early works focused on the Kondo effect [21,24], and the influence of magnetic impurities on conductance [22].…”

“…We label P 0 and P 1 as the probabilities of occupying the ground (0) and excited (1) states, respectively. The relevant spin-exchange process that gives place to spin flips is governed by the Hamiltonian [36]…”

Electrically-detected single-spin resonance with Quantum Spin Hall edge states

“…The interplay between local spins and the spin-locked edge states of a QSHI has been widely studied theoretically [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] . Several physical realizations of the local spin have been considered, including a confined electron in a quantum dot 29,35 , nanomagnets, 28 magnetic atoms, 26,27 spin chains 36 , nuclear spins, 25,33,37 and magnetic molecules 32 . Early works focused on the Kondo effect, 21,24 and the influence of magnetic impurities on conductance 22 .…”