Analytical and numerical study of the out-of-equilibrium current through a helical edge coupled to a magnetic impurity

Article

关键词: RENORMALIZATION-GROUP METHOD;    QUANTUM;    TRANSPORT;    STATE;   

DOI  :  10.1103/PhysRevB.101.165112

来源: SCIE

【 摘 要 】

We study the conductance of a time-reversal-symmetric helical electronic edge coupled antiferromagnetically to a magnetic impurity, employing analytical and numerical approaches. The impurity can reduce the perfect conductance G(0) of a noninteracting helical edge by generating a backscattered current. The backscattered steady-state current tends to vanish below the Kondo temperature T-K for time-reversal-symmetric setups. We show that the central role in maintaining the perfect conductance is played by a global U(1) symmetry. This symmetry can be broken by an anisotropic exchange coupling of the helical modes to the local impurity. Such anisotropy, in general, dynamically vanishes during the renormalization group (RG) flow to the strong-coupling limit at low temperatures. The role of the anisotropic exchange coupling is further studied using the time-dependent numerical renormalization group method, uniquely suitable for calculating out-of-equilibrium observables of strongly correlated setups. We investigate the role of finite-bias voltage and temperature in cutting the RG flow before the isotropic strong-coupling fixed point is reached, and extract the relevant energy scales and the manner in which the crossover from the weakly interacting regime to the strong-coupling backscattering-free screened regime is manifested. Most notably, we find that at low temperatures the conductance of the backscattering current follows a power-law behavior G similar to (T/T-K)(2), which we understand as a strong nonlinear effect due to time-reversal-symmetry breaking by the finite bias.

【 授权许可】

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