Anomalous spin transport in a two-channel-Kondo quantum dot device

TL;DR

This paper investigates the unusual spin transport behavior in a two-channel Kondo quantum dot device, revealing quantized conductance at low temperatures for isotropic couplings and a crossover to one-channel Kondo behavior with anisotropic couplings.

Contribution

It provides a detailed analysis of the spin conductance response in a two-channel Kondo quantum dot, highlighting the effects of coupling anisotropy and temperature on the Kondo fixed point.

Findings

Spin conductance is quantized for isotropic couplings at low T.

Anisotropic couplings lead to a crossover to one-channel Kondo behavior.

A new energy scale T_A governs the suppression of spin conductance.

Abstract

We study the response of a two-channel Kondo quantum dot device proposed by Y. Oreg and D. Goldhaber-Gordon [Phys. Rev. Lett. {\bf 90}, 136602 (2003)] to a spin-bias applied across one of its channels formed by Fermi liquid reservoirs weakly coupled to a spin-1/2 quantum dot. When the temperature $T<T_K$, the Kondo temperature of the device, the spin conductance depends on the Kondo coupling of the dot spin to the other channel in an anomalous manner. For isotropic Kondo couplings to the two channels the spin conductance is quantized for $T\ll T_K$ characterizing the two-channel Kondo fixed point. On the other hand, for anisotropic couplings a crossover energy scale $T_A\neq 0$ determines the temperature $T\ll T_A$ when the spin conductance vanishes indicating one-channel Kondo behavior.