Spin thermopower in the overscreened Kondo model

TL;DR

This paper investigates how magnetic fields influence the spin thermopower in the overscreened two-channel Kondo model, revealing a characteristic saturation and proposing a method to distinguish different quantum regimes in nanodevices.

Contribution

It demonstrates the impact of magnetic fields on the spectral function and spin thermopower in the overscreened Kondo model, highlighting a measurable signature of non-Fermi-liquid behavior.

Findings

Spin thermopower saturates at 0.388kB/|e| at T ~ T*

Magnetic field affects the spectral function without strongly polarizing the impurity spin

Measurement of spin thermopower can distinguish Fermi liquid from non-Fermi-liquid regimes

Abstract

We study the spin thermopower in the two-channel spin-1/2 Kondo model which exhibits the phenomenon of impurity spin overscreening and non-Fermi-liquid properties. While magnetic field lower than the Kondo temperature does not strongly polarize the impurity spin, we show that it nevertheless strongly affects the low-energy part of the spectral function. In turn, this leads to characteristic saturation of the spin Seebeck coefficient at the value of 0.388kB/|e| at T ~ T*, where T* ~ B^2/TK is the scale of the crossover between the intermediate-temperature non-Fermi-liquid regime and the low-temperature Fermi-liquid regime. We show that measuring the spin thermopower at low magnetic fields would provide a sensitive test for distinguishing regular Fermi liquid, singular Fermi liguid, and non-Fermi liquid behaviour in nanodevices.