Tunable Charge and Spin Seebeck Effects in Magnetic Molecular Junctions

TL;DR

This paper investigates how magnetic anisotropy, magnetic fields, and temperature influence charge and spin Seebeck effects in a spin-1 molecular junction, revealing tunable thermoelectric properties with potential applications.

Contribution

It demonstrates the tunability of charge and spin Seebeck effects in magnetic molecular junctions through magnetic anisotropy and external magnetic fields, using numerical renormalization group analysis.

Findings

Large charge Seebeck coefficient enhancement with magnetic anisotropy.

High sensitivity of spin Seebeck effect to magnetic fields in the Kondo regime.

Similar effects observed in C60 junctions with singlet-triplet gap control.

Abstract

We study the charge and spin Seebeck effects in a spin-1 molecular junction as a function of temperature (T), applied magnetic field (H), and magnetic anisotropy (D) using Wilson's numerical renormalization group. A hard-axis magnetic anisotropy produces a large enhancement of the charge Seebeck coefficient Sc (\sim k_B/|e|) whose value only depends on the residual interaction between quasiparticles in the low temperature Fermi-liquid regime. In the underscreened spin-1 Kondo regime, the high sensitivity of the system to magnetic fields makes it possible to observe a sizable value for the spin Seebeck coefficient even for magnetic fields much smaller than the Kondo temperature. Similar effects can be obtain in C60 junctions where the control parameter is the gap between a singlet and a triplet molecular state.