Triplon current generation in solids

TL;DR

This paper reports the experimental detection of a triplon spin Seebeck effect in a spin-Peierls system, demonstrating triplon-mediated spin current generation driven by thermal gradients, which is a novel finding in quantum dimerized spin systems.

Contribution

First experimental observation of a triplon spin Seebeck effect, revealing triplon transport as a mechanism for spin current generation in quantum spin systems.

Findings

Triplon spin Seebeck effect observed in CuGeO₃.

Triplon spin current sign is opposite to spin-wave cases.

Effect persists below the spin-Peierls transition temperature.

Abstract

A triplon refers to a fictitious particle that carries angular momentum $S = 1$ corresponding to the elementary excitation in a broad class of quantum dimerized spin systems. Such systems without magnetic order have long been studied as a testing ground for quantum properties of spins. Although triplons have been found to play a central role in thermal and magnetic properties in dimerized magnets with singlet correlation, a spin angular momentum flow carried by triplons, a triplon current, has not been detected yet. Here we report spin Seebeck effects induced by a triplon current: triplon spin Seebeck effect, using a spin-Peierls system CuGeO$_3$. The result shows that the heating-driven triplon transport induces spin current whose sign is positive, opposite to the spin-wave cases in magnets. The triplon spin Seebeck effect persists far below the spin-Peierls transition temperature, being consistent with a theoretical calculation for triplon spin Seebeck effects.