Spin Seebeck Effect of Triangular-lattice Spin Supersolid

TL;DR

This paper investigates the spin Seebeck effect in a triangular-lattice quantum antiferromagnet with a spin supersolid phase, revealing unique low-temperature spin current behaviors and establishing spin supersolids as promising platforms for spin caloritronics.

Contribution

It introduces the first detailed analysis of the spin Seebeck effect in spin supersolid phases, highlighting the role of frustration and Goldstone modes in quantum spin transport.

Findings

Negative spin current persists in the spin supersolid phase.

Distinct temperature dependence of spin current reveals different spin states.

Universal scaling behavior at quantum critical points.

Abstract

Using thermal tensor-network approach, we investigate the spin Seebeck effect (SSE) of the triangular-lattice quantum antiferromagnet hosting spin supersolid phase. We focus on the low-temperature scaling behaviors of the normalized spin current across the interface. For the 1D Heisenberg chain, we find a negative spinon spin in the bulk current with algebraic temperature scaling; at low fields, boundary effects induce a second sign reversal at lower temperatures. These benchmark results are consistent with field-theoretical analysis. On the triangular lattice, spin frustration dramatically enhances the low-temperature SSE, with distinct spin-current signatures -- particularly the sign reversal and characteristic temperature dependence -- distinguishing different spin states. Remarkably, we discover a persistent, negative spin current in the spin supersolid phase, which saturates to a non-zero value in the low-temperature limit and can be ascribed to the Goldstone-mode-mediated spin supercurrents. Moreover, a universal scaling $T^{d/z}$ is found at the U(1)-symmetric polarization quantum critical points. These distinct quantum spin transport traits provide sensitive spin current probes for spin supersolid states in quantum magnets such as Na$_2$BaCo(PO$_4$)$_2$. Furthermore, our results also establish spin supersolids as a tunable quantum platform for spin caloritronics in the ultralow-temperature regime.