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 current in the bulk 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 nonzero value in the low-temperature limit and can be ascribed to the Goldstone-mode-mediated spin supercurrent. 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 ${\mathrm{Na}}_2\mathrm{BaCo}({\mathrm{PO}}_4{)}_2$. Furthermore, our results also establish spin supersolids as a promising quantum platform for spin caloritronics in the ultralow-temperature regime.

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• Frustrated magnetism
• Spin Seebeck effect
• Spin dynamics
• Triangular lattice
• Heisenberg model
• Spin chains
• Spin lattice models
• Tensor network methods