Spin Seebeck Effect Induced by Quantum Interference in Organic Collinear Antiferromagnetic Molecular Junctions

Realizing the spin Seebeck effect (SSE) in collinear antiferromagnets remains a longstanding challenge because of their compensated spin structures and spin-degenerate electronic states. Here, using an extended Su-Schrieffer-Heeger model combined with the Green's function method, we theoretically demonstrate a giant SSE in an organic collinear antiferromagnetic heptacene molecular junction without any ferromagnetic elements. Mechanism analysis indicates that the SSE originates from spin-dependent destructive quantum interference rather than spin splitting of the molecular energy levels. This spin-dependent interference arises from the asymmetric spatial distribution of the antiferromagnetic frontier orbitals in the meta-connected junction. We also show that the electron-electron interaction is crucial for the pronounced SSE. The results are further supported by first-principles calculations. The spin thermoelectric current under a finite temperature difference and the generality of the proposed mechanism in other organic antiferromagnetic molecules are further demonstrated. These findings establish a new route to realize the SSE in conventional organic collinear antiferromagnets, and expand their potential application in spin caloritronics.