Spin and charge transports with thermodynamic electron–hole correlation in nearly compensated metals

The long spin-relaxation time (τs) toward the large transport distance of spin current (SC) is desirable for practical applications of spintronic devices because spatially and temporally large spin coherence makes spin manipulation easier. Here, we propose that nearly compensated metals (CMs) with electron–hole collisions accompanied by spin flipping have a potential mechanism that makes τs associated with the antiparallel SC extraordinarily long, where antiparallel SC is defined as the vector subtraction of hole and electron SCs. The present theoretical study on spin and charge transports in nearly CMs shows that (i) it is antiparallel SC that satisfies the Onsager reciprocal relation in combination with conventional charge current, (ii) both longitudinal and Hall resistivities are influenced by the enhancement of τs and are classified into two specific mechanisms, i.e., the conventional and the resonance Hall effect accompanied by a sustaining mode of antiparallel SC, and (iii) the resonance Hall effect is not influenced by the spin–orbit interaction unlike the non-resonance case. These findings indicate the potential of nearly CMs in application of spintronic materials.