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Universal intrinsic higher-rank spin Hall effect

Spin Hall effect (SHE), a fundamental transport phenomenon with non-zero spin current but vanishing charge current, has important applications in spintronics for the electrical control of spins. Owing to the half-spin nature of electrons, the rank of spin current (determined by the rank of spin tensors) has been restricted to 0 and 1 for charge and spin Hall effects. Motivated by recent studies of pseudospin-1 fermions in solid state and cold atomic systems, here we introduce and characterize higher-rank ($\geq 2$) SHEs in large spin ($\geq 1$) systems. We find a universal rank-2 spin Hall conductivity $e/{8}π$, with zero rank-0 and 1 conductivities, for a spin-1 model with intrinsic spin-orbit coupling. Similar rank-2 SHEs can also be found in a spin-3/2 system. An experimental scheme is proposed to realize and measure rank-2 SHEs with pseudospin-1 ultracold fermionic atoms. Our results reveal novel spin transport phenomena in large spin systems and may find important applications in designing innovative spintronic devices.