Enhancing intrinsic spin Hall effect: insights into chiral crystals and topological materials

This review presents a comprehensive analysis of recent advances in enhancing the intrinsic spin Hall effect (SHE) in emergent quantum materials, including chiral crystals and topological materials, by leveraging their shared symmetry-breaking features and spin-orbit coupling (SOC)-driven phenomena. The SHE, a transformative mechanism for magnetic-field-free charge-to-spin interconversion, lies at the heart of energy-efficient spintronics. Chiral crystals, with their inherent structural handedness and broken inversion symmetry, synergize with topological materials-such as Weyl semimetals and insulators-to amplify SHE through distinct yet complementary mechanisms. These include chiral spin textures, Weyl/Dirac fermions, band-inversion-induced Berry curvature hotspots, and protected surface or hinge states, all governed by strong SOC and unique spin-momentum locking. We systematically analyze how the interplay of symmetry, topology, and electronic structure in these materials creates unprecedented opportunities for SHE enhancement, supported by breakthroughs in computational design (e.g. ab initio Berry curvature engineering) and experimental strategies such as strain, alloying, and heterostructuring. Critical challenges, including the SOC-diffusion length trade-off and the need to harness magnetic or low-symmetry phases, are discussed in the context of material optimization. By unifying insights from chiral and topological systems, this review charts a roadmap for transcending conventional spin current generation paradigms and advancing scalable spintronic technologies.