Giant spin Hall effects and topological surface states in ternary-layered MAX carbides Mn+1AlCn (M= Nb, Ta, n=1, 2, 3)

Yanhui Chen; Hong-Yan Lu; Wenjin Yang; Meifeng Liu; Bin Cui; Desheng Liu; Bing Huang; Xi Zuo

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arXiv · 2508.07061

Giant spin Hall effects and topological surface states in ternary-layered MAX carbides Mn+1AlCn (M= Nb, Ta, n=1, 2, 3)

Yanhui Chen·Hong-Yan Lu·Wenjin Yang·Meifeng Liu·Bin Cui·Desheng Liu·Bing Huang·Xi Zuo

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Abstract

In this work, we report a systematic study of the electronic structures, band topology, and intrinsic spin Hall effect (SHE) of the layered MAX carbides Mn+1AlCn (M= Nb, Ta, n=1, 2, 3) and explore the correlation effects on the SHE. The results show that M3AlC2 and M4AlC3 (M= Nb, Ta) share similar Dirac-band-crossing features near the Fermi level (EF) and form nodal lines in the absence of spin-orbit coupling (SOC). When the SOC is included, the Dirac band crossings are fully gapped, resulting in nontrivial Z2 topological invariants (1;000) with a pair of surface states on the (001) plane. Remarkably, the multiple gapped Dirac points contribute to locally strong spin Berry curvatures, which lead to large spin Hall conductivities and a giant spin Hall angle up to ~ 60% for Ta3AlC2. Moreover, we also elucidate the impact of Hubbard U correction on SHC. Our findings indicate that Ta3AlC2 might represent an intriguing layered Z2 topological metal with superior charge-to-spin conversion efficiency.

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Yanhui Chen, Hong-Yan Lu, Wenjin Yang, Meifeng Liu, Bin Cui, Desheng Liu, Bing Huang, Xi Zuo. 2025-08-09. Giant spin Hall effects and topological surface states in ternary-layered MAX carbides Mn+1AlCn (M= Nb, Ta, n=1, 2, 3). https://arxiv.org/abs/2508.07061

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