Tomoaki Kameda is a Ph.D. student at Kwansei Gakuin University and a Junior Researcher at the National Institute for Materials Science (NIMS), Japan. His research focuses on theoretical condensed matter physics and electronic transport in two-dimensional materials. His current research focuses on spin-current generation and nonlinear transport phenomena in Janus transition-metal dichalcogenides.

Two-dimensional transition metal dichalcogenides (TMDCs) provide a versatile platform for controlling spin and charge transport through crystal-symmetry engineering and spin–orbit coupling (SOC) [1]. In Janus TMDCs [2], inequivalent top and bottom chalcogen layers break the out-of-plane mirror symmetry and generate an internal electric field, leading to Rashba-type SOC. Here, we theoretically investigate linear spin and nonlinear charge transport in Janus TMDCs. For monolayer 1H-WSeTe, a tight-binding model shows that linearly polarized light can generate pure spin Hall currents (Fig. 1), and Rashba SOC plays a key role in determining the spin-polarization direction and enhancing the spin-current response [3]. We further study nonlinear transport in 1T′-Janus TMDCs (Fig. 2). While crystal symmetries suppress the Berry-curvature dipole in pristine systems, Janus-induced symmetry breaking allows a finite Berry-curvature dipole, resulting in a nonlinear Hall charge current without external strain. These results demonstrate that Janus engineering provides a route to control distinct spin and charge responses through symmetry breaking and band geometry, offering design principles for low-dimensional spintronic and nonlinear electronic devices.

1. S. Manzeli and A. Kis. et.al. Nat. Rev. Mater. 2, 17033 (2017). DOI: 10.1038/natrevmats.2017.33
2. J. Zhang et al. ACS Nano 11, 8192–8198 (2017). DOI: 10.1021/acsnano.7b03186
3. T. Kameda, K. Wakabayashi, Phys. Rev. B 111, 195425 (2025). DOI: 10.1103/PhysRevB.111.195425