Layer-locked multiple valley Hall effects in tetragonal altermagnetic/ferromagnetic monolayers <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>M</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mi>SiC</mml:mi> <mml:msub> <mml:mi>X</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>M</mml:mi> <mml:mo>=</mml:mo> <mml:mtext>transition metal</mml:mtext> <mml:mo>;</mml:mo> <mml:mo> </mml:mo> <mml:mi>X</mml:mi> <mml:mo>=</mml:mo> <mml:mi mathvariant="normal">S</mml:mi> <mml:mo>,</mml:mo> <mml:mo> </mml:mo> <mml:mi>Se</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> </mml:math>
Hongxin Chen, Fanzheng Chen, H. Cheng, Xiuwen Zhao, Guichao Hu, Xiaobo Yuan, Junfeng Ren
Abstract
Exploring valley physics in materials with nonhexagonal crystal structures is a promising avenue for advancing two-dimensional valleytronics. The valley-related Hall effect enables precise electron control by manipulating the valley degree of freedom. Here, we explore the operability of layer-locked multiple valley Hall effects (VHEs) realized in tetragonal altermagnetic/ferromagnetic monolayers ${M}_{2}\mathrm{SiC}{X}_{2}$ (M is a transition metal atom; $X=\mathrm{S}, \mathrm{Se}$). Using tetragonal monolayers ${\mathrm{Cr}}_{2}\mathrm{SiC}{X}_{2}$ as examples, we examine their collinear altermagnetic trivial state and collinear ferromagnetic nontrivial state through first-principles calculations. The net layer-locked VHE and anomalous dual VHE arise from valley-layer coupling, nonzero Berry curvature, and spin splitting. Additionally, the net layer-locked anomalous VHE can also be realized and switched by applying a vertical external electric field or uniaxial strain. Our results provide a platform for layer-locked multiple VHEs and highlight the potential of these materials in low-power-consumption spin valleytronic devices.