Feng-Ren Fan

Hidden altermagnetism was theoretically proposed and then experimentally confirmed in the metal ${\mathrm{Cs}}_{1\ensuremath{-}\ensuremath{\delta}}{\mathrm{V}}_{2}{\mathrm{Te}}_{2}\mathrm{O}$, which exhibits two nearly degenerate ground-state magnetic configurations ($C$ type and $G$ type), corresponding, respectively, to apparent and hidden altermagnetism. Here, we propose that in-plane uniaxial strain can be utilized to distinguish apparent and hidden altermagnetism. Under uniaxial strain, apparent altermagnetism exhibits an obvious net magnetic moment, whereas hidden altermagnetism maintains zero net magnetic moment. The magnetic moment induced by uniaxial strain here, namely, the piezomagnetic effect, differs from that in semiconductors, where strain must be applied first, followed by carrier doping, to generate net magnetism. First-principles calculations verify our proposal, revealing that the magnetic moment induced by uniaxial strain in $C$-type antiferromagnetic ${\mathrm{CsV}}_{2}{\mathrm{Te}}_{2}\mathrm{O}$ is much larger than that in previously studied altermagnetic semiconductors. Furthermore, we also investigate the electronic state transitions of semiconductors featuring a crystal structure analogous to ${\mathrm{CsV}}_{2}{\mathrm{Te}}_{2}\mathrm{O}$ under uniaxial strain and verify our proposal for specific materials via first-principles calculations. Upon application of uniaxial strain, $C$-type ${\mathrm{CsV}}_{2}{\mathrm{Te}}_{2}\mathrm{O}$ exhibits the anomalous Hall effect via the piezomagnetic effect, while $G$-type ${\mathrm{CsV}}_{2}{\mathrm{Te}}_{2}\mathrm{O}$ shows no anomalous Hall response. Our work provides an experimentally feasible strategy to distinguish apparent and hidden altermagnetism in the ${\mathrm{CsV}}_{2}{\mathrm{Te}}_{2}\mathrm{O}$ family.