Distinguishing apparent and hidden altermagnetism via uniaxial strain in $\mathrm{CsV_2Te_2O}$-family

Abstract

The hidden altermagnetism has been theoretically proposed and then experimentally confirmed in metal $\mathrm{Cs_{1-δ}V_2Te_2O}$, 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 $\mathrm{CsV_2Te_2O}$ is much larger than that in the previously studied altermagnetic semiconductors. Furthermore, we also investigate the electronic state transitions of semiconductors featuring a crystal structure analogous to $\mathrm{CsV_2Te_2O}$ under uniaxial strain, and verify our proposal in specific material via first-principles calculations. Our work provides an experimentally feasible strategy to distinguish apparent and hidden altermagnetism in material $\mathrm{Cs_{1-δ}V_2Te_2O}$, and extends the physical implication of the piezomagnetic effect, which can be directly verified in experimentally synthesizable $\mathrm{KV_2Se_2O}$ and $\mathrm{Rb_{1-δ}V_2Te_2O}$.

Figures (7)

• Figure 1: (Color online) For $\mathrm{CsV_2Te_2O}$, (a): the crystal structure with blue, red, green and gray spheres representing V, O, Te and Cs atoms, respectively. The black dashed box denotes the magnetic primitive cell, which consists of sector A, sector B, and C. (b): two possible AFM configurations with C-type and G-type. (c): the schematic diagram of hidden AM electronic state, and two sectors exhibit the altermagnetism with opposite spin polarization, yet the integral cancels the spin polarization out.
• Figure 2: (Color online) For $\mathrm{CsV_2Te_2O}$, under uniaxial strain, possible electronic state transitions with C-type (a) and G-type (b) AFM configurations. Blue boxes indicate zero total magnetic moment, while red box indicates non-zero total magnetic moment. In (b), the red-colored text in parentheses represents the locally viewed electronic states.
• Figure 3: (Color online) For $\mathrm{CsV_2Te_2O}$ without uniaxial strain, the global energy band structure (a, d) along with the spin-resolved projections onto the sector A (b, e) and sector B (c, f) with C-type (a, b, c) and G-type (d, e, f) AFM configurations. The blue, red, and purple curves denote the spin-up, spin-down, and spin-degenerate bands, respectively. In (b, c, e, f), the weighting coefficient is proportional to the circle size.
• Figure 4: (Color online) For $\mathrm{CsV_2Te_2O}$ with $a/a_0$=0.98 (a, b, c, d, e, f) and 1.02 (g, h, i, j, k, l), the global energy band structure (a, d, g, j) along with the spin-resolved projections onto the sector A (b, e, h, k) and sector B (c, f, i, l) with C-type (a, b, c, g, h, i) and G-type (d, e, f, j, k, l) AFM configurations. The blue, red, and purple curves denote the spin-up, spin-down, and spin-degenerate bands, respectively. In (b, c, e, f, h, i, k, l), the weighting coefficient is proportional to the circle size.
• Figure 5: (Color online) For $\mathrm{CsV_2Te_2O}$, the total magnetic moment as a function of $a/a_0$ with C-type and G-type AFM configurations.