Robust $d$-wave altermagnetism in $\mathrm{RbCr_2Se_2O}$

Abstract

The $\mathrm{KV_2Se_2O}$, $\mathrm{Rb_{1-δ}V_2Te_2O}$ and $\mathrm{Cs_{1-δ}V_2Te_2O}$ are experimentally confirmed to adopt either C-type or G-type antiferromagnetic configuration, corresponding to apparent or hidden altermagnetism. However, their nearly degenerate energies lead to inconsistent experimental assignments between the two antiferromagnetic configurations. Here, we predict that the experimentally synthesized $\mathrm{RbCr_2Se_2O}$ is a robust $d$-wave altermagnetic metal, since the energy difference between C-type and G-type configurations is large, which is independent of electron correlation strength and van der Waals interaction. Upon applying in-plane uniaxial strain, $\mathrm{RbCr_2Se_2O}$ can generate a net total magnetic moment via a direct piezomagnetic effect, which is distinct from semiconductor that typically requires carrier doping in addition to strain. This provides an experimental strategy for distinguishing the G-type antiferromagnetic configuration, in which the total magnetic moment remains zero under uniaxial strain. Our work presents an isostructural $d$-wave altermagnetic $\mathrm{RbCr_2Se_2O}$ analogous to $\mathrm{KV_2Se_2O}$, $\mathrm{Rb_{1-δ}V_2Te_2O}$ and $\mathrm{Cs_{1-δ}V_2Te_2O}$, which can facilitate further experimental verification. Furthermore, these results are universal across materials of this family $\mathrm{XCr_2Y_2O}$ (X=K, Rb, Cs; Y=Se, Te), thus expanding the family of altermagnets.

Figures (5)

• Figure 1: (Color online) For $\mathrm{RbCr_2Se_2O}$, (a): the crystal structure with blue, red, green and gray spheres representing Cr, O, Se and Rb atoms, respectively. The black box denotes the magnetic primitive cell. (b): four possible magnetic configurations with F-type, A-type, C-type and G-type. (c): the energies (per magnetic primitive cell) of F-, A-, and G-type configurations as functions of $U$, with C-type set to zero. (d): the global energy band structure with C-type AFM configuration at $U$=0.00, 1.00, 2.00 and 3.00 eV. The blue, red, and purple curves denote the spin-up, spin-down, and spin-degenerate bands, respectively.
• Figure 2: (Color online) For $\mathrm{RbCr_2Se_2O}$ without uniaxial strain at $U$=0.00 eV, the energy band structures with spin-resolved projections onto the sector A (a) and sector B (b) with C-type AFM configuration. The blue, red, and purple denote the spin-up, spin-down, and spin-degenerate bands, and the weighting coefficient is proportional to the circle size.
• Figure 3: (Color online) For $\mathrm{RbCr_2Se_2O}$, the global energy band structure with C-type AFM configuration at $a/a_0$=0.96 (a), 0.98 (b), 1.00 (c), 1.02 (d) and 1.04 (e). The blue, red, and purple curves denote the spin-up, spin-down, and spin-degenerate bands, respectively.
• Figure 4: (Color online) For $\mathrm{RbCr_2Se_2O}$, (a): the energy (per magnetic primitive cell) of G-type configuration as function of $a/a_0$ with C-type set to zero. (b): the total magnetic moment as a function of $a/a_0$ with C-type and G-type AFM configurations.
• Figure 5: (Color online) For $\mathrm{KCr_2Se_2O}$ (a), $\mathrm{RbCr_2Se_2O}$ (b), $\mathrm{CsCr_2Se_2O}$ (c), $\mathrm{KCr_2Te_2O}$ (d), $\mathrm{RbCr_2Te_2O}$ (e) and $\mathrm{CsCr_2Te_2O}$ (f), (A): the energy (per magnetic primitive cell) of G-type configuration as function of $U$ with C-type set to zero, and the total magnetic moment as a function of $a/a_0$ with C-type; (B): the global energy band structure with C-type, and the blue, red, and purple curves denote the spin-up, spin-down, and spin-degenerate bands, respectively.