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Page 2 of 13 Ashani et al. Energy Mater. 2025, 5, 500111 https://dx.doi.org/10.20517/energymater.2025.10

bands of the AM materials do not entirely overlap. Rather, the band structure exhibits
orientational-dependent splitting. The spin-orbit coupling (SOC)-induced magnetic property has been the
cornerstone of spintronic applications such as spin-orbit torque, spin transistors, topological insulators, and
[2,3]
the spin Hall effect . Nevertheless, the swift decoherence of spin-polarized electrons caused by SOC
restricts the broad applications of these materials . In contrast, spin splitting has been achieved in AM
[4]
[5-7]
materials without applying SOC . The source of the spin splitting in AM materials is the magnetic space
group, which is protected by crystal symmetry . This spin-splitting allows the realization of highly
[8,9]
spin-polarized currents [8,10] . The study of AM materials is still in its infancy; however, it may be a fertile field
for theory and potential applications. For example, the unique band feature in AM materials may make
them potential materials for thermal transport devices, valleytronics, field-effect electronics,
photo-magnetism, spin caloritronics, spin transfer torque, superconductivity, and spintronic
applications [9-12] . The AM materials also have the potential for high-speed device operation because of their
ultra-high dynamic speed and zero net magnetic moment, allowing resistance to external magnetic
disturbance . Several bulk materials, such as RuO , FeSb , FeF , MnTe, Ve Te O, MnF , MnO, CoF , MnO ,
[13]
2
2
2
3
2
2
2
2
NaFeO , NdB C , and some GdFeO -type perovskites, have been predicted to be AM materials [13-16] .
2 2
2
3
In parallel with the discovery of the AM behavior in RuO and other bulk materials, it has been predicted
2
that two-dimensional (2D) materials such as Mn ClI, V S O, MnTeMoO , V F Cl, Cr SO, V SeTeO, Cr O ,
2
2 2
2
6
2
2
2
2 7
CrMoC S , Mn ClF, RuF , and Cr SeO can also display an AM behavior [4-6,17,18] . However, most studies have
2 6
4
2
2
concentrated on basic unconventional properties with minimal reports on thermoelectricity in AM
materials [19-24] . Recently, Sukhachov et al. suggested that AM materials could be employed for effective
thermoelectricity . Using the AM spin-splitting effect, Bai et al. also reported efficient spin-charge
[25]
conversion in RuO altermagnet . Besides, Lyu and Li pointed out that the transport properties in AM
[26]
2
materials were directional dependent . Indeed, the AM behavior has been experimentally confirmed in
[27]
RuO and MnTe using angle-resolved photoemission spectroscopy [28,29] . Fan et al. also reported experimental
2
work that the AM spin splitting effect could produce anisotropic spin currents in AM material with
polarization, which depends on the crystal orientation of the material . Moreover. Bai et al. also reported a
[30]
few microvolts in altermagnet RuO spin-charge conversion efficiency using spin Seebeck effect
2
[26]
measurement . Motivated by the predicted potentials of unconventional spin-splitting effect in AM
materials, we propose to leverage directional spin-dependent thermoelectric properties and predict a
massive spin-Seebeck coefficient in V S O monolayer AM material.
2 2
Indeed, thermoelectricity is a fertile field for testing and predicting high-performance transport materials
via theory-based material search techniques. Although precise prediction of these high-performance
transport materials computationally entails vigorous optimization, the experimental approach is even more
complicated. In our work, we inspect the orientational spin-dependent transport properties at finite
temperatures and aim to propose a giant spin Seebeck effect in the V S O altermagnet for the spin-polarized
2 2
current generation in spintronics and thermoelectric device applications.
THEORETICAL METHODS
All our calculations were conducted in this work using the spin-polarized density functional theory as
implemented in the Vienna ab initio simulation package (VASP) [31,32] . We used the Perdew, Burke, and
Ernzerhof parametrization within the generalized gradient approximation for an exchange functional ,
[33]
including the van der Waals interaction as a correlation functional. A plane wave basis set is employed
[34]
-3
with an energy cutoff of 600 eV. The energy and force convergence criteria are set to 10 eV and 10 eV/Å,
-6
respectively. A well-converged Monkhorst-Pack scheme-generated k-point mesh of 10 × 10 × 1, which also
ensures the convergence of the energy and force, was used . Furthermore, we applied a vacuum distance of
[35]