arXiv subjects

Jiahao Shentu

Publications and source records attributed to Jiahao Shentu.

4 recordsLinked to original sources

arXiv2026

Spin-group theory on Edelstein effect and spin-orbit torque in Collinear Ferromagnets

Current-induced spin-orbit torques (SOTs) are central to the electrical manipulation of magnetic order in spintronic devices. In transition-metal/collinear ferromagnet bilayers, field-like and damping-like torques have been described only phenomenologically via the spin or orbital Hall effect, lacking a rigorous symmetry-based foundation. The precise role of spin-orbit coupling (SOC) in both the Edelstein effect and SOTs has remained unresolved. Here we develop a spin-group symmetry theory for the Edelstein effect and SOTs in collinear ferromagnets, treating SOC as a symmetry-breaking perturbation. For 4mm (C4v) point group symmetry, we derive the full forms of field-like and damping-like torques, which arise predominantly from first- and second-order SOC. We further show that SOTs in both orbital-Hall-dominated Ti/Ni and spin-Hall-dominated Pt/CoFe bilayers originate at first-order SOC. Taking the 3m (C3v) torque as a paradigmatic example, we elucidate the role of second- and higher-order SOC torques in field-free switching of perpendicular magnetic anisotropy. Remarkably, in PtMnSb, we demonstrate that SOTs under certain point group symmetries deviate from the conventional form: zeroth- and first-order SOC contributions vanish identically, with the leading SOT emerging at second order. All symmetry-based predictions from spin-group theory are in excellent quantitative agreement with first-principles calculations. Our work establishes a unified symmetry framework for the microscopic understanding of the Edelstein effect and current-induced spin torques in ferromagnetic systems.

cond-mat.mtrl-sci↗

arXiv2026

Spin Hall Effect in Collinear Ferromagnets from Spin-Group Symmetry

Magnetic materials support both time-reversal-even (T-even) and time-reversal-odd (T-odd) spin Hall currents, yet their underlying microscopic origins remain elusive. Here, we elucidate the spin Hall effect (SHE) in collinear ferromagnets by treating spin-orbit coupling (SOC) as a perturbation that breaks spin-group symmetry, thereby revealing how magnetic order activates distinct spin Hall response. To first order in SOC, we identify two dominant T-even SHE mechanisms: a magnetization-independent conventional contribution and a magnetization-dependent channel associated with anomalous Hall charge transport. At the same order, the leading T-odd magnetic spin Hall effect (MSHE) originates from the exchange interaction between the conventional spin current and the local magnetization. At second order in SOC, we further uncover a distinct T-odd planar spin Hall mechanism. Our spin-symmetry analysis is corroborated by first-principles calculations, which reveal a pronounced anisotropic magnetic spin Hall effect whose magnitude can be comparable to the T-even spin Hall conductivity (SHC) when the magnetic moment is tilted away from the principal crystallographic axes. These findings clarify the microscopic origins of the SHC in collinear ferromagnets and pave the way for ferromagnet-based spin current sources with versatile properties in spintronic applications.

cond-mat.mes-hall↗

arXiv2025

Spin-orbit torques in bulk collinear antiferromagnets:complete classifications and the induced spin dynamics

Electric field induced spin-orbit torques are the crucial mechanism for electric regulations of antiferromagnetic order. However, the spin-orbit torques in antiferromagnets and the induced spin dynamics remain largely unexplored. In this work, the full classifications of SOTs in bulk collinear AFMs have been achieved based on magnetic point group. Dependent on the symmetries connecting the opposite spin sublattices, the SOTs are classified into six distinct types. Among them, the SOTs and the induced Neel vector dynamics in three representative AFMs have been investigated, where the spin sublattices are connected by fractional translation, spatial inversion, and neither by translation nor inversion symmetry respectively. The SOTs on spin sublattices have been calculated by first-principles calculations based on Kubo linear response theory, and then the induced spin dynamics are simulated by LLG equations. In typical PT symmetric AFM and the inversion symmetry breaking altermagnet, the simulations indicate that the deterministic switching of Neel vectors can be driven by field like torques. What's more, the fully electric writing of multiple antiferromagnetic domains into single domain state with preset Neel vector direction and 180 deterministic switching may also be realized. Our work may shed light on the current control of antiferromagnetic orders in collinear AFMs. Especially, for inversion symmetry breaking altermagnet, the electric writing and reading of Neel vector are highly desirable for antiferromagnetic memory applications.

cond-mat.mtrl-sci↗

arXiv2025

Longitudinal transport spin polarization of spin degenerate antiferromagnets

A vital goal in spintronics is the efficient electrical generation of spin currents, a pursuit that has recently focused on using antiferromagnets (AFMs) as spin current sources. It has been demonstrated that antiferromagnets with broken PT symmetry (parity + time reversal) can efficiently generate longitudinal and transverse spin currents. At the same time, it has been generally thought that antiferromagnets with PT symmetry (PT-AFMs) forbid the longitudinal spin polarization due to their spin-degenerate band structure. Here, in contrast to this common expectation, we show, using theoretical analysis based on magnetic point group symmetry, that most PT-AFMs can generate longitudinal spin currents due to spin-orbit coupling. Using density-functional theory, we calculate the longitudinal spin conductivity of representative PT-AFMs, L10-MnPt and Mn2Au, and show that its magnitude is comparable to that of their PT-broken counterparts. Our symmetry-enabled classification of antiferromagnets and theoretical results for the longitudinal spin conductivity in representative PT-AFMs expands our understanding of spin transport and shows the possibility of robust spin-current generation in a broad range of spin-degenerate antiferromagnets.

cond-mat.mtrl-sci↗