arXiv subjects

Daehyeon An

Publications and source records attributed to Daehyeon An.

4 recordsLinked to original sources

arXiv2026

Plaid-Like Spin Splitting and Chirality of Magnon Bands in Antiferromagnetic MnTe$_2$

Altermagnets constitute an emerging class of magnetic materials that combine compensated antiferromagnetic order with spin-split excitations arising from crystalline symmetries. Despite strong theoretical interest, their experimental identification remains challenging. Here, we demonstrate that helicity- and angle-resolved Raman scattering measurements reveal reduced rotational symmetries of magnons and a pronounced imbalance between left- and right-circular polarization channels, indicating momentum-dependent magnon handedness. First-principles DFT+$U$ calculations combined with linear spin-wave theory uncover a characteristic plaid-like spin-splitting structure in momentum space. The resulting magnon spin textures are dictated by the unconventional sublattice symmetries of MnTe$_2$ and closely emulate those of altermagnetic electronic bands. Our work provides evidence of chiral spin-wave excitations unique to this non-coplanar antiferromagnet.

cond-mat.str-el↗

arXiv2026

Consistent Evaluation of Operators Involving the Position Operator in the Bloch Representation: Application to the Orbital Moment

The position operator plays a central role in condensed-matter observables such as velocity, orbital moment, and electric polarization. In solid-state physics, the evaluation of operators incorporating the position operator has not reached a consensus, as observed in the operator-level discrepancy between the local circulation of Wannier functions and the self-rotation of wave packets. Here, to achieve a consistent evaluation of such operators, we propose three rules for evaluating operators involving the position operator in the Bloch representation. The rules are devised to satisfy physical conditions: independence from the choice of unit cell, preservation of Hermitian conjugacy for the product of operators, and recovery of the correct intraband velocity. We further address the gauge dependence of the position operator and introduce a scheme termed gauge filtration, which systematically removes gauge-dependent contributions from the operators containing the position operator. This methodology ensures that the quantities obtained from the operator evaluation correspond to observable physical phenomena. By applying our framework, we reconcile the results concerning the self-rotation of the wave packet and the local circulation of the Wannier function. We expect our proposal to establish a consistent framework for evaluating operators involving the position operator.

cond-mat.mes-hall↗

arXiv2024

Intrinsic Nernst effect of the magnon orbital moment in a honeycomb ferromagnet

The Nernst effect of the magnon orbital moment is theoretically investigated in a honeycomb ferromagnet, whose Hamiltonian contains the Heisenberg exchange, the Dzyaloshinskii-Moriya, the Kitaev, and the Zeeman interactions. More specifically, we obtain the magnon band structure, the Berry curvature, the magnon orbital moment Berry curvature, and the magnon orbital moment Nernst conductivity (MOMNC) for the Hamiltonian within the linear spin-wave theory in the polarized phase. We found the magnon orbital moment Berry curvature is largely independent of the sign of the Chern number of the band. For an experimental proposal, we estimate MOMNC of $\mathrm{CrI}_{3}$ for the Heisenberg-Kitaev-$\Gamma$-Zeeman model and Heisenberg-Dzyaloshinskii-Moriya-Zeeman model for a perpendicular external magnetic field. We found that certain Kitaev materials provide us with a broad tunability of the MOMNC through a magnetic field. We envision that our findings lead to further investigations of the novel transport properties of the magnon orbital moment.

cond-mat.mes-hall↗

arXiv2023

Intrinsic Magnon Orbital Hall Effect in Honeycomb Antiferromagnets

We theoretically investigate the transport of magnon orbitals in a honeycomb antiferromagnet. We find that the magnon orbital Berry curvature is finite even without spin-orbit coupling and thus the resultant magnon orbital Hall effect is an intrinsic property of the honeycomb antiferromagnet rooted only in the exchange interaction and the lattice structure. Due to the intrinsic nature of the magnon orbital Hall effect, the magnon orbital Nernst conductivity is estimated to be orders of magnitude larger than the predicted values of the magnon spin Nernst conductivity that requires finite spin-orbit coupling. For the experimental detection of the predicted magnon orbital Hall effect, we invoke the magnetoelectric effect that couples the magnon orbital and the electric polarization, which allows us to detect the magnon orbital accumulation through the local voltage measurement. Our results pave a way for a deeper understanding of the topological transport of the magnon orbitals and also its utilization for low-power magnon-based orbitronics, namely magnon orbitronics.

cond-mat.mes-hall↗