arXiv subjects

Ryota Yambe

Publications and source records attributed to Ryota Yambe.

21 records · Page 2Linked to original sources

arXiv2021

Field-Direction Sensitive Skyrmion Crystals in Cubic Chiral Systems: Implication to $4f$-Electron Compound EuPtSi

We theoretically study the stability of magnetic skyrmion crystals (SkXs) in chiral cubic antiferromagnets with the EuPtSi hosting unconventional nanometric SkXs in mind. By performing numerical simulations for a minimal effective spin model with the long-range Dzyaloshinskii-Moriya interaction and the multiple-spin interaction arising from itinerant nature of electrons, we clarify two key ingredients for the emergence of the SkXs in EuPtSi: One is the low-symmetric ordering vectors that lead to the field-direction sensitive SkXs in an external magnetic field, while the other is the synergy between spin-charge and spin-orbit couplings in itinerant magnets that results in the nanometric SkXs. The present study will not only provide the microscopic mechanism of the SkXs in EuPtSi but also guide for a search of further materials hosting short-period SkXs.

cond-mat.str-el↗

arXiv2020

Degeneracy Lifting of Néel, Bloch, and Anti-Skyrmion Crystals in Centrosymmetric Tetragonal Systems

A skyrmion crystal has internal degrees of freedom in terms of vorticity and helicity, which gives rise to fascinating types of skyrmion phases (Néel, Bloch, and anti-skyrmion). We show how the degeneracy lifting in tetragonal skyrmion crystals occurs in centrosymmetric itinerant magnets by focusing on microscopic interactions through the Fermi surface instability. We demonstrate that four types of skyrmion crystals can be realized according to the signs of the anisotropic Ruderman-Kittel-Kasuya-Yosida interaction, which are sensitive to band structures, electron fillings, atomic orbitals, and sublattice positions. Our findings might provide a possibility of controlling the types of the skyrmion crystals by electron doping and external pressure rather than relying on the noncentrosymmetric lattice structures.

cond-mat.str-el↗

arXiv2019

Double-$Q$ Chiral Stripe in the $d$-$p$ Model with Strong Spin-Charge Coupling

We investigate the stability of multiple-$Q$ spiral states in $d$-$p$ electron systems with the strong spin-charge coupling. By using variational calculations on a square lattice, we find that the double-$Q$ state with the scalar chirality density wave, which has been studied in the weak spin-charge coupling regime, becomes the ground state even in the strong spin-charge coupling regime by considering the effect of the $d$-$p$ hybridization. We also show that the regions where the double-$Q$ state is stabilized are widely extended for introducing the antiferromagnetic superexchange interaction between nearest-neighbor localized spins.

cond-mat.str-el↗