arXiv subjects

Masashi Hosoi

Publications and source records attributed to Masashi Hosoi.

6 recordsLinked to original sources

arXiv2023

Uncovering footprints of dipolar-octupolar quantum spin ice from neutron scattering signatures

Recent experiments on Ce$_2$Zr$_2$O$_7$ suggest that this material may host a novel form of quantum spin ice, a three-dimensional quantum spin liquid with an emergent photon. The Ce$^{3+}$ local moments on the pyrochlore lattice are described by pseudospin 1/2 degrees of freedom, whose components transform as dipolar and octupolar moments under symmetry operations. In principle, there exist four possible quantum spin ice regimes, depending on whether the Ising component is in the dipolar/octupolar channel, and two possible flux configurations of the emergent gauge field. In this work, using exact diagonalization and molecular dynamics, we investigate the equal-time and dynamical spin structure factors in all four quantum spin ice regimes using quantum and classical computations. Contrasting the distinct signatures of quantum and classical results for the four possible quantum spin ice regimes and elucidating the role of quantum fluctuations, we show that the quantum structure factor computed for the $π$-flux octupolar quantum spin ice regime is most compatible with the neutron scattering results on Ce$_2$Zr$_2$O$_7$.

cond-mat.str-el↗

arXiv2021

Thin Films of Topological Nodal Line Semimetals as a Candidate for Efficient Thermoelectric Converters

Thermoelectric materials intrigue much interest due to their wide range of application such as power generators and refrigerators. The efficiency of thermoelectric materials is quantified by the figure of merit, and a figure greater than unity is desired. To achieve this, a large Seebeck coefficient and low phonon thermal conductivity are required. We show that this can be achieved with a thin film of topological nodal line semimetals. We also discusses the correlation effect and spin current induced by a temperature gradient. The obtained results provide insight for the improvement of thermoelectric materials.

cond-mat.mes-hall↗

arXiv2020

Distinguishing dipolar and octupolar quantum spin ices using contrasting magnetostriction signatures

Recently there have been a number of experiments on Ce$_2$Zr$_2$O$_7$ and Ce$_2$Sn$_2$O$_7$, suggesting that these materials host a three-dimensional quantum spin liquid with emergent photons and fractionalized spinon excitations. However, the interpretation of the data to determine the precise nature of the quantum spin liquids is still under debate. The Kramers doublet in Ce$^{3+}$ local moment offers unusual pseudo-spin degrees of freedom as the $x$ and $z$ components transform as a dipole and $y$ component as an octupole. This leads to a variety of possible quantum spin liquid (or quantum spin ice) phases on the pyrochlore lattice of Ce$^{3+}$ moments. In this work, we theoretically propose that magnetostriction would be able to distinguish the dipolar (D-QSI) and octupolar (O-QSI) quantum spin ice, where the dipolar or octupolar components possess the respective spin ice correlations. We show that the magnetostriction in various configurations can be used as a selection rule to differentiate not only D-QSI and O-QSI, but also a number of competing broken symmetry states.

cond-mat.str-el↗

arXiv2020

Theory of magnetostriction for multipolar quantum spin ice in pyrochlore materials

Multipolar magnetism is an emerging field of quantum materials research. The building blocks of multipolar phenomena are magnetic ions with a non-Kramers doublet, where the orbital and spin degrees of freedom are inextricably intertwined, leading to unusual spin-orbital entangled states. The detection of such subtle forms of matter has, however, been difficult due to a limited number of appropriate experimental tools. In this work, motivated by a recent magnetostriction experiment on Pr$_2$Zr$_2$O$_7$, we theoretically investigate how multipolar quantum spin ice, an elusive three dimensional quantum spin liquid, and other multipolar ordered phases in the pyrochlore materials can be detected using magnetostriction. We provide theoretical results based on classical and/or quantum studies of non-Kramers and Kramers magnetic ions, and contrast the behaviors of distinct phases in both systems. Our work paves an important avenue for future identification of exotic ground states in multipolar systems.

cond-mat.str-el↗

arXiv2020

Dzyaloshinskii-Moriya Interaction between Multipolar Moments in $5d^1$ Systems

We propose a new type of Dzyaloshinskii-Moriya (DM) interactions which act on high-rank multipolar moments such as quadrupolar and octupolar moments. Here we consider 5d1 systems with broken spatial inversion symmetry, where the interplay of electron correlation, the spin-orbit coupling, and inversion symmetry breaking plays a crucial role. Using a numerical diagonalization on a two-site multiorbital Hubbard model, we reveal that anti-symmetric products of multipole operators have finite expectation values, indicating the existence of DM interactions for multipoles. We also find that the spin-orbit coupling dependences of DM interactions for multipoles are significantly different depending on the lattice structure. Finally, we discuss the numerical results for small and large spin-orbit coupling region by using perturbative analysis.

cond-mat.str-el↗

arXiv2018

New magnetic phases on chiral magenet CsCuCl$_3$ under high pressures

We study a magnetic phase diagram of CsCuCl3 by a spin wave theory. We clarify an existence of new magnetic phases, i.e. up-up-down (uud) phase and Y coplanar phase under a high pressure. We also discuss a magnetic field(H)-temperature(T) phase diagram under ambient and high pressures.

cond-mat.mtrl-sci↗