Structures of magnetic excitations in the spin- kagome-lattice antiferromagnets CsCuSnF and RbCuSnF

Saito, Mutsuki*; Takagishi, Ryunosuke*; Kurita, Nubuyuki*; Watanabe, Masari*; Tanaka, Hidekazu*; Nomura, Ryuji*; Fukumoto, Yoshiyuki*; Ikeuchi, Kazuhiko*; Kajimoto, Ryoichi

Physical Review B, 105(6), p.064424_1 - 064424_15, 2022/02

https://doi.org/10.1103/PhysRevB.105.064424

Magnons and spinons in BaCoTeO; A Composite system of isolated spin- triangular Heisenberg-like and frustrated honeycomb Ising-like antiferromagnets

Kojima, Yuki*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Nakajima, Kenji

Physical Review B, 105(2), p.L020408_1 - L020408_6, 2022/01

https://doi.org/10.1103/PhysRevB.105.L020408

We report the neutron scattering results on magnetic orderings and excitations in BaCoTeO composed of two almost isolated subsystems A and B, which are described as an triangular Heisenberg-like antiferromagnet and a frustrated honeycomb Ising-like antiferromagnet, respectively. It was found that the excitation spectra of both subsystems are well separated and independent of each other. The excitation spectrum of subsystem A is composed of two single-magnon branches with roton-like minima at the M point and a clearly structured intense continuum, as similarly observed in BaCoSbO, which is strongly indicative of spinon excitations. Dispersion curves for subsystem B can be described by linear spin wave theory within the third-neighbor exchange interaction.

Triplon band splitting and topologically protected edge states in the dimerized antiferromagnet

Nawa, Kazuhiro*; Tanaka, Kimihito*; Kurita, Nubuyuki*; Sato, Taku*; Sugiyama, Haruki*; Uekusa, Hidehiro*; Kawamura, Seiko; Nakajima, Kenji; Tanaka, Hidekazu*

Nature Communications (Internet), 10, p.2096_1 - 2096_8, 2019/05

https://doi.org/10.1038/s41467-019-10091-6

Search for topological materials has been actively promoted in the field of condensed matter physics for their potential application in energy-efficient information transmission and processing. Recent studies have revealed that topologically invariant states, such as edge states in topological insulators, can emerge not only in a fermionic electron system but also in a bosonic system, enabling nondissipative propagation of quasiparticles. Here we report the topologically nontrivial triplon bands measured by inelastic neutron scattering on the spin-1/2 two-dimensional dimerized antiferromagnet BaCuSiOCl. The excitation spectrum exhibits two triplon bands that are clearly separated by a band gap due to a small alternation in interdimer exchange interaction, consistent with a refined crystal structure. By analytically modeling the triplon dispersion, we show that BaCuSiOCl is the first bosonic realization of the coupled Su-Schrieffer-Heeger model, where the presence of topologically protected edge states is prompted by a bipartite nature of the lattice.

Delocalization of the electron in CeLaRuSi; The de Haas-van Alphen effect measurement

Matsumoto, Yuji; Kimura, Noriaki*; Komatsubara, Takemi*; Aoki, Haruyoshi*; Kurita, Nubuyuki*; Terashima, Taichi*; Uji, Shinya*

Journal of Physics; Conference Series, 391, p.012042_1 - 012042_4, 2012/12

https://doi.org/10.1088/1742-6596/391/1/012042

CeRuSi is a paramagnetic heavy fermion compound with the electronic specific heat coefficient of 350 mJ/mol K. When a magnetic field is applied along the [001] direction of its tetragonal ThCrSi structure, it exhibits metamagnetic transition at 7.7 T. On the other hand, when a magnetic field is applied in the (001) plane, metamagnetic transition does not occur. This magnetic anisotropy is maintained to lower Ce concentration samples. By replacing Ce with La, CeRuSi changes to antiferromagnet at 0.91 and finally to normal paramagnet of LaRuSi. In very low Ce concentration samples, the impurity Kondo effect is observed. The Kondo temperature of the = 0.02 sample is about 1 K. We have successfully observed all the dHvA oscillations in the dilute Ce concentration samples with fields in the (001) plane. Moreover, we have observed the variation of the dHvA oscillations with temperature crossing the Kondo temperature.

Change of Fermi surface properties in dilute Ce concentration of CeLaRuSi system, 3

Matsumoto, Yuji; Kimura, Noriaki*; Komatsubara, Takemi*; Aoki, Haruyoshi*; Kurita, Nubuyuki*; Terashima, Taichi*; Uji, Shinya*

no journal, , 

We have performed the de Haas - van Alphen (dHvA) effect measurements in CeLaRuSi with magnetic fields in the (001) plane. All the oscillations corresponding to those in LaRuSi can be observed in low Ce concentration samples and the evolution of the Fermi surface properties with x is found to depend strongly on the Fermi surface sheet. We will argue that the evolution can be attributed to anisotropic hybridization of the f electron with conduction electrons and resultant delocalization of the f electron.

Detail measurement on non-Kitaev term spin dynamics in -RuCl

Nakajima, Kenji; Kojima, Yuki*; Kurita, Nubuyuki*; Tanaka, Hidekazu*

no journal, , 

Kitaev model is an exactly solvable model which has a quantum spin liquid state as the ground state. In Kitaev model, S=1/2 spins arranged on a honeycomb lattice are connected via three non-equivalent bonds with Ising-type interactions. -RuCl has been considered to be an excellent candidate of a Kitaev material. On the other hand, as a real material, the system has deviations from the ideal Kitaev model. The interaction between spins has non-Kitaev (Heisenberg) term as well as Kitaev one, which makes the exact ground state of -RuCl rather difficult to understand. We have studied spin dynamics in -RuCl by means of neutron scattering technique especially in low temperature and relatively lower energy range to obtained the detail picture of the ground state spin dynamics in this system, in which the non-Kitaev term highly contributes. Detail of our results and analysis will be shown in our presentation.

Magnons and spinons in BaCoTeO; A Composite system of spin-1/2 triangular Heisenberg and honeycomb Ising antiferromagnets

Kojima, Yuki*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Nakajima, Kenji

no journal, , 

We report the neutron scattering results for magnetic orderings and excitations in BaCoTeO composed of two subsystems, A and B, which are described as an S = 1/2 triangular Heisenberg-like antiferromagnet and a frustrated honeycomb Ising-like antiferromagnet, respectively.