Contrasting magnetic structures in SrLaCuSbO and SrLaCuNbO; Spin- quasi-square-lattice - Heisenberg antiferromagnets

Watanabe, Masari*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Ueno, Wataru*; Matsui, Kazuki*; Goto, Takayuki*; Hagihara, Masato

Physical Review B, 105(5), p.054414_1 - 054414_12, 2022/02

https://doi.org/10.1103/PhysRevB.105.054414

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.

Softening of magnetic excitations leading to pressure-induced quantum phase transition in gapped spin system KCuCl

Goto, Kenji*; Osakabe, Toyotaka; Kakurai, Kazuhisa; Uwatoko, Yoshiya*; Osawa, Akira*; Kawakami, Jun*; Tanaka, Hidekazu*

Journal of the Physical Society of Japan, 76(5), p.053704_1 - 053704_4, 2007/05

https://doi.org/10.1143/JPSJ.76.053704

The neutron scattering investigation on magnetic excitations in KCuCl under applied pressure was performed. The softening of the excitation mode at a hydrostatic pressure of 4.7kbar was clearly observed. From the analysis of the dispersion relations, it was found that the intradimer interaction decreases under hydrostatic pressure, while most of the interdimer interactions increase.

Pressure-induced magnetic quantum phase transition in gapped spin system KCuCl

Goto, Kenji; Fujisawa, Masashi*; Tanaka, Hidekazu*; Uwatoko, Yoshiya*; Osawa, Akira*; Osakabe, Toyotaka; Kakurai, Kazuhisa

Journal of the Physical Society of Japan, 75(6), p.064703_1 - 064703_7, 2006/06

https://doi.org/10.1143/JPSJ.75.064703

Magnetization and neutron elastic scattering experiments under hydrostatic pressure were performed on KCuCl, which is a three-dimensionally coupled spin dimer system with a gapped ground state. It was found that the intradimer interaction decreases with increasing hydrostatic pressure, while the sum of the interdimer interactions increases. This leads to the shrinkage of the spin gap. A quantum phase transition from a gapped state to an antiferromagnetic state occurs at Pc8.2 kbar. For PPc, magnetic reflections were observed at reciprocal lattice points equivalent to those for the lowest magnetic excitation at zero temperature. This confirms that the spin gap decreases and closes under applied pressure.

Dynamics of an anisotropic spin dimer system in a strong magnetic field

Kolezhuk, A. K.*; Glazkov, V. N.*; Tanaka, Hidekazu*; Osawa, Akira

Physical Review B, 70(2), p.020403_1 - 020403_4, 2004/07

https://doi.org/10.1103/PhysRevB.70.020403

Recently measured high-field ESR spectra of the spin dimer material TlCuCl are described within the framework of an effective field theory. A good agreement between the theory and experiment is achieved, for all geometries and in a wide field range, under the assumption of a weak anisotropy of the interdimer as well as intradimer exchange interaction.

Field-induced magnetic order and simultaneous lattice deformation in TlCuCl

Vyaselev, O.*; Takigawa, Masashi*; Vasiliev, A.*; Osawa, Akira; Tanaka, Hidekazu*

Physical Review Letters, 92(20), p.207202_1 - 207202_4, 2004/05

https://doi.org/10.1103/PhysRevLett.92.207202

We report the results of Cu and Cl nuclear magnetic resonance experiments and thermal expansion measurements in magnetic fields in the coupled dimer spin system TlCuCl. We found that the field-induced antiferromagnetic transition as confirmed by the splitting of NMR lines is slightly discontinuous. The abrupt change of the electric field gradient at the Cl sites, as well as the sizable change of the lattice constants, across the phase boundary indicate that the magnetic order is accompanied by simultaneous lattice deformation. These results suggest the importance of the spin-lattice correlations in this system.

Neutron diffraction study of the pressure-induced magnetic ordering in the spin gap system TlCuCl

Osawa, Akira; Fujisawa, Masashi*; Osakabe, Toyotaka; Kakurai, Kazuhisa; Tanaka, Hidekazu*

Journal of the Physical Society of Japan, 72(5), p.1026 - 1029, 2003/05

https://doi.org/10.1143/JPSJ.72.1026

no abstracts in English

Magnetic excitations in the spin-gap system TlCuCl

Osawa, Akira*; Kato, Tetsuya*; Tanaka, Hidekazu*; Kakurai, Kazuhisa; Mller, M.*; Mikeska, H.-J.*

Physical Review B, 65(9), p.094426_1 - 094426_7, 2002/03

https://doi.org/10.1103/PhysRevB.65.094426

no abstracts in English

Magnetization and neutron scattering experiments on TlCuCl and KCuCl under applied pressure

Goto, Kenji*; Fujisawa, Masashi*; Osawa, Akira*; Kakurai, Kazuhisa; Osakabe, Toyotaka; Uwatoko, Yoshiya*; Tanaka, Hidekazu*

no journal, , 

no abstracts in English