Browsing by Author "Takeuchi, T"

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    Low-energy excitations and ground-state selection in the quantum breathing pyrochlore antiferromagnet Ba3Yb2Zn5O11
    (American Physical Society (APS), 2016-06-01) Haku, T; Kimura, K; Matsumoto, Y; Soda, M; Sera, M; Yu, DH; Mole, RA; Takeuchi, T; Nakatsuji, S; Kono, Y; Sakakibara, T; Chang, LJ; Masuda, T
    We study low-energy excitations in the quantum breathing pyrochlore antiferromagnet Ba3Yb2Zn5O11 by a combination of inelastic neutron scattering (INS) and thermodynamical property measurements. The INS spectra are quantitatively explained by spin-12 single-tetrahedron model having XXZ anisotropy and Dzyaloshinskii-Moriya interactions. This model has a twofold degeneracy of the lowest-energy state per tetrahedron and well reproduces the magnetization curve at 0.5 K and heat capacity above 1.5 K. At lower temperatures, however, we observe a broad maximum in the heat capacity around 63 mK, demonstrating that a unique quantum ground state is selected due to extra perturbations with an energy scale smaller than the instrumental resolution of INS. ©2024 American Physical Society. All rights reserved.
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    Neutron scattering study in breathing pyrochlore antiferromagnet Ba3Yb2Zn5O11
    (International Conference on Neutron Scattering, 2017-07-12) Masuda, T; Haku, T; Soda, M; Sera, M; Kimura, K; Taylor, J; Itoh, S; Yokoo, T; Matsumoto, Y; Yu, DH; Mole, RA; Takeuchi, T; Nakatsuji, S; Kohno, Y; Sakakibara, T; Chang, LJ
    Comprehensive study on breathing pyrochlore antiferromagnet Ba3Yb2Zn5O11 [1] is presented. To identify the energy scheme of crystalline electric field (CEF), we performed inelastic neutron scattering (INS) measurement in high energy range. The observed dispersionless excitations are explained by a CEF Hamiltonian of Kramers ion Yb3+ of which the local symmetry exhibits C3v point group symmetry. The magnetic susceptibility is consistently reproduced by the energy scheme of the CEF excitations. To identify the spin Hamiltonian we performed INS experiment in low energy range and thermodynamic property measurements at low temperatures. The INS spectra are quantitatively explained by spin-1/2 single-tetrahedron model having XXZ anisotropy and Dzyaloshinskii-Moriya interaction. This model has a two-fold degeneracy of the lowest-energy state per tetrahedron and well reproduces the magnetization curveat 0.5 K and heat capacity above 1.5 K. At lower temperatures, however, we observe a broad maximum in the heat capacity around 63 mK, demonstrating that a unique quantum ground state is selected due to extra perturbations with energy scale smaller than the instrumental resolution of INS. Possible mechanisms for the ground state selection are discussed [2].