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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
Times Cited Count：18 Percentile：73.04(Multidisciplinary Sciences)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 Ba
CuSiO
Cl. 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.
-thiolactam formation in the crystalline stateHosoya, Takaaki*; Uekusa, Hidehiro*; Ohashi, Yuji*; Ohara, Takashi; Tanaka, Ichiro*; Niimura, Nobuo*
Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 62(1), p.153 - 160, 2006/02
Times Cited Count：5 Percentile：48.15(Chemistry, Multidisciplinary)Since N,N-dibenzyl-1-cyclohexenecarbothioamide is photoisomerized to the optically active -thiolactam with the retention of the single-crystal form, the mechanism of chirality induction was identified by X-ray crystal structure analyses during the process of the reaction. In order to clarify the mechanism of hydrogen transfer in the reaction, the H atomsof the benzyl groups were replaced with deuterium atoms. The crystal structure after photoisomerization was analyzed by neutron diffraction. One of four deuterium atoms of the two benzyl groups is transferred to the C atom of the cyclohexene ring. The absolute configuration of the -C
HD- group(chiral methylene) in the photoproduct r-thiolactam revealed that the deuterium atom occupies the equatorial position. This suggests that the deuterium atom is not transferred from the benzyl group of a neighbouring molecule, but from one of the benzyl groups within the molecule.
