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TT: Fachverband Tiefe Temperaturen

TT 9: Poster Session: Correlated Electrons

TT 9.24: Poster

Dienstag, 28. September 2021, 13:30–16:00, P

Glass-like transitions in the frustrated charge system θ-(BEDT-TTF)2CsM(SCN)4 (M = Cs and Co) revealed by thermal expansion measurements — •Yohei Saito1, Tatjana Thomas1, Steffi Hartmann1, Tim Thyzel1, Yassine Agarmani1, Hungwei Sun1, Jens Müller1, Kenichiro Hashimoto2, Takahiko Sasaki2, Hiroshi Yamamoto3, and Michael Lang11Institute of Physics, Goethe University Frankfurt, Frankfurt (M), Germany — 2Institute for Materials Research, Tohoku University, Sendai, Japan — 3Institute for Molecular Science, Okazaki, Japan

Geometrical frustration causes degenerate states, giving rise to intriguing quantum phenomena such as a spin liquid. In addition to a frustrated spin system, a frustrated charge system is proposed in organic conductors called θ-type BEDT-TTF salts. It is expected that charge ordering is suppressed and is possibly replaced by a charge glass state. In organic charge-ordered salts, the charge order transition accompanies a structural transition. Therefore, investigating their elastic properties is of fundamental interest. We performed thermal expansion measurements on θ-(BEDT-TTF)2CsM(SCN)4 (M = Cs and Co) that does not show charge ordering. The thermal expansion coefficient exhibited a glassy transition at 90-100 K. This behavior is reminiscent of the freezing of the terminal ethylene end-groups on the BEDT-TTF molecules. We also found another glassy transition at 120-130 K for both salts where the development of a superlattice structure was reported. These results point to the importance of the lattice degrees of freedom in the frustrated charge system.

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DPG-Physik > DPG-Verhandlungen > 2021 > SKM