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TT: Fachverband Tiefe Temperaturen

TT 19: Poster Session: Correlated Electrons 1

TT 19.15: Poster

Montag, 20. März 2017, 15:00–19:00, P2-EG

Thermal expansion measurements on Cs₂CuCl_4−xBr_x at sub-Kelvin temperatures — •Satya Krishna Thallapaka, Christian Thurn, Ulrich Tutsch, Bernd Wolf, and Michael Lang — Physikalisches Institut, SFB/TR49, Goethe Uni Frankfurt, DE

In recent years, Cs₂CuCl₄ and Cs₂CuBr₄ have been extensively investigated both experimentally and theoretically, as they represent model systems for quasi-2D triangular-lattice quantum antiferromagnets. They attracted much attention due to their unconventional magnetic properties resulting from the interplay of strong quantum fluctuations in reduced dimensions, geometrical frustration and effects of spin-lattice interactions close to the field-induced quantum critical point (QCP). Recently, a study of the mixed system Cs₂CuCl_4−xBr_x has identified two novel compounds [1] with well-ordered halide sublattices due to a site-selective substitution mechansim, namely Cs₂CuCl₃Br₁ and Cs₂CuCl₂Br₂. It was predicted that the latter compound is showing an even higher degree of frustration than the border compounds. Thus, the series Cs₂CuCl_4−xBr_x is ideal to study the effects of frustration and dimensionality around the QCP. To this end, we will present measurements of the thermal expansion coefficient on Cs₂CuCl₄ down to T = 40 mK around the field-induced QCP. The thermal expansion coefficient has been proven to be particularly suited to probe the anomalous thermodynamics of QCPs [2]. In addition, we will compare these results to measurements of the thermal expansion on the mixed system Cs₂CuCl₂Br₂ and to specific heat measurements.

[1] Cong et al., PRB 83, 064425 (11)

[2] Zhu et al., PRL 91, 066404 (03)