Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 64: Frustrated Magnets - α-RuCl₃ and Cu-based Materials

TT 64.10: Vortrag

Mittwoch, 14. März 2018, 17:30–17:45, HFT-FT 101

Thermodynamic investigations of the anisotropic triangular Heisenberg antiferromagnet Cs₂CuCl_4−xBr_x — •Ulrich Tutsch¹, Oleksandr Tsyplyatyev², Lars Postulka¹, Markus Kuhnt¹, Bernd Wolf¹, Natalija van Well¹, Franz Ritter¹, Cornelius Krellner¹, Burkhard Schmidt³, Peter Kopietz², and Michael Lang¹ — ¹Physikalisches Institut and — ²Institut für Theoretische Physik, Goethe-Universität Frankfurt, SFB/TR 49, 60438 Frankfurt (M), Germany — ³Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany

The system Cs₂CuCl_4−xBr_x is known to be a good realization of the S = 1/2 2D anisotropic triangular Heisenberg antiferromagnet. Its border compounds (x = 0, 4) have been intensively studied by neutron scattering experiments, ESR and thermodynamic methods, so that the ratio J′/J of the coupling constants of 0.34 (x = 0) and 0.41 (x = 4) is known with a high degree of accuracy. We will present specific heat results for the two intermediate compounds with x = 1, 2 which can be synthesized with a fully ordered halide sublattice when grown at relatively low temperatures from an aqueous solution. A C ∝ T behaviour is observed at low temperatures for both compounds although Cs₂CuCl₂Br₂ already shows a rather high value J′/J≈0.7. Our experimental results are in good agreement with our theoretical calculations, which demonstrate that a C ∝ T behaviour at low temperatures can be a result of strong quantum fluctuations in S = 1/2 2D anisotropic triangular Heisenberg antiferromagnets, contrary to the general believe that it reflects quasi-1D behaviour.