Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 13: Frustrated Magnets - Spin Liquids (joint session TT/MA)

TT 13.14: Vortrag

Montag, 1. April 2019, 18:30–18:45, Theater

Thermal expansion studies on the spin-liquid candidate system κ-(BEDT-TTF)₂Ag₂(CN)₃ — •S. Hartmann¹, E. Gati², Y. Yoshida³, G. Saito⁴, and M. Lang¹ — ¹Physikalisches Institut, SFB/TR 49, Goethe-Uni Frankfurt, Germany — ²Ames Laboratory, Iowa State University, USA — ³Division of Chemistry, Kyoto University, Japan — ⁴Toyota Physical and Chemical Research Institute, Nagakute, Japan

The search for the realization of a quantum spin-liquid (QSL) is a major concern for condensed matter physicists since its proposal in 1973. The entangled QSL state lacks magnetic ordering down to lowest temperatures where spins continue to fluctuate even at T = 0 K [1]. One way to experimentally realize a QSL is magnetic frustration of geometric origin, inherent to the quasi-2D triangular lattice of the organic charge-transfer salts κ-(BEDT-TTF)₂X, known as weak Mott insulators. We present results of ultra-high-resolution thermal expansion measurements on the newly-synthesized QSL-candidate system X = Ag₂(CN)₃. Our main finding includes pronounced broad extrema in the thermal expansion coefficient at T ∼ 18 K along all three crystallographic directions which we assign to the effect of strong electronic correlations. The observed anomalies are qualitatively consistent with theoretical results based on the Hubbard model on a triangular lattice [2]. The directional anisotropy of the anomalies implies a ratio of the hopping integrals t’/t < 1.
Balents, Nature 2010
Kokalj, McKenzie, PRB 2015