Dresden 2020 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 48: Poster Session: Many Body Systems, Quantum Critical Phenomena

TT 48.2: Poster

Mittwoch, 18. März 2020, 15:00–19:00, P2/4OG

A.C. susceptibility investigations near quantum critical points on strongly correlated spin systems — •Paul Eibisch, Lars Postulka, Bernd Wolf, Ulrich Tutsch, Yeekin Tsui, Franz Ritter, Cornelius Krellner, and Michael Lang — Physikalisches Institut Goethe-Universität

Quantum phase transitions (QPT), i.e., phase transitions at T = 0 driven by the variation of a control parameter such as the magnetic field B, continue to be of high interest in condensed matter research. Above the quantum critical point (QCP) the system shows quantum critical behaviour which manifests itself in scaling behaviour of thermodynamic quantities and divergences in certain ratios of these quantities, the so-called Grüneisen parameters. In addition to signatures in these equilibrium properties, quantum criticality is expected to affect also the dynamic properties via a critical slowing down, i.e., the divergence of the correlation time at the QPT. Here we present a study of the a.c. susceptibility, including both the real- and imaginary-contributions, on the low-dimensional quantum spin systems CuSO4 and Cs2CuCl4 both of which show B-induced quantum critical points in the field range B≤ 10 T. At the critical fields for T<1 K we find clear signals in the imaginary part, χ″ of the a.c. susceptibility, yielding a pronounced maximum at finite temperature. The position of these anomalies in the B-T-phase diagram suggests a quantum critical nature, i.e., changes in the spin dynamics on approaching the QCP.

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