SKM 2021 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 12: New Experimental Techniques

TT 12.4: Talk

Wednesday, September 29, 2021, 10:45–11:00, H7

Advanced technique for probing critical elasticity in strongly coupled electron-phonon systems — •Yassine Agarmani, Jan Zimmermann, Steffi Hartmann, Bernd Wolf, and Michael Lang — Institute of Physics, Goethe University Frankfurt, Germany

The recently proposed phenomena of critical elasticity arises from a non-perturbative coupling between lattice and critical electronic degrees of freedom. As demonstrated for the Mott insulator κ-(BEDT-TTF)₂Cu[N(CN)₂]Cl, tuning to the critical endpoint of the first order Mott transition cause a vanishing elastic modulus and a violation of Hooke’s law of elasticity [1, 2]. Similar effects are expected to surround the critical region of the valence transition in EuPd₂Si₂. Measurements of relative length changes under control of temperature and pressure have proven a most sensitive tool for investigating this phenomenon of critical elasticity. In order to develope a deeper understanding of critical elasticity, an expansion of the setup used in Ref. [2] has been designed and realized. It consists of two identical capacitive dilatometer systems, the temperature of which can be controlled individually, and which are connected to a He-gas pressure reservoir. We discuss the new possibilities this system offers for performing high-resolution measurements of relative length changes over wide ranges of temperature and pressure.
[1] Zacharias et al., Eur. Phys. J. Spec. Top. 224, 1021-1040 (2015)
[2] Gati et al., Sci. Adv. 2, e1601646 (2016)