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TT: Fachverband Tiefe Temperaturen

TT 34: Fe-based Superconductors

TT 34.5: Talk

Wednesday, March 29, 2023, 12:30–12:45, HSZ 103

The low-temperature specific heat and thermal expansion of YFe₂Ge₂ — •Pavlo Khanenko^1,2, Jiasheng Chen², Jacintha Banda¹, Thomas Luehmann¹, F. Malte Grosche², and Manuel Brando¹ — ¹Max Planck Institute for Chemical Physics of Solids, Germany — ²Cavendish Laboratory, University of Cambridge, Cambridge, UK

We present specific heat and thermal expansion coefficient measurements of the layered iron-based superconductor YFe₂Ge₂ down to 40 mK and in magnetic field. A new generation of crystals [1] with residual resistivity ratios larger than 500 and T_c = 1.2 K have been investigated. These crystals display a sharp superconducting anomaly in both specific heat and thermal expansion. From the jump magnitudes and using the Ehrenfest relation we derive a small positive pressure dependence of T_c, dT_c/dp = 24.4  mK/GPa. Despite the high purity of the crystals, the residual Sommerfeld coefficient is relatively large γ₀ ≈ 40 mJ/K²mol, i.e., less than about half of the value in the normal state (100 mJ/K²mol). The field dependences of γ₀(B) and its respective coefficient in thermal expansion α₀(B) are analyzed within the frame of two gap scenario.

[1] J. Chen et al., Phys. Rev. Lett. 125, 237002 (2020)