Selected Publications

Specific Heat of K0.71Na0.29Fe2As2 at Very Low Temperatures

A. Reifenberger, M. Hempel, P. Vogt, S. Aswartham, M. Abdel-Hafiez, V. Grinenko, S. Wurmehl, S.-L. Drechsler, A. Fleischmann, C. Enss and R. Klingeler

A commercially available calorimeter has been used to investigate the specific heat of a high-quality K0.71Na0.29Fe2As2single crystal.The addenda heat capacity of the calorimeter is determined in the temperature range 0.02K ≤ T ≤ 0.54K. The
data of the K0.71Na0.29Fe2As2 crystal imply the presence of a large T2 contribution to the specific heat which gives evidence of d-wave order parameter symmetry in the superconducting state. To improve the measurements, a novel design for a calorimeter
with a paramagnetic temperature sensor is presented. It promises a temperature resolution of ΔT ≈ 0.1μK and an addenda heat capacity less than 200 pJ/K at T < 100mK.

Journal of Low Temperature Physics 175, 755-763 (2014)

doi: 10.1007/s10909-014-1168-7