The specific heat of two polymorphs of BaPd2As2 was measured. The ThCr2Si2-type polymorph (space group I4/mmm, D4h17, No. 139) is a previously reported superconductor with a transition temperature Tc ≃ 3.5 K, while the CeMg2Si2-type polymorph (P4/mmm, D4h1, No. 123) is a normal metal and does not exhibit superconductivity down to 1.8 K. Our results revealed that the ThCr2Si2-type has an anomalously low Debye temperature, indicative of soft phonons, compared to the CeMg2Si2-type. Moreover, a large specific-heat jump at Tc indicated that the superconductivity of ThCr2Si2-type is a strong-coupling type, which is likely derived from soft phonons.
@article{arxiv.1705.08054,
title = {Strong-Coupling Superconductivity in BaPd2As2 Induced by Soft Phonons in the ThCr2Si2-type Polymorph},
author = {Kazutaka Kudo and Yoshiaki Yamada and Takaaki Takeuchi and Takumi Kimura and Satoshi Ioka and Genta Matsuo and Yutaka Kitahama and Minoru Nohara},
journal= {arXiv preprint arXiv:1705.08054},
year = {2017}
}