Superconductivity-Electron Count Relationship in Heusler Phases-the Case of LiPd2Si

Karolina Górnicka; Xin Gui; Juan R Chamorro; Tyrel M McQueen; Robert J Cava; Tomasz Klimczuk; Michał J Winiarski

doi:10.1021/acs.chemmater.3c02398

Superconductivity-Electron Count Relationship in Heusler Phases-the Case of LiPd₂Si

Chem Mater. 2024 Feb 15;36(4):1870-1879. doi: 10.1021/acs.chemmater.3c02398. eCollection 2024 Feb 27.

Authors

Karolina Górnicka¹, Xin Gui², Juan R Chamorro³, Tyrel M McQueen⁴, Robert J Cava², Tomasz Klimczuk¹, Michał J Winiarski¹

Affiliations

¹ Faculty of Applied Physics and Mathematics and Advanced Materials Centre, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdańsk, Poland.
² Department of Chemistry, Princeton University, Princeton, New Jersey 08540, United States.
³ Materials Department and Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
⁴ Department of Chemistry, William H. Miller III Department of Physics and Astronomy, Department of Materials Science and Engineering, and Institute for Quantum Matter, Johns Hopkins University, Baltimore, Maryland 21218, United States.

Abstract

We report superconductivity in the full Heusler compound LiPd₂Si (space group Fm3̅m, No. 225) at a critical temperature of T_c = 1.3 K and a normalized heat capacity jump at T_c, ΔC/γT_c = 1.1. The low-temperature isothermal magnetization curves imply type-I superconductivity, as previously observed in LiPd₂Ge. We show, based on density functional theory calculations and using the molecular orbital theory approach, that while LiPd₂Si and LiPd₂Ge share the Pd cubic cage motif that is found in most of the reported Heusler superconductors, they show distinctive features in the electronic structure. This is due to the fact that Li occupies the site which, in other compounds, is filled with an early transition metal or a rare-earth metal. Thus, while a simple valence electron count-property relationship is useful in predicting and tuning Heusler materials, inclusion of the symmetry of interacting frontier orbitals is also necessary for the best understanding.