Enhancement of density of states and suppression of superconductivity in site-disordered topological metal LaPtSi

Abstract

Single crystals of non-centrosymmetric $s$-wave superconductor LaPt${}_{0.88}$Si${}_{1.12}$ have been grown by the Czochralski (Cz) technique, whose crystal structure is described by the space group $I4{}_{1}md$ at ambient conditions. The inter-site mixing between platinum and silicon is confirmed by both single-crystal x-ray diffraction (SXRD) and electron probe micro-analyzer (EPMA). The disordered material exhibits a lower superconducting (SC) transition temperature $T_c$ at 2.02 K as opposed to the highest value of 3.9 K reported in polycrystalline LaPtSi without inter-site mixing. From specific heat, the Sommerfeld coefficient ($\gamma$) is estimated to be 7.85 mJ/mol K${}^2$, which is much larger than the values reported for the samples exhibiting higher $T_c$. This is unprecedented as $T_c$ seems to decrease with increase in the electron density of states (DOS) at the Fermi energy and thus $\gamma$. The present work reports on the anomalous behaviour of SC and normal state properties of LaPt${}_x$Si${}_{2-x}$, presumably caused due to the existence of non-trivial topological bands.