Superconductivity and the electronic phase diagram of LaPt${}_{2-x}$Ge${}_{2+x}$

Abstract

In many cases, unconventional superconductivity are realized by suppressing another order parameter, such as charge density wave (CDW) or spin density wave (SDW). This suggests that the fluctuations of these order parameters play an important role in producing superconductivity. LaPt${}_2$Ge${}_2$ undergoes a tetragonal-to-monoclinic structural phase transition (SPT) at $T_{\mathrm{s}}$ = 394 K, accompanying a double period modulation in the $a$-axis direction, and superconducts at $T_{\mathrm{c}}$ = 0.41 K. We performed band calculations and found 2D (two dimensional)-like Fermi surfaces with partial nesting. A reduction in the density of states in the monoclinic phase was found in the calculation and confirmed by ${}^{195}$Pt-NMR. We suggest a CDW as a possible cause for the SPT. By changing the stoichiometry between Pt and Ge, we succeeded in suppressing $T_{\mathrm{s}}$ and increasing $T_{\mathrm{c}}$ in LaPt${}_{2-x}$Ge${}_{2+x}$. Comparison of ${}^{139}$La- and ${}^{195}$Pt-NMR data reveals moderate fluctuations associated with SPT. From ${}^{139}$La-NQR measurements at zero field, we found that an isotropic superconducting gap is realized in LaPt${}_{2-x}$Ge${}_{2+x}$ ($x$ = 0.20). We discuss the relationship between superconductivity and the SPT order/fluctuations.

arXiv comment8 pages, 11 figures

References in corpus (9)

• Direct observation of competition between superconductivity and charge density wave order in YBa2Cu3Oy
• Superconductivity at 22 K in Co-doped BaFe2As2 Crystals
• Superconductivity in Cu_xTiSe_2
• Tuning the Charge Density Wave and Superconductivity in CuxTaS2
• Quantum Criticality in Electron-doped BaFe_{2-x}Ni_xAs_2
• Coexistence of Superconductivity and Charge Density Wave in SrPt2As2
• Competition between Superconductivity and Charge Density Wave Ordering in the Lu${}_5$Ir${}_4$(Si${}_{1-x}$Ge${}_x$)${}_{10}$ Alloy System
• Coexistence of multiple charge-density waves and superconductivity in SrPt2As2 revealed by 75As-NMR/NQR and 195Pt-NMR
• Superconductivity in Tetragonal LaPt_{2-x}Ge_{2+x}

Cited by in corpus (3)

• Evolution of charge density wave order and superconductivity under pressure in LaPt${}_2$Si${}_2$
• Charge fluctuations and nodeless superconductivity in quasi-one-dimensional Ta${}_4$Pd${}_3$Te${}_{16}$ revealed by ${}^{125}$Te-NMR and ${}^{181}$Ta-NQR
• Structural phase transition, precursory electronic anomaly and strong-coupling superconductivity in quasi-skutterudite (Sr${}_{1-x}$Ca${}_x$)${}_3$Ir${}_4$Sn${}_{13}$ and Ca${}_3$Rh${}_4$Sn${}_{13}$