Evolution of charge density wave order and superconductivity under pressure in LaPt2Si2

Abstract

We report measurements of the electrical resistivity and ac magnetic susceptibility of single crystalline LaPt2Si2 under pressure, in order to investigate the interplay of superconductivity and CDW order. LaPt2Si2 exhibits a first order phase transition from a tetragonal to orthorhombic structure, accompanied by the onset of CDW order below TCDW = 76 K, while superconductivity occurs at a lower temperature of Tc = 1.87 K. We find that the application of pressure initially suppresses the CDW transition, but enhances Tc. At pressures above 2.4 GPa, CDW order vanishes, while both Tc and the resistivity A-coefficient reach a maximum value around this pressure. Our results suggest that the occurrence of a superconducting dome can be accounted for within the framework of BCS theory, where there is a maximum in the density of states upon the closure of the CDW gap.

Interplay between charge density wave and superconductivity in multiband systems with interband Coulomb interaction

“…Figures 6(a) and 6(b) exhibit a qualitative agreement with experimental results for compounds that present a discontinuous vanishing of the CDW transition with pressure [54], although with a persistent SC phase at low temperatures. The reentrant behavior of T CDW for large values of U dc and away from half-filling is a signature of a first-order phase transition [78].…”

“…There is a longstanding question concerning the competition, coexistence, or even cooperation between CDW and SC, as well as about the nature of the CDW phase transition. For the phase transition, several works reported a first-order structural phase transition where pressure initially suppresses the CDW, but enhances the superconducting transition temperature T SC [54], whereas others find a second-order phase transition that extrapolates to a structural quantum critical point (SQCP), around which a dome-shaped variation of T SC is found [37,38,55]. For instance, for the compound LaPt 2 Si 2 [54] with transition temperature T SC = 1.87 K and a superlattice structural transition at T = 76 K, it is suggested that the occurrence of a SC dome-like can be accounted for, within the BCS theory, assuming there is a maximum in the density of states N (E F ) upon the closure of the CDW gap.…”

“…For the phase transition, several works reported a first-order structural phase transition where pressure initially suppresses the CDW, but enhances the superconducting transition temperature T SC [54], whereas others find a second-order phase transition that extrapolates to a structural quantum critical point (SQCP), around which a dome-shaped variation of T SC is found [37,38,55]. For instance, for the compound LaPt 2 Si 2 [54] with transition temperature T SC = 1.87 K and a superlattice structural transition at T = 76 K, it is suggested that the occurrence of a SC dome-like can be accounted for, within the BCS theory, assuming there is a maximum in the density of states N (E F ) upon the closure of the CDW gap. Then, the evolution of T SC under pressure is likely driven by the variation of N (E F ), with a sudden disappearance of CDW order, which indicates that there is a first-order structural transition suggesting the lack of a QCP in this material [54].…”

“…For instance, for the compound LaPt 2 Si 2 [54] with transition temperature T SC = 1.87 K and a superlattice structural transition at T = 76 K, it is suggested that the occurrence of a SC dome-like can be accounted for, within the BCS theory, assuming there is a maximum in the density of states N (E F ) upon the closure of the CDW gap. Then, the evolution of T SC under pressure is likely driven by the variation of N (E F ), with a sudden disappearance of CDW order, which indicates that there is a first-order structural transition suggesting the lack of a QCP in this material [54]. On the other hand, the cubic superconducting intermetallic systems Lu(Pt 1−x Pd x ) 2 In and (Sr 1−x Ca x ) 3 Ir 4 Sn 13 present second-order CDW phase transitions under chemical doping and pressure, respectively [56].…”

“…We are particularly interested in intermetallic compounds and their alloys [13], like the layered SCs SrPt 2 As 2 and LaPt 2 Si 2 [54,57], the cubic superconducting systems Lu(Pt 1−x Pd x ) 2 In and (Sr 1−x Ca x ) 3 Ir 4 Sn 13 [56], the cubic Heusler alloys Lu(Pt 1−x Pd x ) 2 In [3], and the large family of superconducting stannides with composition A 3 T 4 Sn 13 , where A = La; Sr; Ca and T = Rh; Ir [58]. These systems have in common a rather narrow d-band with moderate electronic correlations (as compared with the f -bands in heavy fermions, where a large U approach is necessary [59]) coexisting with large sp-bands [60].…”