Pressure-induced enhancement of superconductivity in a non-centrosymmetric compound LaPtGe
arxiv(2024)
摘要
We report a pressure-induced enhancement of the superconducting transition
temperature (Tc) in a non-centrosymmetric (NCS) compound, LaPtGe. With
pressure, till 3 GPa, we observed a modest enhancement of the Tc with a rate of
0.071 K/GPa. However, above this pressure, the rate showed a 2.5 times
increase, 0.183 K/GPa. We observed a Tc of 3.94 K at 6 GPa, the highest
pressure value used in our transport study. Synchrotron high-pressure x-ray
powder diffraction (HP-XRPD) measurements do not reveal any structural phase
transition in this system in this pressure range. However, it showed an
apparent change of slope in the pressure dependence of lattice parameters above
and below 3 GPa. Pressure dependence of the unit-cell volume also followed a
distinct trend below and above 3 GPa, with the Birch-Murnaghan equation of
state fit providing a bulk modulus (B0) value of 144 and 162 GPa,
respectively, for two pressure regions. Further, the magnetotransport
measurement under pressure up to 2.45 GPa reveals the enhancement of the upper
critical field (Hc2(0)) from 0.7 T (0 GPa) to 0.92 T (2.45 GPa). In addition,
the upward curvature in Hc2(T) becomes stronger with increasing pressure,
suggesting a change of the underlying Fermi surface topology with pressure. The
signature for the inducible Hc2(T) with pressure, the distinct enhancement of
Tc around 3 GPa, and the noticeable change in lattice parameters around 3 GPa
suggests the possibility of multi-gap superconductivity in LaPtGe similar to
identical structure NCS compound, LaPtSi. The enhancement of Tc by pressure can
be correlated with the possible underlying lattice modulation by compression
and the change in the density of states at the Fermi level. Also, the bare
change in pressure-dependent activation energy U0 up to 2.45 GPa calculated
using the Arrhenius relation clearly shows that the shift in Tc does not arise
from grain boundaries.
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