Broken time-reversal symmetry in superconducting Pr1−xLaxPt4Ge12

J. Zhang; Z. F. Ding; K. Huang; C. Tan; A. D. Hillier; P. K. Biswas; D. E. MacLaughlin; L. Shu

doi:10.1103/PhysRevB.100.024508

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Broken time-reversal symmetry in superconducting Pr1−xLaxPt4Ge12

J. Zhang, Z. F. Ding, K. Huang, C. Tan, A. D. Hillier, P. K. Biswas, D. E. MacLaughlin, L. Shu

DOI 10.1103/PhysRevB.100.024508 · Physical Review B

T1

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Abstract

The superconducting state of the filled skutterudite alloy series Pr1−xLaxPt4Ge12 has been systematically studied by specific heat and zero-field muon spin relaxation (μSR), while the critical fields have been determined by magnetization measurements. An additional inhomogeneous local magnetic field, indicative of broken time-reversal symmetry, is observed in the superconducting states of the alloys. For x≲0.5, the broken-TRS phase sets in below a temperature Tm, distinctly lower than the superconducting transition temperature Tc. For x≳0.5,Tm≈Tc. The local field strength decreases as x→1, where LaPt4Ge12 is characterized by conventional pairing. The lower critical field Hc1(T) of PrPt4Ge12 shows the onset of a second quadratic temperature region below Tq∼Tm. Upper critical field Hc2(T) measurements suggest multiband superconductivity, and point gap nodes are consistent with the specific heat data. In Pr1−xLaxPt4Ge12, only a single specific-heat discontinuity is observed at Tc, in contrast to the second jump seen in PrOs4Sb12 below Tc. These results suggest that superconductivity in PrPt4Ge12 is characterized by a complex order parameter.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Pr1-xLaxPt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.91	Pressure not reported	onset
Pr0.9La0.1Pt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.85	Pressure not reported	onset
Pr0.7La0.3Pt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.87	Pressure not reported	onset
Pr0.5La0.5Pt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.97	Pressure not reported	onset
Pr0.3La0.7Pt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.02	Pressure not reported	onset
Pr0.2La0.8Pt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.07	Pressure not reported	onset
Pr0.1La0.9Pt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.22	Pressure not reported	onset
LaPt4Ge12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.27	Pressure not reported	onset
PrOs4Sb12 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	1.85	Pressure not reported	unknown