Abrupt enhancement of noncentrosymmetry and appearance of a spin-triplet superconducting state in Li2(Pd1−xPtx)3B beyond x=0.8

S. Harada; J. J. Zhou; Y. G. Yao; Y. Inada; Guo-qing Zheng

doi:10.1103/PhysRevB.86.220502

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Abrupt enhancement of noncentrosymmetry and appearance of a spin-triplet superconducting state in Li2(Pd1−xPtx)3B beyond x=0.8

S. Harada, J. J. Zhou, Y. G. Yao, Y. Inada, Guo-qing Zheng

DOI 10.1103/PhysRevB.86.220502 · Physical Review B

T1

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Abstract

We report synthesis, 195Pt, 11B, and 7Li NMR measurements, and first-principles band calculations for noncentrosymmetric superconductors Li2(Pd1−xPtx)3B (x=0, 0.2, 0.5, 0.8, 0.84, 0.9, and 1). For 0≤x≤0.8, the spin-lattice relaxation rate 1/T1 shows a clear coherence peak just below Tc, decreasing exponentially at low temperature, and the Knight shift 195K decreases below Tc. For x=0.9 and 1.0, in contrast, 1/T1 shows no coherence peak but a T3 variation and 195K remains unchanged across Tc. These results indicate that the superconducting state changes drastically from a spin-singlet dominant to a spin-triplet dominant state at x=0.8. We find that the distortion of B(Pt,Pd)6 increases abruptly above x=0.8, which leads to an abrupt enhancement of the asymmetric spin-orbit coupling as confirmed by band calculation. Such structure distortion that enhances the extent of inversion-symmetry breaking is primarily responsible for the pairing symmetry evolution. The insight obtained here provides a guideline for searching for noncentrosymmetric superconductors with a large spin-triplet component.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Li2Pd3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7	Pressure not reported	unknown
Li2Pt3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.7	Pressure not reported	unknown
Li2(Pd0.8Pt0.2)3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Li2(Pd0.5Pt0.5)3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Li2(Pd0.2Pt0.8)3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Li2(Pd0.16Pt0.84)3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Li2(Pd0.1Pt0.9)3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Li2Pt3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.4	Pressure not reported	unknown
Li2Pt3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.25	Pressure not reported	unknown
Li2Pt3B Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.68	Pressure not reported	unknown