Superconducting characteristics in electron-doped layered hafnium nitride: 15N isotope effect studies

Hideki Tou; Yutaka Maniwa; Shoji Yamanaka

doi:10.1103/PhysRevB.67.100509

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Superconducting characteristics in electron-doped layered hafnium nitride: 15N isotope effect studies

Hideki Tou, Yutaka Maniwa, Shoji Yamanaka

DOI 10.1103/PhysRevB.67.100509 · Physical Review B

T1

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Abstract

We report 15N nuclear magnetic resonance (NMR) and the nitrogen-isotope effect studies on c-axis oriented sample of Li-doped HfNCl with superconducting transition temperature Tc∼25.5K. 15N NMR Knight shift decreases toward zero below Tc, giving evidence that the pairing symmetry is an even-parity spin singlet, and that the nitrogen site plays an important role in the occurrence of superconductivity. A nitrogen isotope shift is found to be quite small, ΔTc∼0.1K (αN=0.07±0.02), which cannot reproduce such a high Tc within the traditional BCS framework.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Li0.48(THF)0.3HfNCl Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	25.5	Pressure not reported	onset
Li-Hf14NCl Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	25.5	Pressure not reported	onset
Li-Hf15NCl Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	25.4	Pressure not reported	onset