Strong Suppression of Coherence Effect and Appearance of Pseudogap in Layered Nitride Superconductor Li_xZrNCl: ^91Zr- and ^15N- NMR Studies

Abstract

We present NMR measurements of the layered nitride superconductor Li_xZrNCl. The nuclear spin-lattice relaxation rate, 1/T_1, shows that the coherence peak is strongly suppressed in Li_xZrNCl in contrast to conventional BCS superconductors. In the lightly-doped region close to the insulating state, the system shows a gap-like behavior, i.e., pseudogap, that is characterized by a reduction in the magnitude of the Knight shift and 1/T_1T. A higher superconducting (SC) transition temperature, T_c, is achieved by coexisting with the pseudogap state. These unusual behaviors, which deviate from the ordinary BCS framework, are the key ingredients to understanding the SC mechanism of Li_xZrNCl.

5 pages, 5 figures

References in corpus (3)

• Eigenfunction fractality and pseudogap state near superconductor-insulator transition
• High-temperature Superconductivity in Layered Nitrides β-Li${}_x$MNCl (M = Ti, Zr, Hf): Insights from Density-functional Theory for Superconductors
• Localization and Superconductivity in Doped Semiconductors

Cited by in corpus (3)

• Unconventional Superconductivity
• Unconventional Superconductivity in electron-doped layered metal nitride halides $M$N$X$ ($M$ = Ti, Zr, Hf; $X$ = Cl, Br, I)
• Dielectric Response of Electron-doped Ionic Superconductor Li${}_x$ZrNCl