Abstract
We present NMR measurements of the layered nitride superconductor ZrNCl. The nuclear spin-lattice relaxation rate shows that the coherence peak is strongly suppressed in ZrNCl in contrast to conventional BCS superconductors. In the lightly doped region close to the insulating state, the system shows a gaplike behavior, i.e., pseudogap, that is characterized by a reduction in the magnitude of the Knight shift and . A higher superconducting (SC) transition temperature 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 ZrNCl.
- Received 9 January 2014
- Revised 20 June 2014
DOI:https://doi.org/10.1103/PhysRevB.90.020503
©2014 American Physical Society