Using controlled disorder to probe the interplay between charge order and superconductivity in NbSe2

Kyuil Cho,A I Goldman,V Mishra,R J Mcqueeney,P J Hirschfeld,R Prozorov,A Kreyssig,M Kończykowski,S Teknowijoyo,P B Gartin,J Guss,M A Tanatar,J M Wilde

doi:10.1038/s41467-018-05153-0

Abstract

The interplay between superconductivity and charge-density wave (CDW) in 2H-NbSe2 is not fully understood despite decades of study. Artificially introduced disorder can tip the delicate balance between two competing long-range orders, and reveal the underlying interactions that give rise to them. Here we introduce disorder by electron irradiation and measure in-plane resistivity, Hall resistivity, X-ray scattering, and London penetration depth. With increasing disorder, the superconducting transition temperature, Tc, varies non-monotonically, whereas the CDW transition temperature, TCDW, monotonically decreases and becomes unresolvable above a critical irradiation dose where Tc drops sharply. Our results imply that the CDW order initially competes with superconductivity, but eventually assists it. We argue that at the transition where the long-range CDW order disappears, the cooperation with superconductivity is dramatically suppressed. X-ray scattering and Hall resistivity measurements reveal that the short-range CDW survives above the transition. Superconductivity persists to much higher dose levels, consistent with fully gapped superconductivity and moderate interband pairing.

Highlights

The interplay between superconductivity and charge-density wave (CDW) in 2H-NbSe2 is not fully understood despite decades of study
The usual mean field picture of a CDW order with rigid amplitude and phase disappearing at TCDW may no longer be valid, as the shortrange CDW order together with a gap in the electronic spectrum has been observed outside the long-range ordered phase[22]
Chatterjee et al.[22] studied the effect of transition-metal doping on the CDW state using angle-resolved photoemission spectroscopy (ARPES), X-ray diffraction, scanning tunneling microscopy (STM), and resistivity, and showed that short-range CDW order with an energy gap survives at high temperatures and high disorder beyond the phase coherence transition

Summary

Introduction

The interplay between superconductivity and charge-density wave (CDW) in 2H-NbSe2 is not fully understood despite decades of study. Suderow et al.[31] proposed a peculiar interplay among SC, CDW order, and Fermi surface complexity, based on the mismatch between the suppression of TCDW at 5 GPa and the maximum Tc at 10.5 GPa. Chatterjee et al.[22] studied the effect of transition-metal doping on the CDW state using ARPES, X-ray diffraction, scanning tunneling microscopy (STM), and resistivity, and showed that short-range CDW order with an energy gap survives at high temperatures and high disorder beyond the phase coherence transition

Methods

Results

Conclusion