Enhancement of superconductivity under pressure and the magnetic phase diagram of tantalum disulfide single crystals.

M. Abdel-Hafiez,B. Pan,J. Zhao,X.-J. Chen,C.-G. Duan,X.-M. Zhao,A. A. Kordyuk,Z. He,Y.-W. Fang

doi:10.1038/srep31824

Abstract

In low-dimensional electron systems, charge density waves (CDW) and superconductivity are two of the most fundamental collective quantum phenomena. For all known quasi-two-dimensional superconductors, the origin and exact boundary of the electronic orderings and superconductivity are still attractive problems. Through transport and thermodynamic measurements, we report on the field-temperature phase diagram in 2H-TaS2 single crystals. We show that the superconducting transition temperature (Tc) increases by one order of magnitude from temperatures at 0.98 K up to 9.15 K at 8.7 GPa when the Tc becomes very sharp. Additionally, the effects of 8.7 GPa illustrate a suppression of the CDW ground state, with critically small Fermi surfaces. Below the Tc the lattice of magnetic flux lines melts from a solid-like state to a broad vortex liquid phase region. Our measurements indicate an unconventional s-wave-like picture with two energy gaps evidencing its multi-band nature.

Highlights

The appearance of superconductivity in 2H-TaS2 in the presence of a charge density wave (CDW) is of great interest
An intrinsic electronic inhomogeneity related to inhomogeneous CDW is quite possible as the chiral CDW reported for this compound supposes a domain structure[4] which is inline with the observed narrowing of the Tc with CDW destruction, for example with doping by Ni14
The authors observed a kink in the pressure dependence of TCDW at about 4 GPa that they attributed to the lock-in transition from an incommensurate CDW to a commensurate CDW

Summary

Transport Measurements

Inhomogeneity is expected to widen the transition of this compound because studies show that even a small concentration of dopants enhance the Tc dramatically[4,14]. This is why superconductivity above 1 K in nominally pure 2H-TaS2 is explained by a small Ta excess or by the presence of sub 1% quantities of impurity atoms[4]. Since in our resistivity experiments we used the lowest current 0.1μA and the ΔTcρ was not sensitive to its small enhancement, we may consider the vortex liquid state as the most probable mechanism of widening the transition, to CuxTiSe215.

Enhancement of Superconductivity Upon Compression

Specific Heat Measurements

Summary

Author Contributions

Findings

Additional Information