Superconductivity in a misfit layered compound (SnSe)$_{1.16}$(NbSe$_2$)

TL;DR

This study reports the discovery of superconductivity at 3.4 K in a misfit layered compound (SnSe)$_{1.16}$(NbSe$_2$), highlighting its structural features and superconducting properties.

Contribution

First observation of superconductivity in (SnSe)$_{1.16}$(NbSe$_2$), with detailed analysis of its structure and superconducting parameters.

Findings

Superconductivity with $T_c$ of 3.4 K was observed.

The compound exhibits multi-band superconductivity.

The upper critical field exceeds the Pauli limit slightly.

Abstract

The large size single crystals of (SnSe)$_{1.16}$(NbSe$_2$) misfit layered compound were grown and superconductivity with $T_c$ of 3.4 K was first discovered in this system. Powder X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) clearly display the misfit feature between SnSe and NbSe$_2$ subsystems. The Sommerfeld coefficient $\gamma$ inferred from specific-heat measurements is 16.73 mJ mol$^{-1}$ K$^{-2}$, slightly larger than the usual misfit compounds. The normalized specific heat jump $\Delta$$C_e$/$\gamma$$T_{\rm c}$ is about 0.98, and the electron-phonon coupling constant $\lambda$$_{e-ph}$ is estimated to be 0.80. The estimated value of the in-plane upper critical magnetic field, $H_{c2}^{ab}$(0), is about 7.82 T, exceeding the Pauli paramagnetic limit slightly. Both the specific-heat and $H_{c2}$ data suggest that (SnSe)$_{1.16}$(NbSe$_2$) is a multi-band superconductor.