Electron–phonon interactions and superconductivity of β -Nb2N thin films

Abstract

Niobium nitride (NbN) has attracted scientific interest due to its diverse physical properties and a variety of structural phases. The structure and superconductivity of the cubic [Formula: see text]-NbN phase are well established, but its hexagonal phases are not explored hitherto. In the present work, we report a simple synthesis route and a detailed study of hexagonal [Formula: see text]-Nb2N thin films. Thermal annealing of sputtered grown [Formula: see text]-NbN leads to a single phase [Formula: see text]-Nb2N at 973 K as confirmed by x-ray diffraction and absorption spectroscopy. The electrical transport measurements revealed a dominance of electron–phonon interactions with a superconducting transition around 4.74 K and an upper critical field [[Formula: see text]] of 3.99 T. The estimated [Formula: see text] is well below the calculated Pauli limit, and the Maki parameter value ([Formula: see text] [Formula: see text] 1) indicates that [Formula: see text] is dominated by an orbital pair breaking effect. Finally, the obtained value of electron–phonon coupling constant ([Formula: see text]) is in excellent agreement with a weak coupling Bardeen–Cooper–Schrieffer value of conventional superconducting materials.

Discovery of Metastable W3P Single Crystals with High Hardness and Superconductivity

“…So far, research about TMLEs that meet both high hardness and superconductivity has mainly been focused on transition-metal borides, − carbides, − and nitrides. − However, the complex overall bonding in transition-metal phosphides (TMPs) with metallic, ionic, and covalent characteristics has brought both opportunities and challenges to the study of hard superconductivity. In recent years, there have been more concerns about the superconductivity of TMPs: possible unconventional superconductivity in MnP, the nodeless superconductivity in the noncentrosymmetric Mo 3 P, and superconductivity in WP with topological structure predicted .…”