SnTaS₂: Where Topology Meets Superconductivity
Condensed matter physics plays a central role in modern science and technology by exploring how electrons behave collectively within materials. Advances in this field have enabled the development of semiconductors, magnetic storage devices, sensors and superconducting technologies that underpin modern electronics. More recently, quantum materials such as topological semimetals and superconductors have attracted considerable attention because they exhibit novel electronic states arising from the interplay of symmetry, topology and electron correlations.
Topology, a branch of mathematics concerned with properties that remain unchanged under continuous deformations, has emerged as a powerful concept in condensed matter physics. In quantum materials, topology gives rise to electronic states that are protected against impurities, defects and other perturbations, making them remarkably robust. This has led to the discovery of topological insulators, Dirac and Weyl semimetals and nodal-line semimetals, all of which exhibit unconventional electronic properties.
When topology coexists with superconductivity, it can potentially generate exotic quasiparticles such as Majorana modes, which are considered promising building blocks for fault-tolerant quantum computation. Consequently, understanding the interplay between topology and superconductivity has become one of the most active and exciting areas of contemporary condensed matter research.
Investigating the Superconducting Properties of SnTaS₂
In this context, the synthesis and characterisation of high-quality single crystals of the nodal-line semimetal SnTaS₂ are presented. SnTaS₂ belongs to the family of intercalated transition-metal dichalcogenides and was grown using the chemical vapour transport method. The residual resistive ratio comes out to be ~530 with no signatures of structural phase transition. The onset resistive critical temperature is found to be 2.9±0.1 K. The upper critical field Hc2,c fits very well with GL fit while Hc2,ab shows upward behaviour near Tc. Anisotropy factor is estimated to be 3.1.
SnTaS2 is an orbital-limited weakly coupled Type-II superconductor. Magneto-transport measurements show a non-saturating MR of 320% at 5K up to ±5 Tesla. We observe Weak Anti Localisation (WAL) effect at low fields, which is the first ever experimental confirmation of WAL in SnTaS2. In essence, SnTaS2 provides a good platform for understanding the superconducting transition metal dichalcogenides with nodal-line fermions. A lot about the pairing symmetry in the superconducting state as well as the topological feature, needs to be unravelled in this superconducting system.