[PCP1] Physics and Chemistry1

[PCP1-12] Crystal Growth and Superconducting Properties of Novel NbS₂-based Intercalated Compounds

*Taison Kato¹, Takao Sasagawa¹ (1. Materials and Structures Laboratory, Institute of Science Tokyo (Japan))

Keywords:

New Superconductors,Transition Metal Dichalcogenides,Intercalated Compounds,Single Crystals,Topological Electronic Structures

The layered transition-metal dichalcogenide 2H-NbS₂ is known to be capable of intercalating various elements between its van der Waals layers, which leads to significant changes in its physical properties. Recently, it has been suggested that equimolarly intercalated compounds MNbS₂ (M = In, Bi, and Pb) exhibit superconductivity and have topological electronic structures [1].In this study, we report the results of a systematic exploration of superconductivity in single crystals of NbS₂-based intercalated compounds with the p-block metal elements M = Sn, Sb, Pb, and Bi. Using the chemical vapor transport method with iodine and the flux method with chlorides, we have successfully grown single crystals with various patterns of intercalation, such as equimolar version (SnNbS₂, PbNbS₂, and BiNbS₂), two-thirds-molar version (Bi_2/3NbS₂), and misfit rock-salt version ((SbS)_1.17NbS₂). Their crystal structures, photograph of the grown single crystals, and superconducting transition temperature T_c are summarized in Table 1 (not shown here). X-ray diffraction patterns from the large facet of the obtained crystals were measured. Only the (00L)-reflection peaks were observed, confirming that the large facet of the crystals is the ab-plane. In the case of the Sn system, single crystals of SnNbS₂ were, for the first time, grown and superconductivity was discovered at 1.0 K. Also, for the Pb system, single crystals of PbNbS₂ were successfully grown, and enhanced superconductivity of T_c = 0.9 K, as compared with the previously reported value of 0.1 K [1], was found. Regarding the Bi system, we found that there were two stable intercalated phases, BiNbS₂ and Bi_2/3NbS₂, and succeeded in selectively growing both as single crystals. As a result, Bi_2/3NbS₂, rather than the previously reported BiNbS₂, was found to be a superconductor, and furthermore its T_c was significantly revised from 1.3 K to 3.4 K. In the case of the Sb system, not a single-atomic layer of Sb but a rock-salt-type double-atomic layer of (SbS) was intercalated between the van der Waals layers, forming a so-called misfit compound (SbS)_1.17NbS₂. In this compound, superconductivity was also discovered at 1.2 K in the successfully grown single crystals. For the above new superconductors (SnNbS₂, PbNbS₂, Bi_2/3NbS₂, and (SbS)_1.17NbS₂), the anisotropy of superconducting transitions in magnetic fields and the topological electronic structures elucidated by first-principles calculations will be discussed in detail in the presentation. [1] Bo Zheng et al., Small 20, 2305909 (2024).