Superconductivity in the metastable 1 T' and 1 T'″ phases of Mo S2 crystals
Abstract
Transition-metal dichalcogenides open novel opportunities for the exploration of exciting new physics and devices. As a representative system, 2 H -MoS2 has been extensively investigated owing to its unique band structure with a large band gap, degenerate valleys, and nonzero Berry curvature. However, experimental studies of metastable 1 T polytypes have been a challenge for a long time, and electronic properties are obscure due to the inaccessibility of single phase without the coexistence of 1 T' , 1 T″ , and 1 T'″ lattice structures, which hinder the broad applications of Mo S2 in future nanodevices and optoelectronic devices. Using Kx(H2O)yMo S2 as the precursor, we have successfully obtained high-quality layered crystals of the metastable 1 T'″-MoS2 with √{3 }a ×√{3 }a superstructure and metastable 1 T'-MoS2 with a ×2 a superstructure, as evidenced by structural characterizations through scanning tunneling microscopy, Raman spectroscopy, and x-ray diffraction. It is found that the metastable 1 T'-MoS2 is a superconductor with onset transition temperature (Tc) of 4.2 K, while the metastable 1 T'″-MoS2 shows either superconductivity with Tc of 5.3 K or insulating behavior, which strongly depends on the synthesis procedure. Both of the metastable polytypes of Mo S2 crystals can be transformed to the stable 2 H phase with mild annealing at about 70 °C in He atmosphere. These findings provide pivotal information on the atomic configurations and physical properties of 1 T polytypes of Mo S2 .
- Publication:
-
Physical Review B
- Pub Date:
- November 2018
- DOI:
- 10.1103/PhysRevB.98.184513
- arXiv:
- arXiv:1809.09298
- Bibcode:
- 2018PhRvB..98r4513S
- Keywords:
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- Condensed Matter - Superconductivity;
- Condensed Matter - Materials Science
- E-Print:
- 17 pages, 4 figures