Novel properties of two-dimensional Janus transition metal hydrosulfides: electride states, charge density waves and superconductivity

Abstract

Inspired by recent experimental synthesis of the two-dimensional Janus material MoSH, we have performed extensive first-principles calculations to investigate the characteristics of all possible Janus two-dimensional transition metal hydrosulfides (JTMSHs), in both the 2H and 1T phases. Our investigations revealed that the JTMSHs can form a unique family of two-dimensional materials with intriguing physical and chemical properties. In details, we have found that JTMSHs can exist in various states, exhibiting metallic, semiconducting, and magnetic character. One particularly intriguing finding considered identification of electride states with distinct bonding characteristics in the 2H-JTMSHs for TM=V, Nb, Ta, Mo, W and Tc. Additionally, we have observed evidence of charge density wave scenario in 1T-JTMSH with TM=Tc, Re, and W and 2H-JTMSH with TM = Tc. Importantly, by applying compressive strain to these materials, the charge density wave can be completely suppressed, eventually leading to the superconducting phase. In particular, we have shown that when subjected to a compressive strain within 10%, the superconducting transition temperature (TC) of 1T-WSH, 1T-TcSH and 2H-TcSH can reach values of 13.8, 16.2 and 24.2 K respectively. Moreover, our investigation also unveiled two intrinsic phonon-mediated superconductors, namely 2H-WSH and 1T-RuSH with TC of 17.0 and 8 K, respectively.