{"title":"First-principles LCAO study of the low- and room-temperature phases of CdPS3","authors":"A. Kuzmin","doi":"10.1063/10.0002477","DOIUrl":"https://doi.org/10.1063/10.0002477","url":null,"abstract":"The electronic and atomic structure of a bulk 2D layered van-der-Waals compound CdPS3 was studied in the low (R3) and room (C2/m) temperature phases using first-principles calculations within the periodic linear combination of atomic orbitals method with hybrid meta exchange-correlation M06 functional. The calculation results reproduce well the experimental crystallographic parameters. The value of the indirect band gap Eg=3.4 eV for the room-temperature monoclinic C2/m phase is close to the experimental one, while the indirect band gap Eg=3.3 eV was predicted for the low-temperature trigonal R3 phase. The effect of hydrostatic pressure on the band gap in both phases was studied in the pressure range from 0 to 40 GPa. In both cases, the pressure dependence of the band gap passes through a maximum, but at different pressures. In the R3 phase, the band gap reaches its maximum value of ~4 eV at ~30 GPa, whereas in the C2/m phase, the maximum value of ~3.6 eV is reached already at ~8 GPa.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":"73 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87257747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Origin of anomalous temperature dependence of the Nernst effect in narrow-gap semiconductors","authors":"R. Masuki, T. Nomoto, R. Arita","doi":"10.1103/PHYSREVB.103.L041202","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.L041202","url":null,"abstract":"Based on the Boltzmann transport theory, we study the origin of the anomalous temperature dependence of the Nernst coefficient ($nu$) due to the phonon-drag mechanism. For narrow-gap semiconductors, we find that there are two characteristic temperatures at which a noticeable peak structure appears in $nu$. Contrarily, the Seebeck coefficient ($S$) always has only one peak. While the breakdown of the Sondheimer cancellation due to the momentum-dependence of the electron relaxation time is essential for the peak in $nu$ at low $T$, the contribution of the valence band to the phonon-drag current is essential for the peak at higher $T$. By considering this mechanism, we successfully reproduce $nu$ and $S$ of FeSb$_2$ for which a gigantic phonon-drag effect is observed experimentally.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79592173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Valley pseudospin in monolayer \u0000MoSi2N4\u0000 and \u0000MoSi2As4","authors":"Chen Yang, Z. Song, Xiaotian Sun, Jing Lu","doi":"10.1103/PHYSREVB.103.035308","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.035308","url":null,"abstract":"For a long time, two-dimensional (2D) hexagonal MoS2 was proposed as a promising material for valleytronic system. However, the limited size of growth and low carrier motilities in MoS2 restrict its further application. Very recently, a new kind of hexagonal 2D MXene, MoSi2N4, was successfully synthesized with large size, excellent ambient stability, and considerable hole mobility. In this paper, based on the first-principles calculations, we predict that the valley-contrast properties can be realized in monolayer MoSi2N4 and its derivative MoSi2As4. Beyond the traditional two-level valleys, the valleys in monolayer MoSi2As4 are multiple-folded, implying a new valley dimension. Such multiple-folded valleys can be described by a three-band low-power Hamiltonian. This study presents the theoretical advance and the potential applications of monolayer MoSi2N4 and MoSi2As4 in valleytronic devices, especially multiple information processing.","PeriodicalId":8467,"journal":{"name":"arXiv: Materials Science","volume":"66 5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83571285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}