Abstract
Transition metal phosphorous trichalcogenides, ( and being transition metal and chalcogen elements, respectively), have been the focus of substantial interest recently because they are unusual candidates undergoing Mott transition in the two-dimensional limit. Here we investigate material properties of the compounds with and Ni employing ab initio density functional and dynamical mean-field calculations, especially their electronic behavior under external pressure in the paramagnetic phase. Mott metal-insulator transitions (MIT) are found to be a common feature for both compounds, but their lattice structures show drastically different behaviors depending on the relevant orbital degrees of freedom, i.e., or . Under pressure, can undergo an isosymmetric structural transition within monoclinic space group by forming Mn-Mn dimers due to the strong direct overlap between the neighboring orbitals, accompanied by a significant volume collapse and a spin-state transition. In contrast, and , with their active orbital degrees of freedom, do not show a structural change at the MIT pressure or deep in the metallic phase within the monoclinic symmetry. Hence and become rare examples of materials hosting electronic bandwidth-controlled Mott MITs, thus showing promise for ultrafast resistivity switching behavior.
- Received 27 August 2018
- Revised 17 September 2019
DOI:https://doi.org/10.1103/PhysRevLett.123.236401
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