Exploring control of the emergent exciton insulator state in 1T-TiSe$_2$ monolayer by state-of-the-art theory models
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arXiv
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| Format: | Preprint |
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2024
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| _version_ | 1866913417916317696 |
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| author | Tang, Hong Yin, Li Csonka, Gábor I. Ruzsinszky, Adrienn |
| author_facet | Tang, Hong Yin, Li Csonka, Gábor I. Ruzsinszky, Adrienn |
| contents | The layered transition metal dichalcogenide 1T-TiSe$_2$ is of great research interest, having intriguing properties of charge density waves (CDW) and superconductivity under doping or pressurizing. The monolayer form of 1T-TiSe$_2$ also shows a CDW with a higher transition temperature T_c than the bulk, indicating a stronger CDW interaction. By using the meta-generalized gradient approximation (metaGGA)-based model Bethe-Salpeter Equation (BSE) and many-body perturbation GW+BSE methods, we calculate the exciton binding energies and electron energy loss spectrum (EELS) for the 1T-TiSe$_2$ monolayer under different in-plane biaxial strains. We find that even without strain the 1T-TiSe$_2$ monolayer can have negative exciton energies at the Brillouin zone boundary point M, with a binding energy larger than the gap. The calculated EELS reinforces this picture, indicating EI (exciton insulator) states in 1T-TiSe$_2$ monolayer even without strain. The Wannier-Mott formula calculations of exciton binding energy corroborate results from GW+BSE. Small compressive strains enhance the EI state, and for tensile strains slightly less than 3%, the EI state in this monolayer persists. At large tensile strains, the material makes a transition to a normal semiconductor. Our results provide important information for understanding the quantum nature of this two-dimensional (2D) material. Our results from the standard G0W0@PBE+SOC+U+BSE approach are not qualitatively different from those of a more computationally efficient metaGGA-based SCAN+SOC+U+mBSE+$f_{xc}^{loc}$ approach that employs a model BSE. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_04033 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Exploring control of the emergent exciton insulator state in 1T-TiSe$_2$ monolayer by state-of-the-art theory models Tang, Hong Yin, Li Csonka, Gábor I. Ruzsinszky, Adrienn Computational Physics The layered transition metal dichalcogenide 1T-TiSe$_2$ is of great research interest, having intriguing properties of charge density waves (CDW) and superconductivity under doping or pressurizing. The monolayer form of 1T-TiSe$_2$ also shows a CDW with a higher transition temperature T_c than the bulk, indicating a stronger CDW interaction. By using the meta-generalized gradient approximation (metaGGA)-based model Bethe-Salpeter Equation (BSE) and many-body perturbation GW+BSE methods, we calculate the exciton binding energies and electron energy loss spectrum (EELS) for the 1T-TiSe$_2$ monolayer under different in-plane biaxial strains. We find that even without strain the 1T-TiSe$_2$ monolayer can have negative exciton energies at the Brillouin zone boundary point M, with a binding energy larger than the gap. The calculated EELS reinforces this picture, indicating EI (exciton insulator) states in 1T-TiSe$_2$ monolayer even without strain. The Wannier-Mott formula calculations of exciton binding energy corroborate results from GW+BSE. Small compressive strains enhance the EI state, and for tensile strains slightly less than 3%, the EI state in this monolayer persists. At large tensile strains, the material makes a transition to a normal semiconductor. Our results provide important information for understanding the quantum nature of this two-dimensional (2D) material. Our results from the standard G0W0@PBE+SOC+U+BSE approach are not qualitatively different from those of a more computationally efficient metaGGA-based SCAN+SOC+U+mBSE+$f_{xc}^{loc}$ approach that employs a model BSE. |
| title | Exploring control of the emergent exciton insulator state in 1T-TiSe$_2$ monolayer by state-of-the-art theory models |
| topic | Computational Physics |
| url | https://arxiv.org/abs/2407.04033 |