First-principles study of the effective Hamiltonian for Dirac fermions with spin-orbit coupling in two-dimensional molecular conductor $\alpha$-(BETS)${}_2$I${}_3$

Abstract

We employed first-principles density-functional theory (DFT) calculations to characterize Dirac electrons in quasi-two-dimensional molecular conductor $\alpha$-(BETS)${}_2$I${}_3$ [= $\alpha$-(BEDT-TSeF)${}_2$I${}_3$] at a low temperature of 30K. We provide a tight-binding model with intermolecular transfer energies evaluated from maximally localized Wannier functions, where the number of relevant transfer integrals is relatively large due to the delocalized character of Se $p$ orbitals. The spin-orbit coupling gives rise to an exotic insulating state with an indirect band gap of about 2 meV. We analyzed the energy spectrum with a Dirac cone close to the Fermi level to develop an effective Hamiltonian with site-potentials, which reproduces the spectrum obtained by the DFT band structure.

arXiv commentThe manuscript has been accepted for publication in the European Physical Journal B on Dec. 15th, 2020

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• Electric and Magnetic Responses of Two-dimensional Dirac Electrons in Organic Conductor $\alpha$-(BETS)${}_2$I${}_3$
• Seebeck Effect of Dirac Electrons in Organic Conductors under Hydrostatic Pressure Using a Tight-Binding Model Derived from First Principles
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• Conductivity of Two-dimensional Dirac Electrons Close to Merging in Organic Conductor $\alpha$-STF${}_2$I${}_3$ at Ambient Pressure
• Three-Dimensional Topological Semimetal/Insulator States in α-Type Organic Conductors with Interlayer Spin-Orbit Interaction
• Observations of $\nu =1$ Quantum Hall Effect and Inter-Band Effects of Magnetic fields on Hall Conductivity in Organic Massless Dirac Fermion System $\alpha$-(BETS)${}_2$I${}_3$ under Pressure
• Spin-Orbit Coupling Effect on the Seebeck Coefficient in Dirac Electron Systems in $\alpha$-(BETS)${}_2$I${}_3$
• Wannier Center Analysis on Possible Three-Dimensional Topological Phases in α-Type Layered Organic Conductors