Pressure-induced phase switching of the Shubnikov de Haas oscillations in molecular Dirac fermion system $\alpha -$(BETS)${}_2$I${}_3$

Abstract

We report on the Shubnikov de Haas (SdH) oscillations in the quasi two-dimensional molecular conductor $\alpha -$(BETS)${}_2$I${}_3$ [BETS: bis(ethylenedithio)tetraselenafulvalene] laminated on polyimide films at 1.7 K. From the SdH phase factor, we verified experimentally that the material is in the Dirac fermion phase under pressure. $\alpha -$(BETS)${}_2$I${}_3$ is in the vicinity of the phase transition between strongly correlated insulating and Dirac fermion phases, and is a possible candidate for an ambient-pressure molecular Dirac fermion system. However, the SdH oscillations indicate that the Berry phase is zero at ambient pressure. Under pressure, a $\pi$ Berry phase emerges when the metal-insulator crossover is almost suppressed at $\sim$0.5 GPa. The results contrast those for the pioneering molecular Dirac fermion system $\alpha -$(BEDT-TTF)${}_2$I${}_3$ [BEDT-TTF: bis(ethylenedithio)tetrathiafulvalene] in which Dirac fermions and semiconducting behavior are simultaneously observed.

12 pages, 10 figures, including Supplemental Material

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Cited by in corpus (8)

• Interaction-induced quantum spin Hall insulator in the organic Dirac electron system $\alpha$-(BEDT-TSeF)${}_2$I${}_3$
• Gap opening mechanism for correlated Dirac electrons in organic compounds $\alpha$-(BEDT-TTF)${}_2$I${}_3$ and $\alpha$-(BEDT-TSeF)${}_2$I${}_3$
• Correlation-driven organic 3D topological insulator with relativistic fermions
• Electric and Magnetic Responses of Two-dimensional Dirac Electrons in Organic Conductor $\alpha$-(BETS)${}_2$I${}_3$
• Three-Dimensional Topological Semimetal/Insulator States in α-Type Organic Conductors with Interlayer Spin-Orbit Interaction
• Crossover in Electronic Specific Heat near Narrow-Sense Type-III Dirac Cones
• 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
• Hofstadter Butterfly and Broken-Symmetry Quantum Hall States in α-Type Organic Dirac Fermion Systems