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arXiv · 2105.05425

Pressure-induced phase switching of the Shubnikov de Haas oscillations in molecular Dirac fermion system $\alpha-$(BETS)$_{2}$I$_{3}$

Yoshitaka Kawasugi·Hikaru Masuda·Masashi Uebe·Hiroshi M. Yamamoto·Reizo Kato·Yutaka Nishio·Naoya Tajima
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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.

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Yoshitaka Kawasugi, Hikaru Masuda, Masashi Uebe, Hiroshi M. Yamamoto, Reizo Kato, Yutaka Nishio, Naoya Tajima. 2021-05-12. Pressure-induced phase switching of the Shubnikov de Haas oscillations in molecular Dirac fermion system $\alpha-$(BETS)$_{2}$I$_{3}$. https://doi.org/10.1103/physrevb.103.205140

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