arXiv subjects

Ryuhei Oka

Publications and source records attributed to Ryuhei Oka.

2 recordsLinked to original sources

arXiv2023

Evidence for three-dimensional Dirac semimetal state in strongly correlated organic quasi-two-dimensional material

The three-dimensional Dirac semimetal is distinct from its two-dimensional counterpart due to its dimensionality and symmetry. Here, we observe that molecule-based quasi-two-dimensional Dirac fermion system, $α$-(BEDT-TTF)$_2$I$_3$, exhibits chiral anomaly-induced negative magnetoresistance and planar Hall effect upon entering the coherent inter-layer tunneling regime under high pressure. Time-reversal symmetry is broken due to the strong electronic correlation effect, while the spin-orbit coupling effect is negligible. The system provides an ideal platform for investigating the chiral anomaly physics by controlling dimensionality and strong electronic correlation.

cond-mat.str-el↗

arXiv2022

Coherent interlayer coupling in quasi-two-dimensional Dirac fermions in $α$-(BEDT-TTF)$_2$I$_3$

Theoretical and experimental studies have supported that the electronic structure of $α$-(BEDT-TTF)$_2$I$_3$ under pressure is described by two-dimensional Dirac fermions. When the interlayer tunneling is coherent, the electronic structure of the system becomes three-dimensional, and we expect the peak structure to appear in the interlayer resistivity under magnetic fields. We theoretically and experimentally show that the peak appears in the interlayer resistivity at low temperatures and high magnetic fields. From the experiment, we estimate that the magnitude of the interlayer tunneling is $t_1 \sim 1$ meV. Our result opens the door to investigating the three-dimensional electronic structure of $α$-(BEDT-TTF)$_2$I$_3$.

cond-mat.str-el↗