Plaquette chirality patterns for robust zero-gap states in $\alpha$-type organic conductor

Abstract

Dirac electrons with a zero-gap state (ZGS) in organic conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$ result from a fine tuning of the seven nearest neighbors transfer integrals ($a_1,a_2,a_3,b_1,b_2,b_3,b_4$) between the four molecules of the unit cell. In this work we show that for given moduli $|a_1|,...|b_4|$, the possibility of having Dirac electron with a ZGS at $3/4$ (or $1/4$) filling strongly depends on the specific configurations of signs of the seven transfer integral. More precisely it is possible to classify the sign configurations into essentially four classes determined by ${\chi }_a=\mathrm{sign}(a_2{a}_3)$ and ${\chi }_b=\mathrm{sign}(b_1{b}_2{b}_3{b}_4)$. Using extended numerics, we show that for both weak and large inhomogeneity in the moduli, the class $({\chi }_a,{\chi }_b)=(-,-)$ is the most favorable to find Dirac electrons with ZGS at $3/4$ (or $1/4$) filling. For the class $({\chi }_a,{\chi }_b)=(+,+)$ in the opposite case, we never found any ZGS at either $1/4$ or $3/4$ filling. The last two classes \suzum{given by} $({\chi }_a,{\chi }_b)=(+,-)$ and $({\chi }_a,{\chi }_b)=(-,+)$ corresponding to an intermediate situation; they allow for ZGS at $3/4$ (resp. $1/4$) filling but are much less favorable than class $({\chi }_a,{\chi }_b)=(-,-)$. As a matter of fact, all previous numerical studies of Dirac electrons and ZGS in $\alpha$-(BEDT-TTF)${}_2$I${}_3$ correspond to class $({\chi }_a,{\chi }_b)=(-,+)$.

arXiv comment14 pages, 9 figs., Proceedings of the International Workshop on Dirac Electrons in Solids 2015

References in corpus (5)

• Topological Insulators with Inversion Symmetry
• Pressure-Induced Zero-Gap Semiconducting State in Organic Conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$ Salt
• Quantum interference from sums over closed paths for electrons on a three-dimensional lattice in a magnetic field: total energy, magnetic moment, and orbital susceptibility
• Analytical solution for the Fermi-sea energy of two-dimensional electrons in a magnetic field: lattice path-integral approach and quantum interference
• Contrast of LiFeAs with isostructural, isoelectronic, and non-superconducting MgFeGe

Cited by in corpus (2)

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