Plaquette chirality patterns for robust zero-gap states in α-type organic conductor

International Workshop on Dirac Electrons in Solids 2015

Piéchon, Frédéric^1 ; Suzumura, Yoshikazu^2 ; Morinari, Takao^3

Laboratoire de Physique des Solides, CNRS UMR 8502, Université Paris-Sud, Orsay Cedex

F-91405, France^1

Department of Physics, Nagoya University, Chikusa-ku, Nagoya

464-8602, Japan^2

Graduate School of Human and Enviroment Studies, Kyoto University, Kyoto

606-8501, Japan^3

关键词: BEDT-TTF;    Dirac electrons;    Fine tuning;    Gap state;    Inhomogeneities;    Nearest neighbors;    Transfer integral;    Unit cells;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/603/1/012010/pdf
DOI  :  10.1088/1742-6596/603/1/012010

来源: IOP

【 摘 要 】

Dirac electrons with a zero-gap state (ZGS) in organic conductor α-(BEDT- TTF)2I3result from a fine tuning of the seven nearest neighbors transfer integrals (a1,a2,a3,b1,b2,b3,b4) between the four molecules of the unit cell. In this work we show that for given moduli |a11,...|b41, 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 χa= sign(a2a3) and χb= sign(b1b2b3b4). Using extended numerics, we show that for both weak and large inhomogeneity in the moduli, the class (χa,χb) = ( - , - ) is the most favorable to find Dirac electrons with ZGS at 3/4 (or 1/4) filling. For the class (χa,χb) = (+, +) in the opposite case, we never found any ZGS at either 1/4 or 3/4 filling. The last two classes given by (χa,χb) = (+, - ) and (χa,χb) = ( - , +) corresponding to an intermediate situation; they allow for ZGS at 3/4 (resp. 1/4) filling but are much less favorable than class (χa, χb) = ( - , - ). As a matter of fact, all previous numerical studies of Dirac electrons and ZGS in α-(BEDT-TTF)2I3correspond to class (χa,χb) = ( - , +).