Three-quarter Dirac points, Landau levels, and magnetization in alpha-(BEDT-TTF)(2)I-3

Article

关键词: ORGANIC CONDUCTOR ALPHA-(BEDT-TTF)(2)I-3;    QUANTIZED HALL CONDUCTANCE;    UNIAXIAL STRAIN;    2-DIMENSIONAL LATTICES;    QUANTUM INTERFERENCE;    HONEYCOMB LATTICE;    BLOCH ELECTRONS;    COUPLED ORBITS;    BREAKDOWN;    DIAMAGNETISM;   

DOI  :  10.1103/PhysRevB.96.085430

来源: SCIE

【 摘 要 】

The energies as a function of the magnetic field (H) and the pressure are studied theoretically in the tight-binding model for the two-dimensional organic conductor alpha-(BEDT-TTF)(2)I-3, in which massless Dirac fermions are realized. The effects of the uniaxial pressure (P) are studied by using the pressure-dependent hopping parameters. The system is semimetallic with the same area of an electron pocket and a hole pocket at P < 3.0 kbar, where the energies (epsilon(0)(D)) at the Dirac points locate below the Fermi energy (epsilon(0)(F)) when H = 0. We find that at P = 2.3 kbar the Dirac cones are critically tilted. In that case a type of band crossing occurs at three-quarter Dirac points; i.e., the dispersion is quadratic in one direction and linear in the other three directions. We obtain magnetic field dependencies of the Landau levels (epsilon(n)): epsilon(n) - e(D)(0) proportional to (nH)(4/5) at P = 2.3 kbar (three-quarter Dirac points) and vertical bar epsilon(n) - epsilon(0)(F)vertical bar proportional to (nH)(2) at P = 3.0 kbar (the critical pressure for the semimetallic state). We also study the magnetization as a function of the inverse magnetic field. We obtain two types of quantum oscillations. One is the usual de Haas-van Alphen (dHvA) oscillation, and the other is the unusual dHvA-like oscillation which is seen even in the system without the Fermi surface.

【 授权许可】

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