Dresden 2020 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 15: Graphene (jointly with DY, MA, HL, DS, O) (joint session TT/DY/HL)

HL 15.1: Talk

Monday, March 16, 2020, 15:00–15:15, HSZ 201

Edge state crossing behaviour in a multi-band tight-binding model of graphene — •Thorben Schmirander, Marta Prada, and Daniela Pfannkuche — I. Institut für theoretische Physik Universität Hamburg, Hamburg, Deutschland

The description of Dirac electrons in the band structure of graphene is commonly performed using effective tight binding models [1]. These effective models use single-orbital Hamiltonians with modified hopping parameters in order to account for the influence of the higher energy orbitals in graphene. We go beyond such effective models by including d-orbitals in an atomistic tight-binding model. The inclusion of the d-orbitals results in a breaking of electron-hole symmetry which in turn changes the dispersion of the states around the Fermi energy. When considering a finite graphene sample, edge states occur, which cross the band gap and connect the Dirac cones at the K and K’ point. These edge states are the key to the topological properties of graphene, because they may exhibit the Spin Hall effect [3]. The band gap crossing is discussed by comparing different expectation values computed from the edge states. These expectation values change under different influences, such as strain or an external electric field. Apart from qualitatively treating these influences on the crossing of the band gap, electron-electron interactions are included via a self-consistent mean-field approach.

[1] van Miert, G., Juricic, V. and Morais Smith, C. Phys. Rev. B 90 195414 (2014)

[2] van Gelderen, R. and Morais Smith, C., Phys. Rev. B 81 125435 (2010)

[3] Kane, C. L . and Mele, E. J., Phys. Rev. Lett. 95, 226801 (2005)