Optical Properties of Graphene in Magnetic and Electric fields

Lin, Chiun-Yan; Do, Thi-Nga; Huang, Yao-Kung; Lin, Ming–Fa

doi:10.48550/arxiv.1603.02797

Cited by 3 publications

(1 citation statement)

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“…They are very suitable for exploring the diverse physical, chemical, and material properties. Specifically, the 2D IV-group systems possess the high-symmetry honeycomb lattice and the nano-scaled thickness, in which few-layer graphenes have been verified to exhibit the rich and unique properties, such as the massless/massive fermions [2][3][4][5], the quantized Landau levels [6][7][8][9], the magneto-optical selection rules [10][11][12][13], and the quantum Hall effects [14][15][16][17]. Recently, few-layer germanene, silicene and tinene are, respectively, grown on [Pt(111), Au(111) & Al(111)] surfaces [18][19][20][21], [Ag(111), Ir(111) & ZrBi 2 ] surfaces [22][23][24],…”

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Coulomb scattering rates of excited states in monolayer electron-doped germanene

Shih

Chiu

et al. 2018

Phys. Rev. B

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The excited conduction electrons, conduction holes and valence holes in monolayer germanene exhibit the feature-rich Coulomb decay rates. The dexcitation processes are studied using the Matsubara's screened exchange energy. They might utilize the intraband single-particle excitations (SPEs), the interband SPEs, and three kinds of plasmon modes, depending on the quasiparticle states and the Fermi energies. The low-lying valence holes can decay by the undamped acoustic plasmon, so that they present very fast Coulomb deexcitations, the non-monotonous energy dependence and the anisotropic behavior. However, the low-energy conduction holes and electrons behave as 2D electron gas. The high-energy conduction states and the deep-energy valence ones are similar in the available deexcitation channels and the dependence of decay rate on wave vector k.A lot of two-dimensional (2D) materials have been successfully synthesized since the first discovery of graphene in 2004 using the mechanical exfoliation of Bernal graphite [1]. They are very suitable for exploring the diverse physical, chemical, and material properties. Specifically, the 2D IV-group systems possess the high-symmetry honeycomb lattice and the nano-scaled thickness, in which few-layer graphenes have been verified to exhibit the rich and unique properties, such as the massless/massive fermions [2-5], the quantized Landau levels [6-9], the magneto-optical selection rules [10-13], and the quantum Hall effects [14-17]. Recently, few-layer germanene, silicene and tinene are, respectively, grown on [Pt(111), Au(111) & Al(111)] surfaces [18-21], [Ag(111), Ir(111) & ZrBi 2 ] surfaces [22-24], and Bi 2 Te 3 (111) surface [25]. Such systems possess the buckled structures and the significant spin-orbital couplings (SOCs), leading to the dramatic changes in the essential properties. They are expected to present the unusual Coulomb excitations/deexcitations arising from many-particle electron-electron interactions. The Coulomb scattering rates of the excited states in monolayer germanene is chosen for a model study in this work, especially for their relations with the single-particle and collective electronic excitations. For germanene, silicene and graphene, the low-lying electronic structures mainly arise from the outmost p z orbitals [4, 26]. The Dirac-cone structures, being created by the hexagonal symmetry, might be separated or gapless as a result of the significant/negligible SOCs. The former two are predicted to be narrow-gap semiconductors (E g ∼ 93 meV for Ge & ∼7.9 meV for Si), reflecting the strength of SOC [26]. However, graphene has linear valence and conduction bands intersecting at the Dirac point in the absence of SOC.The predicted band structures could be verified from the angle-resolved photoemission spectroscopy (ARPES) measurements, as done for few-layer germanene grown on Au (111) surface [20]. The experimental observations show that the multiple Dirac-like energy dispersions might be caused by the folding of germanene's Dirac cones. The high-resolution...

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