Tunable Excitons in Biased Bilayer Graphene

Park, Cheol-Hwan; Louie, Steven G.

doi:10.1021/nl902932k

Cited by 99 publications

(119 citation statements)

References 54 publications

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“…As expected, the absorption onset displays a blueshift as the electric field increases the band gap magnitude. Meanwhile, the prominent absorption feature is gradually broadened and split into a double-peak structure (I 1 and I 2 ) which stems from the two one-dimensional-like von-Hove singularities 19,30 at opposite "Mexican-hat brims" (Fig. 1 (a)), which is consistent with previous DFT results 25 .…”

Section: Quasiparticle Band Gap Of Gblgsupporting

confidence: 90%

“…This tunable energy difference can surely affect the thermal population of exciton states and their luminescent performance. The tunability of the order of exciton energies is in qualitative agreement with previous tight-binding studies 19 .…”

Section: Dark and Bright Excitonssupporting

confidence: 90%

“…The binding energy vary significantly with the gate voltage. They are 35, 54, 76 and 80meV under four sampling voltages, respectively, fairly close to previous tight-binding calculations 19 . Also remarkably, these peak positions are in excellent agreement with the previous infrared mi- crospectroscopy experiment 9 as shown in Fig.…”

Section: Quasiparticle Band Gap Of Gblgsupporting

confidence: 90%

“…Tight-binding models 19 have revealed appealing properties of excitons in GBLG, but it must rely on parameters. In particular, recent ab initio GW-BSE simulation has successfully predicted enhanced many-electron effects on intrinsic graphene 20 , which are confirmed by subsequent experiments [21][22][23] .…”

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Quasiparticle energy and optical excitations of gated bilayer graphene

Liang

Yang

2012

Phys. Rev. B

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By employing the first-principles GW-Bethe-Salpeter Equation (BSE) simulation, we obtain the accurate quasiparticle (QP) band gap and optical absorption spectra of gated bilayer graphene (GBLG). Enhanced electron-electron interactions dramatically enlarge the QP band gap; infrared optical absorption spectra are dictated by bright bound excitons. In particular, the energies of these excited states can be tuned in a substantially wider range, by the gate field, than previous predictions. Our results clearly explain recent experiments and satisfactorily resolve the inconsistency between experimentally measured transport and optical band gaps. Moreover, we predict that the most deeply bound exciton is a dark exciton which is qualitatively different from the hydrogenic model, and its electron and hole are condensed onto opposite graphene layers, respectively. This unique dark exciton shall not only impact the exciton dynamics but also provide an exciting opportunity to study entangling exchange effects of many-body physics.

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Section: Quasiparticle Band Gap Of Gblgsupporting

confidence: 90%

Section: Dark and Bright Excitonssupporting

confidence: 90%

Section: Quasiparticle Band Gap Of Gblgsupporting

confidence: 90%

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confidence: 99%

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Quasiparticle energy and optical excitations of gated bilayer graphene

Liang

Yang

2012

Phys. Rev. B

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“…The size of the gap is then limited by the strength of interlayer tunneling in the bilayer. The excitons of this semiconductor are unusual 9,11,[24][25][26][27] because of the Berry phase properties graphene's two-dimensional Dirac model states and are in this sense similar to the excitons of a topological insulator 28 . The properties of optically excited populations of bilayer graphene excitons which have thermalized and condensed have been studied in previous 25 theoretical work.…”

Section: Introductionmentioning

confidence: 99%

Spatially indirect exciton condensate phases in double bilayer graphene

MacDonald

2017

Phys. Rev. B

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We present a theory of spatially indirect exciton condensate states in systems composed of a pair of electrically isolated Bernal graphene bilayers. The ground state phase diagram in a two-dimensional displacement-field/inter-bilayer-bias space includes layer-polarized semiconductors, spin-density-wave states, exciton condensates, and states with mixed excitonic and spin order. We find that two different condensate states, distinguished by a chirality index, are stable under different electrical control conditions.

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Theory and Ab Initio Calculation of Optically Excited States—Recent Advances in 2D Materials

Xie

Cao

2019

Advanced Materials

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Over the past decade, the research on these materials systems from both theoretical and experimental exploration has produced many fascinating results, such as the discovery of strongly bound two-and three-particle excited states [12][13][14][15][16][17][18][19][20][21] as well as their time-and spindependent dynamics. [22,23] This review will have three parts. In the first part after this introduction, we will discuss several theoretical and computational methods for the excited-state problems. These methods will be introduced pedagogically and will be accessible to both theoretical and experimental readers. In the second part, we will focus on selected 2D materials systems and defect systems that demonstrate interesting properties related to the optically excited states. We present the understanding of these optically excited states by using the methods introduced in the first part. The last part will conclude this review paper and will include an outlook section that highlights several future opportunities in the development of the theory on the optically excited states.The aim of this review is to provide a survey and pedagogical introduction of various theoretical tools and their applications in the optically excited states of low-dimensional materials systems, rather than to scrutinize a specific theoretical approach or a specific materials system in depth. We will also discuss the key differences in the excited-state properties of materials at different dimensions. The physical origin of this difference will be elucidated from the aspects of many-particle interactions, dimensionality effects, spatial symmetry, and tunability. Interested readers may also refer to the review papers about the electronic valley degree of freedom and the valley-spin locking, [22,24] about optical properties in various 2D materials, [5,23,25,26] about excited states in heterostructures, [27][28][29] about photonics, and optoelectronics using 2D materials. [10,30,31] Apart from the optically excited states which are essentially electronic quasiparticle excitation, many other forms of excited states, such as the phonon, plasmon, and magnon excitations, have demonstrated unique and interesting features in 2D materials. [32][33][34] For example, recent theoretical studies of the phonon transport in graphene and other atomic layered materials have discovered hydrodynamic behavior which is distinct from the kinetic phonon-transport behavior in conventional 3D materials at room temperature. [35,36] However, instead of being comprehensive and covering all aspects of the excited-state research, this review will focus on the electronic excited states that Recent studies of the optical properties of 2D materials have reported unique phenomena and features that are absent in conventional bulk semiconductors. Many of these interesting properties, such as enhanced light-matter coupling, gate-tunable photoluminescence, and unusual excitonic optical selection rules arise from the nature of the two-and multi-particle excited states such as stron...

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Tunable Excitons in Biased Bilayer Graphene

Cited by 99 publications

References 54 publications

Quasiparticle energy and optical excitations of gated bilayer graphene

Quasiparticle energy and optical excitations of gated bilayer graphene

Spatially indirect exciton condensate phases in double bilayer graphene

Theory and Ab Initio Calculation of Optically Excited States—Recent Advances in 2D Materials

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