Cited by 509Strong Light-Matter InteractionsPlasmonic and Surface Plasmon ResearchSemiconductor Quantum Structures and Devices

The DOI matches its Crossref record; 35 of the 35 references it cites were found in a registry or an index; none of the 13 sources its claims cite is checked for support yet.

Direct Observation of Dirac Cones and a Flatband in a Honeycomb Lattice for Polaritons

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Abstract

Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of honeycomb lattices where the polariton low-energy dispersion is analogous to that of electrons in graphene. Using energy-resolved photoluminescence, we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe p orbital bands, one of them with the nondispersive character of a flatband. The realization of this structure which holds massless, massive, and infinitely massive particles opens the route towards studies of the interplay of dispersion, interactions, and frustration in a novel and controlled environment.

Overview

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TL;DR

The paper reports direct observation of Dirac cones and a flatband in a honeycomb lattice of coupled semiconductor micropillars for polaritons. Energy-resolved photoluminescence reveals graphene-like π/π* bands with Dirac points and higher-energy P bands including a nondispersive flatband.

Key findings

  • The two lowest S bands mimic graphene’s π and π* bands, with six Dirac cones at the corners of the first Brillouin zone; a tight-binding fit gives first- and second-neighbor tunneling \(t = 0.25\) meV and \(t' = -0.02\) meV, and group velocity \(v = 3at/2\hbar = 1.3 \times 10^6\) m/s around the Dirac points.
  • Higher-energy P bands appear above the S bands, separated by \(\Delta E = 3.2\) meV between the two lowest-energy states of individual pillars; the lowest P band is flat, with an infinite effective mass, and the P bands are separated by a gap of about 0.7 meV in Fig. 1(d).
  • Increasing excitation intensity produces polariton condensation at the top of the π* band at the Γ point, with a threshold, single emission line, spatial coherence over the pump spot, and a π phase shift between adjacent pillars.
  • The flatband real-space mode has intensity maxima between pillars arranged in a kagome geometry; a tight-binding model with \(t_\parallel = -1\) meV and \(t_\perp = 0\) meV gives two flat extreme bands, while \(t_\perp = 0.2\) meV makes them dispersive, and an energy-dependent \(t_\perp\) explains the observed lower flat and upper dispersive bands.

Methods

  • Sample: a \(Q = 72000\) λ/2 microcavity with Ga\(_{0.05}\)Al\(_{0.95}\)As layer, 28 top/40 bottom Bragg mirror pairs, twelve 7 nm GaAs quantum wells, 15 meV Rabi splitting, experiments at 10 K and \(-17\) meV cavity-exciton detuning. A honeycomb lattice of coupled micropillars was etched with pillar diameter \(d = 3\) µm and lattice constant \(a = 2.4\) µm; polariton lifetime is 27 ps at the bottom of the lower polariton band, and tunnel coupling is 0.25 meV.
  • Measurements: nonresonant Ti:Sapph laser at 730 nm in a 30 µm spot covering about 30 pillars; energy-resolved photoluminescence collected through a NA = 0.65 objective, dispersed in a spectrometer, and imaged in real or momentum space with a CCD. Low-power excitation probes single-particle physics; a chopper was used at high power to avoid heating.
  • Analysis: tight-binding fits to the measured dispersion, including first- and second-neighbor tunneling; a P-state tight-binding model with \(t_\parallel\) and \(t_\perp\); supplementary 2D Schrödinger and Gross-Pitaevskii simulations.

Limitations

  • The paper states that the highest available excitation density in the experiment prevented observation of the expected modification in the spatial profile when the condensate evolves into a gap soliton.
  • Text-evident: the flatband explanation relies on a phenomenological model in which \(t_\perp\) is assumed to increase with energy, supported by numerical simulations rather than direct measurement of the energy-dependent tunneling.

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Integrity signals

Registry

Crossref · 10.1103/physrevlett.112.116402

Cites

35 of 35 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

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Claims the paper makes

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Show all 54 claims

  • It may state two separate claims as one. 14
  • Probably not a substantial claim. 5
18 of 18
  • The authors state this as an assumption.

    The tunnelling probability of P states is energy dependent, increasing with energy.

    “in which we assume that the tunnelling probability is energy dependent”
    “The band structure reported in Fig. 4(a) can then be understood assuming that t ⊥ increases with the energy”
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Metadata

Authors
Jacqmin, T., Carusotto, I., Sagnes, I., Abbarchi, M., Solnyshkov, D. D., Malpuech, G., Galopin, E., Lemaître, A., Bloch, J., & Amo, A.
Affiliations
  • Centre National de la Recherche Scientifique (FR)
  • University of Trento (IT)
Venue
Physical Review Letters
Published
2014-03-18
Volume
112
Issue
11
Pages
116402-116402
ISSN
  • 0031-9007 (ISSN-L)
  • 1079-7114
OpenAlex
W2043218475
Cited by
509
References
35
Citations by year
2026: 20 · 2025: 24 · 2024: 50 · 2023: 22 · 2022: 44 · 2021: 48 · 2020: 52 · 2019: 35 · 2018: 45 · 2017: 74 · 2016: 39 · 2015: 36 · 2014: 20
FWCI
27.97
Type
journal article
Language
en
Open access
Locations
  • Physical Review Letters (publishedVersion)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • HAL (Le Centre pour la Communication Scientifique Directe) (submittedVersion)
  • INO Open Portal (submittedVersion)
  • Iris (University of Trento) (submittedVersion)
  • arXiv (Cornell University)
Funders
Agence Nationale de la Recherche (ANR-11-BS10-0001, ANR-10-LABX-0035)
Topics
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Strong Light-Matter Interactions
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Plasmonic and Surface Plasmon Research
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Semiconductor Quantum Structures and Devices
Keywords
polaritons, honeycomb lattice, Dirac cones, flat bands, semiconductor microcavities, graphene analogues, massless Dirac equation, band structure engineering

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