Observation of interband collective excitations in twisted bilayer graphene

Hesp, Niels C. H.; Torre, Iacopo; Rodan-Legrain, Daniel; Novelli, Pietro; Cao, Yuan; Carr, Stephen; Fang, Shiang; Stepanov, Petr; Ruiz, David Barcons; Herzig-Sheinfux, Hanan; Watanabe, Kenji; Taniguchi, Takashi; Efetov, Dmitri K.; Kaxiras, Efthimios; Jarillo‐Herrero, Pablo; Polini, Marco; Koppens, Frank H. L.

doi:10.1038/s41567-021-01327-8

Cited by 71 publications

(59 citation statements)

References 57 publications

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“…In what follows, we use the tunnelling parameters t AB = 20 meV and t AB = 97.5 meV. These parameters were used to simulate the optical properties of TBG in good agreement with a recent TBG experiment [45]. When hBN is aligned with the graphene layers, C 2 symmetry is broken modifying the layer Hamiltonians H l,ζ .…”

Section: Numerical Evaluation Of Plasmon Dispersion In Tbgmentioning

confidence: 85%

Quantum plasmonic non-reciprocity in parity-violating magnets

Arora¹,

Rudner²,

Song³

2022

Preprint

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The optical response of metals is often dominated by plasmonic resonances -the collective oscillations of an interacting electron liquid. Here we unveil a new class of plasmons that arise in a wide range of parity violating magnetic metals. In these materials, broken time reversal and parity symmetries work together with electron-electron interactions to produce intrinsically non-reciprocal bulk plasmons wherein the frequencies of forward and backward moving modes are split. Strikingly, when interactions are strong we find plasmonic non-reciprocity is dominated by the quantum metric dipole that characterizes the real-space profile of Bloch electron wavepackets; in this regime, the quantum metric dipole can give rise to strongly non-reciprocal collective dynamics even when the electronic group velocity is only weakly asymmetric. We anticipate these intrinsic non-reciprocal bulk plasmons can be realized in a wide range of parity violating magnets including twisted bilayer graphene heterostructures where quantum geometric quantities can achieve large values.

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Section: Numerical Evaluation Of Plasmon Dispersion In Tbgmentioning

confidence: 85%

Quantum plasmonic non-reciprocity in parity-violating magnets

Arora¹,

Rudner²,

Song³

2022

Preprint

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“…Despite extensive studies on twisted bilayer graphene, based on transport and scanning techniques, and several interesting theoretical predictions [256][257][258][259][260] , a complete study of its optical properties 261,262 , in particular at low temperatures, where the symmetry-broken states arise is still lacking. In this context, nanophotonics probes like s-SNOM 261,262 and spectroscopy are ideal candidates since they are able to conjugate high spatial resolution (down to ≈ 10nm), with energies that are matching the expected optical features, often in the mid-Infrared or Terahertz (THz) frequency ranges (cf. Figure 7a-b).…”

Section: Moiré Systemsmentioning

confidence: 99%

“…The curved arrows indicate the light impinging on the tip (coming from the laser) as well as the scattered light (going to the detector). Adapted from ref262 . b: 2D plots of the energy loss function L(q, ω) at θ = 1.05°.…”

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confidence: 99%

Quantum Nanophotonics in Two-Dimensional Materials

et al. 2021

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The field of 2D materials-based nanophotonics has been growing at a rapid pace, triggered by the ability to design nanophotonic systems with in-situ control 1 , unprecedented degrees of freedom, and to build material heterostructures from bottom up with atomic precision 2 . A wide palette of polaritonic classes [3][4][5][6] have been identified, comprising ultra-confined optical fields, even approaching characteristic length-scales of a single atom 7 . These advances have been a real boost for the emerging field of quantum nanophotonics, where the quantum mechanical nature of the electrons and/or polaritons and their interactions become relevant. Examples include, quantum nonlocal effects [8][9][10][11] , ultrastrong light-matter interactions [11][12][13][14][15][16] , Cherenkov radiation 13,17,18 , access to forbidden transitions 11 , hydrodynamic effects [19][20][21] , single-plasmon nonlinearities 22,23 , polaritonic quantization 24 , topological effects etc. 3,4 . In addition to these intrinsic quantum nanophotonic phenomena, the 2D material system can also be used as a sensitive probe for the quantum properties of the material that carries the nanophotonics modes, or quantum materials in its vicinity. Here, polaritons act as a probe for otherwise invisible excitations, e.g. in superconductors 25 , or as a new tool to monitor the existence of Berry curvature in topological materials and superlattice effects in twisted 2D materials.In this article, we present an overview of the emergent field of 2D-material quantum nanophotonics, and provide a future perspective on the prospects of both fundamental emergent phenomena and emergent quantum technologies, such as quantum sensing, single-photon sources and quantum emitters manipulation. We address four main implications (cf. Figure 1): i) quantum sensing, featuring polaritons to probe superconductivity and explore new electronic transport hydrodynamic behaviours, ii) quantum technologies harnessing single-photon generation, manipulation and detection using 2D materials, iii) polariton engineering with quantum materials enabled by twist angle and stacking order control in van der Waals heterostructures and iv) extreme light-matter interactions enabled by the strong confinement of light at atomic level by 2D materials, which provide new tools to manipulate light fields at the nano-scale (e.g., quantum chemistry 26 , nonlocal effects, high Purcell enhancement).

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“…In magic-angle twisted trilayer graphene [151,152] the superconducting phase has been explicitly shown to violate the Pauli limit [153], which likely points towards a spin-triplet Cooper pairing. The experimental exploration of collective modes in these materials is still at its infancy [154]. As sample quality increases and tools like cryogenic near-field optical spectroscopy [155,156] become more and more developed, several new types of collective excitations are expected to be discovered and linked with broken symmetry phases of MQM.…”

Section: Solid-state Quantum Simulators Based On Moir é Quantum Mattermentioning

confidence: 99%

Materials and devices for fundamental quantum science and quantum technologies

Polini¹,

Giazotto²,

Fong³

et al. 2022

Preprint

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Technologies operating on the basis of quantum mechanical laws and resources such as phase coherence and entanglement are expected to revolutionize our future. Quantum technologies are often divided into four main pillars: computing, simulation, communication, and sensing & metrology. Moreover, a great deal of interest is currently also nucleating around energy-related quantum technologies. In this Perspective, we focus on advanced superconducting materials, van der Waals materials, and moiré quantum matter, summarizing recent exciting developments and highlighting a wealth of potential applications, ranging from high-energy experimental and theoretical physics to quantum materials science and energy storage.

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Observation of interband collective excitations in twisted bilayer graphene

Cited by 71 publications

References 57 publications

Quantum plasmonic non-reciprocity in parity-violating magnets

Quantum plasmonic non-reciprocity in parity-violating magnets

Quantum Nanophotonics in Two-Dimensional Materials

Materials and devices for fundamental quantum science and quantum technologies

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