Tunneling of quasiparticles between two nearly-aligned graphene sheets produces resonant currentvoltage characteristics because of the quasi-exact conservation of in-plane momentum. We claim that, in this regime, vertical transport in graphene/boron nitride/graphene heterostructures carries precious information on electron-electron interactions and the quasiparticle spectral function of the two-dimensional electron system in graphene. We present extensive microscopic calculations of the tunneling spectra with the inclusion of quasiparticle lifetime effects and elucidate the range of parameters (inter-layer bias, temperature, twist angle, and gate voltage) under which electronelectron interaction physics emerges.
In spite of unscreened Coulomb interactions close to charge neutrality, relativistic massless electrons in graphene allegedly behave as noninteracting particles. A clue to this paradox is that both interaction and kinetic energies scale with particle density in the same way. In contrast, in a dilute gas of nonrelativistic electrons the different scaling drives the transition to Wigner crystal. Here we show that Dirac electrons in a graphene quantum dot with a mass gap localize \`a la Wigner for realistic values of device parameters. Our theoretical evidence relies on many-body observables obtained through the exact diagonalization of the interacting Hamiltonian, which allows us to take all electron correlations into account. We predict that the experimental signatures of Wigner localization are the suppression of the fourfold periodicity of the filling sequence and the quenching of excitation energies, which may be both accessed through Coulomb blockade spectroscopy. Our findings are relevant to other carbon-based nanostructures exhibiting a mass gap.Comment: Revised version accepted for publication in Physical Review
Extreme confinement of electromagnetic waves and mechanical displacement fields to nanometer dimensions through plasmonic nanostructures offers unprecedented opportunities for greatly enhanced interaction strength, increased bandwidth, lower power consumption, chip-scale fabrication, and efficient actuation of mechanical systems at the nanoscale. Conversely, coupling mechanical oscillators to plasmonic nanostructures introduces mechanical degrees of freedom to otherwise static plasmonic structures thus giving rise to the generation of extremely large resonance shifts even for minor position changes. This nanoscale marriage of plasmonics and mechanics has led to the emergence of a new field of study called plasmomechanics that explores the fundamental principles underneath the coupling between light and plasmomechanical nanoresonators. In this review, both the fundamental concepts and applications of plasmomechanics as an emerging field of study are discussed. After an overview of the basic principles of plasmomechanics, the active tuning mechanisms of plasmonic nano-mechanical systems are extensively analyzed. Moreover, the recent developments on the practical implications of plasmomechanic systems for such applications as biosensing and infrared detection are highlighted. Finally, an outlook on the implications of the plasmomechanical nanosystems for development of point-of-care diagnostic devices that can help early and rapid detection of fatal diseases are forwarded.
It is by now well established that high-quality graphene enables a gate-tunable low-loss plasmonic platform for the efficient confinement, enhancement, and manipulation of optical fields spanning a broad range of frequencies, from the mid infrared to the Terahertz domain. While all-electrical detection of graphene plasmons has been demonstrated, electrical plasmon injection (EPI), which is crucial to operate nanoplasmonic devices without the encumbrance of a far-field optical apparatus, remains elusive. In this work, we present a theory of EPI in double-layer graphene, where a vertical tunnel current excites acoustic and optical plasmon modes. We first calculate the power delivered by the applied inter-layer voltage bias into these collective modes. We then show that this system works also as a spectrally-resolved molecular sensor. arXiv:1811.00460v1 [cond-mat.mes-hall] 1 Nov 2018
We propose a protocol to identify spatial hallmarks of viscous electron flow in graphene and other two-dimensional viscous electron fluids. We predict that the profile of the magnetic field generated by hydrodynamic electron currents flowing in confined geometries displays unambiguous features linked to whirlpools and backflow near current injectors. We also show that the same profile sheds light on the nature of the boundary conditions describing friction exerted on the electron fluid by the edges of the sample. Our predictions are within reach of vector magnetometry based on nitrogen-vacancy centers embedded in a diamond slab mounted onto a graphene layer.
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