Exciton condensation and perfect Coulomb drag

Nandi, Dipanjan; Finck, A. D. K.; Eisenstein, J. P.; Pfeiffer, L. N.; West, K. W.

doi:10.1038/nature11302

Cited by 199 publications

(183 citation statements)

References 25 publications

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“…To search for signatures of correlations between the 2DEG in the GaAs quantum well and the 2D chiral hole fluid 39 in SLG or BLG, we measure the T dependence of the Coulomb drag resistance R D . Experimentally, the Coulomb drag is routinely used as a sensitive probe of strong correlations including transitions to the superconducting state 40 , metal-insulator transitions 41 and Luttinger liquid correlations 42 in quantum wires, and exciton condensation in quantum Hall bilayers 9 . In a Coulomb drag experiment 24,43,44 , a current source is connected to one of the two layers (the active or drive layer).…”

Section: Resultsmentioning

confidence: 99%

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Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

et al. 2014

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Vertical heterostructures combining different layered materials offer novel opportunities for applications and fundamental studies. Here we report a new class of heterostructures comprising a single-layer (or bilayer) graphene in close proximity to a quantum well created in GaAs and supporting a high-mobility two-dimensional electron gas. In our devices, graphene is naturally hole-doped, thereby allowing for the investigation of electron-hole interactions. We focus on the Coulomb drag transport measurements, which are sensitive to many-body effects, and find that the Coulomb drag resistivity significantly increases for temperatures o5-10 K. The low-temperature data follow a logarithmic law, therefore displaying a notable departure from the ordinary quadratic temperature dependence expected in a weakly correlated Fermi-liquid. This anomalous behaviour is consistent with the onset of strong interlayer correlations. Our heterostructures represent a new platform for the creation of coherent circuits and topologically protected quantum bits.

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Section: Resultsmentioning

confidence: 99%

“…Spectacular implications of spontaneous coherence on transport have also been discovered in systems of permanent (interlayer) excitons 7 . Quantum Hall fluids in high-mobility GaAs/AlGaAs semiconductor double quantum wells display a large variety of transport anomalies 8,9 due to spontaneous coherence of interlayer excitons.…”

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confidence: 99%

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

et al. 2014

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“…Indirect exciton and exciton-polariton condensates, created through optical excitation, represent the state-of-the-art with respect to on-demand control of macroscopic coherent states of matter. Coupled layers of two-dimensional electron gas (2DEG) in GaAs quantum wells remain the gold standard in the study of these condensates 71,96 . Van der Waals materials such as graphene and TMDs also offer considerable promise in creating designer condensates.…”

Section: Nature Materials Doi: 101038/nmat5017mentioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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Q uantum materials are on the ascent. This term embodies a vast portfolio of compounds and phenomena where ramifications of quantum mechanics are demonstrably real. Quantum materials are in the vanguard of contemporary physics in part because these systems afford an exceptional venue to uncover the many roles of symmetry, topology, dimensionality and strong correlations in macroscopic observables. Here we set out to explore the ways and means of creating new states of matter in quantum materials and manipulating their phases via external stimuli. Practical control of these properties is a precondition for exploiting quantum advantages in new photonic, electronic and energy technologies, a task of significant societal impact 1 . We will primarily focus on the following classes of quantum materials: transition metal oxides, Fe-and Cu-based high-T c superconductors, van der Waals semiconductors, topological insulators and Weyl semimetals, and, finally, graphene.The properties of quantum materials are anomalously sensitive to external stimuli. In these systems, interactions associated with spin, charge, lattice and orbital degrees of freedom are commonly on par with the electronic kinetic energy. A rather fragile balance between coexisting and competing ground states can be readily shifted via external stimuli, leading to a raft of quantum phases and transitions between them 2,3 . Furthermore, certain classes of driven quantum states (Fig. 1a and Box 1) are explicit products of coherent interaction between light and matter 4-6 . Alternatively, the properties of quantum materials can be pre-programmed by directly manipulating the electronic wavefunction and the attendant Berry phase that give rise to the anomalous velocity of electrons in a solid [7][8][9] . These complementary avenues of controls mean that investigations no longer need to be reduced to merely observing (in contrast, for example, to astrophysics). Instead, it is now feasible to attain, in a predictable fashion, 'properties on demand' by steering a quantum material towards a desirable ground, metastable or transient state. The past decade has witnessed an explosion in the field of quantum materials, headlined by the predictions and discoveries of novel Landau-symmetry-broken phases in correlated electron systems, topological phases in systems with strong spin-orbit coupling, and ultra-manipulable materials platforms based on two-dimensional van der Waals crystals. Discovering pathways to experimentally realize quantum phases of matter and exert control over their properties is a central goal of modern condensed-matter physics, which holds promise for a new generation of electronic/photonic devices with currently inaccessible and likely unimaginable functionalities. In this Review, we describe emerging strategies for selectively perturbing microscopic interaction parameters, which can be used to transform materials into a desired quantum state. Particular emphasis will be placed on recent successes to tailor electronic interaction parameters through th...

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“…: vacuum forces and radiative heat transfer. We show that the giant enhancement is caused by the universal phenomena of coupling between negative and positive frequencies in the near-field and therefore can be used to explain similar effects in acoustic systems [43], hydrodynamic flows [44] and experiments on Coulomb drag [45].…”

Section: Introductionmentioning

confidence: 84%

PT-symmetric spectral singularity and negative-frequency resonance

et al. 2017

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Vacuum consists of a bath of balanced and symmetric positive and negative frequency fluctuations. Media in relative motion or accelerated observers can break this symmetry and preferentially amplify negative frequency modes as in Quantum Cherenkov radiation and Unruh radiation. Here, we show the existence of a universal negative frequency-momentum mirror symmetry in the relativistic Lorentzian transformation for electromagnetic waves. We show the connection of our discovered symmetry to parity-time (PT ) symmetry in moving media and the resulting spectral singularity in vacuum fluctuation related effects. We prove that this spectral singularity can occur in the case of two metallic plates in relative motion interacting through positive and negative frequency plasmonic fluctuations (negative frequency resonance). Our work paves the way for understanding the role of PT -symmetric spectral singularities in amplifying fluctuations and motivates the search for PT -symmetry in novel photonic systems.

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Exciton condensation and perfect Coulomb drag

Cited by 199 publications

References 25 publications

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

Towards properties on demand in quantum materials

PT-symmetric spectral singularity and negative-frequency resonance

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