Coulomb Drag in the Exciton Regime in Electron-Hole Bilayers

Seamons, John; Morath, Christian P.; Reno, John L.; Lilly, Michael

doi:10.1103/physrevlett.102.026804

Cited by 161 publications

(198 citation statements)

References 31 publications

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“…The onset of spontaneous coherence was evidenced by a strong enhancement of the recombination [25] and tunneling [26] rate, respectively. The results of other transport and optical experiments were also consistent with spontaneous coherence of indirect excitons [24,25,[27][28][29][30][31][32][33]. However, no direct measurement of coherence has been performed in these studies.…”

Section: Spontaneous Coherence Of Excitonssupporting

confidence: 69%

Spontaneous coherence in a cold exciton gas

High¹,

Leonard²,

Hammack³

et al. 2012

Nature

306

307

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Excitons, bound pairs of electrons and holes, form a model system to explore the quantum physics of cold bosons in solids. Cold exciton gases can be realized in a system of indirect excitons, which can cool down below the temperature of quantum degeneracy due to their long lifetimes. Here, we report on the measurement of spontaneous coherence in a gas of indirect excitons. We found that extended spontaneous coherence of excitons emerges in the region of the macroscopically ordered exciton state and in the region of vortices of linear polarization. The coherence length in these regions is much larger than in a classical gas, indicating a coherent state with a much narrower than classical exciton distribution in momentum space, characteristic of a condensate. We also observed phase singularities in the coherent exciton gas. Extended spontaneous coherence and phase singularities emerge when the exciton gas is cooled below a few Kelvin. Spontaneous coherence of excitonsIf bosonic particles are cooled down below the temperature of quantum degeneracy they can spontaneously form a coherent state in which individual matter waves synchronize and combine. Spontaneous coherence of matter waves forms the basis for a number of fundamental phenomena in physics, including superconductivity, superfluidity, and Bose-Einstein condensation (BEC) [1][2][3][4][5]. Spontaneous coherence is the key characteristic of condensation in momentum space [6].Excitons are hydrogen-like bosons at low densities [7] and Cooper-pair-like bosons at high densities [8]. The bosonic nature of excitons allows for condensation in momentum space, i.e. emergence of spontaneous coherence. Designing semiconductor structures with required characteristics and controlling the parameters of the exciton system gives an opportunity to study various types of exciton condensates.A condensate of exciton-polaritons was recently realized in semiconductor microcavities [9][10][11][12][13]. This condensate is characterized by a strong coupling of excitons to the optical field and a short lifetime of the polaritons. Unlike BEC, equilibrium is not required for the polariton condensation and coherence in the polariton condensate forms due to a coherent optical field similar to coherence in lasers [14].There are intriguing theoretical predictions for a range of coherent states in cold exciton systems, including BEC [7], BCS-like condensation [8], charge-density-wave formation [15], and condensation with spontaneous timereversal symmetry breaking [16]. In these condensates, spontaneous coherence of exciton matter waves emerges below the temperature of quantum degeneracy.Since excitons are much lighter than atoms, quantum degeneracy can be achieved in excitonic systems at temperatures orders of magnitude higher than the microKelvin temperatures needed in atomic vapors [1, 2]. Exciton gases need be cooled down to a few Kelvin to enter the quantum regime. Although the temperature of the semiconductor crystal lattice T lat can be lowered well below 1 K in He-refrigerators, lower...

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Section: Spontaneous Coherence Of Excitonssupporting

confidence: 69%

Spontaneous coherence in a cold exciton gas

High¹,

Leonard²,

Hammack³

et al. 2012

Nature

306

307

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“…Finally, we recall that upturns of the Coulomb drag resistivity were reported in e-h doped GaAs/AlGaAs coupled quantum wells [70][71][72] . However, the combination of 2D electron and hole gases in the same GaAs material required a large nanofabrication effort, and the reported magnitude of the drag anomalies was smaller than in our hybrid heterostructures.…”

Section: Discussionmentioning

confidence: 64%

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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“…While qualitatively resembling the upturn observed in electron-hole bilayers Seamons et al, 2009), the theory accounts neither for a subsequent downturn at the lowest temperatures, nor the apparent violation of Onsager reciprocity [although the latter might be related to heating effects ]. The theory also does not make falsifiable predictions regarding the dependence of ρ D on carrier densities in the two layers [at higher temperatures, where the data show the standard T 2 dependence, the density dependence of ρ D is stronger than expected on the basis of the Fermi-liquid many-body calculations (Hwang and Das Sarma, 2008b)].…”

Section: B Interlayer Exciton Formationmentioning

confidence: 80%

“…They have been used to investigate properties of electron-electron scattering in low-density 2D electron systems Kellogg et al, 2002a); signatures of metal-insulator transition in dilute 2D hole systems (Jörger et al, 2000a,b;Pillarisetty et al, 2002Pillarisetty et al, , 2005a; quantum coherence of electrons (Kim et al, 2011;Price et al, 2008Price et al, , 2007 and composite fermions (Price et al, 2010); exciton effects in electron-hole bilayers Keogh et al, 2005;Morath et al, 2009;Seamons et al, 2009); exotic bilayer collective states (Eisenstein, 2014), especially the quantum Hall effect (QHE) at the total filling factor ν T = 1 (Finck et al, 2010;Kellogg et al, 2003Kellogg et al, , 2002bSchmult et al, 2010;Spielman et al, 2004;Tutuc et al, 2009); compressible quantum Hall (QH) states at half-integer filling factor (Muraki et al, 2004;Zelakiewicz et al, 2000); integer QH regime (Lok et al, 2002); Luttinger liquid effects (Debray et al, 2001;Laroche et al, 2008Laroche et al, , 2014; Wigner crystallization in quantum wires (Yamamoto et al, 2002(Yamamoto et al, , 2006(Yamamoto et al, , 2012; and one-dimensional (1D) sub-bands in quasi 1D wires (Debray et al, 2000;Laroche et al, 2011). More generally, interlayer interaction and corresponding transport properties have been studied in hybrid devices comprising a quantum wire and a quantum dot (Krishnaswamy et al, 1999); a SC film and a 2D electron gas (Farina et al, 2004); Si metal-oxide-semiconductor systems …”

Section: Frictional Dragmentioning

confidence: 99%

Coulomb drag

2016

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Coulomb drag is a transport phenomenon whereby long-range Coulomb interaction between charge carriers in two closely spaced but electrically isolated conductors induces a voltage (or, in a closed circuit, a current) in one of the conductors when an electrical current is passed through the other. The magnitude of the effect depends on the exact nature of the charge carriers and microscopic, many-body structure of the electronic systems in the two conductors. Drag measurements have become part of the standard toolbox in condensed matter physics that can be used to study fundamental properties of diverse physical systems including semiconductor heterostructures, graphene, quantum wires, quantum dots, and optical cavities.

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Coulomb Drag in the Exciton Regime in Electron-Hole Bilayers

Cited by 161 publications

References 31 publications

Spontaneous coherence in a cold exciton gas

Spontaneous coherence in a cold exciton gas

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

Coulomb drag

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