High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

Berman, Oleg L.; Kezerashvili, Roman Ya.

doi:10.1103/physrevb.93.245410

Cited by 90 publications

(94 citation statements)

References 84 publications

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“…In a bilayer or a bulk system, a strong spin-layer locking exists 2–5 . Owing to this effect together with a weak van der Waals interlayer interaction, strongly confined electrons and holes might exist within different layers of a multilayer TMDC (interlayer excitons 6–9 ), even without the requirement of a spacer layer 10, 11 . Interlayer excitons are potential candidates for unraveling a wealth of interesting physical phenomena, such as Bose-Einstein condensation, high temperature superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect 10–15 .…”

Section: Introductionmentioning

confidence: 99%

“…Interlayer excitons have been successfully created in coupled GaAs quantum wells at cryogenic temperatures 16 . In contrast, TMDCs hold the promise for observing aforementioned phenomena at much higher temperatures 10, 11 . In TMDCs, interlayer excitons have been created in artificial heterostructures by stacking monolayers of two different TMDC materials on top of each other 6–9 .…”

Section: Introductionmentioning

confidence: 99%

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Interlayer excitons in a bulk van der Waals semiconductor

et al. 2017

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Bound electron–hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose–Einstein condensation, superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers. By combining high-field magneto-reflectance experiments and ab initio calculations for 2H-MoTe2, we explain their salient features: the positive sign of the g-factor and the large diamagnetic shift. Our investigations solve the long-standing puzzle of positive g-factors in transition metal dichalcogenides, and pave the way for studying collective phenomena in these materials at elevated temperatures.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interlayer excitons in a bulk van der Waals semiconductor

et al. 2017

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“…At large interlayer separations D, the exchange effects in the exciton-exciton interactions in a phosphorene double layer can be neglected, since the exchange interactions in a spatially separated electron-hole system in a double layer are suppressed due to the low tunneling probability, caused by the shielding of the dipoledipole interaction by the insulating barrier [6,40]. Therefore, we treat the dilute system of dipolar excitons in a phosphorene double layer as a weakly interacting Bose gas.…”

Section: Collective Excitations For Dipolar Excitons In a Black mentioning

confidence: 99%

“…Due to relatively large exciton binding energies in novel 2D semiconductors, the BEC and superfluidity of dipolar excitons in double layers of transition metal dichalcogenides (TMDCs) was studied [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Superfluidity of dipolar excitons in a transition metal dichalcogenide double layer

Berman

Kezerashvili

2017

Phys. Rev. B

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We study the formation of dipolar excitons and their superfluidity in a black phosphorene double layer. The analytical expressions for the single dipolar exciton energy spectrum and wave function are obtained. It is predicted that a weakly interacting gas of dipolar excitons in a double layer of black phosphorus exhibits superfluidity due to the dipole-dipole repulsion between the dipolar excitons. In calculations are employed the Keldysh and Coulomb potentials for the interaction between the charge carriers to analyze the influence of the screening effects on the studied phenomena. It is shown that the critical velocity of superfluidity, the spectrum of collective excitations, concentrations of the superfluid and normal component, and mean field critical temperature for superfluidity are anisotropic and demonstrate the dependence on the direction of motion of dipolar excitons. The critical temperature for superfluidity increases if the exciton concentration and the interlayer separation increase. It is shown that the dipolar exciton binding energy and mean field critical temperature for superfluidity are sensitive to the electron and hole effective masses. The proposed experiment to observe a directional superfluidity of excitons is addressed.

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“…The pairing was registered in double quantum well AlGaAs heterostructures in the quantum Hall state under study of their transport properties [25][26][27][28]. The possibility of electronhole pairing was also considered with reference to topological insulator heterostructures [29][30][31][32], double bilayer graphene [33], double few-layer graphene [34], transition metal dichalcogenide [35][36][37] and black phosphorene [38] double layers. Recently several experimental efforts to register electron-hole pairing in double layer graphene systems were done [39][40][41][42], but the results of these experiments are controversial.…”

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confidence: 99%

Strong enhancement of third-harmonic generation in a double layer graphene system caused by electron-hole pairing

Germash

Fil

2017

EPL

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-A manifestation of electron-hole pairing in nonlinear electromagnetic response of a double layer graphene system is studied. It is shown that the pairing causes the appearance of a number of peaks in the frequency dependence of the intensity of the third harmonic generation (THG). The highest peak corresponds to ω = (2/3)∆, where ω is the incident wave frequency, and ∆ is the order parameter of the electron-hole pairing. The absolute value of the THG intensity in the systems with electron-hole pairing is in several orders of magnitude greater than the THG intensity in the unpaired state. It is shown that huge enhancement of the THG intensity occurs both in the double monolayer and double bilayer graphene systems.Introduction. -Nonlinear optical and microwave properties of graphene attract considerable attention. Strong nonlinear response of graphene can be seen from the classical equation of motion for a charged particle with the spectrum linear in the momentum [1,2]. This equation yields the electric current that contains all odd Fourier harmonics with the amplitudes falling down very slowly with the harmonic number. The quantum approach [3][4][5][6][7] predicts resonant behavior for the third harmonic generation in graphene. The frequency dependence of the THG intensity has the main peak at ω = (2/3)ε F and two minor peaks at ω = ε F and ω = 2ε F , where ε F is the Fermi energy. Nonlinear optical effects in graphene systems were observed experimentally. In [8] the coherent nonlinear optical response of single-and few-layer graphene was measured using four-wave mixing. Sharp contrast images of graphene flakes on a dielectric substrate at combined frequencies were observed. Graphene with the effective thickness 3Å demonstrates the nonlinear emission intensity in 10 times larger than a 4 nm gold film. Nonlinear susceptibility at the wavelength λ ≈ 1 µm is evaluated as large as 10 −7 esu. In the THG experiment [9] the effective nonlinear susceptibility χ (3) ∼ 5 · 10 −9 esu at the incident wavelength λ i = 1.7 µm was registered. Strong THG in a monolayer graphene on an amorphous silica substrate was

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High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

Cited by 90 publications

References 84 publications

Interlayer excitons in a bulk van der Waals semiconductor

Interlayer excitons in a bulk van der Waals semiconductor

Superfluidity of dipolar excitons in a transition metal dichalcogenide double layer

Strong enhancement of third-harmonic generation in a double layer graphene system caused by electron-hole pairing

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