Anisotropic superfluidity of two-dimensional excitons in a periodic potential

Lozovik, Yu. E.; Kurbakov, I. L.; Volkov, Pavel A.

doi:10.1103/physrevb.95.245430

Cited by 8 publications

(3 citation statements)

References 201 publications

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“…In case of dipolar BECs, however, transport measurements reveal the anisotropy of the critical Landau velocity rather than the velocity of sound 33 , since the dispersion of excitations is affected by direction-dependent roton softening. The situation realized in our work can be better compared with anisotropic superfluidity reported for excitons 34 and cavity photon BEC 35 in periodically modulated planar structures. At the same time, we stress that here we deal with a more exotic case of anisotropy: even though there is a well-defined finite sound velocity, superfluidity in the sense of Landau criterion cannot be reached in all directions of propagation.…”

Section: Discussionsupporting

confidence: 54%

Collective excitations of a bound-in-the-continuum condensate

et al. 2023

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Spectra of low-lying elementary excitations are critical to characterize properties of bosonic quantum fluids. Usually these spectra are difficult to observe, due to low occupation of non-condensate states compared to the ground state. Recently, low-threshold Bose-Einstein condensation was realised in a symmetry-protected bound state in the continuum, at a saddle point, thanks to coupling of this electromagnetic resonance to semiconductor excitons. While it has opened the door to long-living polariton condensates, their intrinsic collective properties are still unexplored. Here we unveil the peculiar features of the Bogoliubov spectrum of excitations in this system. Thanks to the dark nature of the bound-in-the-continuum state, collective excitations lying directly above the condensate become observable in enhanced detail. We reveal interesting aspects, such as energy-flat parts of the dispersion characterized by two parallel stripes in photoluminescence pattern, pronounced linearization at non-zero momenta in one of the directions, and a strongly anisotropic velocity of sound.

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Section: Discussionsupporting

confidence: 54%

Collective excitations of a bound-in-the-continuum condensate

et al. 2023

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“…We consider excitons as bosons since the overlap integral of exciton wavefunctions is exponentially small (see Ref. [55]). We also note that chemical potentials µ b(d) may not be equal to each other since we assume no interlayer hopping.…”

Section: Bilayer Dark-bright Condensate Systemmentioning

confidence: 99%

Optical probing in a bilayer dark-bright condensate system

et al. 2019

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We consider a bilayer system of two-dimensional Bose-Einstein-condensed dipolar dark excitons (upper layer) and bright ones (bottom layer). We demonstrate that the interlayer interaction leads to a mixing between excitations from different layers. This mixing leads to the appearance of a second spectral branch in the spectrum of bright condensate. The excitation spectrum of the condensate of dark dipolar excitons then becomes optically accessible during luminescence spectra measurements of the bright condensate, which allows one to probe its kinetic properties. This approach is relevant for experimental setups, where detection via conventional techniques remains challenging, in particular, the suggested method is useful for studying dark dipolar excitons in transition metal dichalcogenide monolayers.

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“…There are many unexplored problems in the interlayer coupling of TMDs/h-BN heterostructures, and it is necessary to have a better understanding and application of vdW heterostructure [ 13 , 14 ]. The heterostructure combination of any layered materials can be prepared by transfer method, so the devices with new functions and characteristics are also realized by combining the different characteristics materials [ 15 , 16 ]. For the mass production of heterostructure materials, the mechanical peeling stack method is not suitable, due to the lower yield [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of MoS2/h-BN and WS2/h-BN Heterostructures

et al. 2020

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The general preparation method of large-area, continuous, uniform, and controllable vdW heterostructure materials is provided in this paper. To obtain the preparation of MoS2/h-BN and WS2/h-BN heterostructures, MoS2 and WS2 material are directly grown on the insulating h-BN substrate by atmospheric pressure chemical vapor deposition (APCVD) method, which does not require any intermediate transfer steps. The test characterization of MoS2/h-BN and WS2/h-BN vdW heterostructure materials can be accomplished by optical microscope, AFM, Raman and PL spectroscopy. The Raman peak signal of h-BN material is stronger when the h-BN film is thicker. Compared to the spectrum of MoS2 or WS2 material on SiO2/Si substrate, the Raman and PL spectrum peak positions of MoS2/h-BN heterostructure are blue-shifted, which is due to the presence of local strain, charged impurities and the vdW heterostructure interaction. Additionally, the PL spectrum of WS2 material shows the strong emission peak at 1.96 eV, while the full width half maximum (FWHM) is only 56 meV. The sharp emission peak indicates that WS2/h-BN heterostructure material has the high crystallinity and clean interface. In addition, the peak position and shape of IPM mode characteristic peak are not obvious, which can be explained by the Van der Waals interaction of WS2/h-BN heterostructure. From the above experimental results, the preparation method of heterostructure material is efficient and scalable, which can provide the important support for the subsequent application of TMDs/h-BN heterostructure in nanoelectronics and optoelectronics.

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Anisotropic superfluidity of two-dimensional excitons in a periodic potential

Cited by 8 publications

References 201 publications

Collective excitations of a bound-in-the-continuum condensate

Collective excitations of a bound-in-the-continuum condensate

Optical probing in a bilayer dark-bright condensate system

Fabrication and Characterization of MoS2/h-BN and WS2/h-BN Heterostructures

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