Leaky exciton condensates in transition metal dichalcogenide moiré bilayers

Remez, Benjamin; Cooper, Nigel R.

doi:10.48550/arxiv.2110.07628

Cited by 4 publications

(4 citation statements)

References 82 publications

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“…The moiré periodicity and the Coulomb repulsion can lead to the localization of an exciton in each moiré unit cell. Such an effect on the exciton condensate can be described by the moiré Bose-Hubbard (BH) Hamiltonian [54,55],…”

Section: (B)) ε Ementioning

confidence: 99%

Quantum anomalous Hall effect and electric-field-induced topological phase transition in AB-stacked MoTe${}_2$/WSe${}_2$ moiré heterobilayers

Chang¹,

Chang²

2022

Preprint

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We propose a new mechanism to explain the unexpected quantum anomalous Hall (QAH) effect and the electric-field-induced Mott-to-QAH phase transition without charge gap closure in ABstacked MoTe2/WSe2 moiré heterobilayers. We suggest that a hole-occupied band carrying a nonzero Chern number can be generated by an intrinsic band inversion between two topologically distinct Dirac bands and a Coulomb-interaction-induced gap opening in the moiré band structure with broken time-reversal symmetry (TRS). The Dirac-band dispersion is induced by a pseudomagnetic field, which is originated from the Berry phase of Bloch electrons in the presence of a moiré potential. The TRS is broken by valley-polarized interlayer-exciton condensation under an out-ofplane electric field. The valley polarization can be demonstrated by using an excitonic Bose-Hubbard (BH) model and Berezinskii-Kosterlitz-Thouless (BKT) transition to transverse ferromagnetism. In low electric fields, the equilibrium state of the system is a Mott insulator state. At a certain electric field, the exciton condensate combining with the Chern band becomes a more stable state and the Mott-to-QAH transition occurs. Since the band inversion is intrinsic, there is no charge gap closure at the transition.

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Section: (B)) ε Ementioning

confidence: 99%

Quantum anomalous Hall effect and electric-field-induced topological phase transition in AB-stacked MoTe${}_2$/WSe${}_2$ moiré heterobilayers

Chang¹,

Chang²

2022

Preprint

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“…Now the exciton condensation is still a hot topic, and various varieties, including pure optically active excitons, Moiré exciton, and trion-polaritons, have been investigated. [142][143][144] Additionally, the condensation of excitons into an electronhole liquid (EHL) has also been extensively investigated. [145] At low densities, excitons are noninteracting and behave like an ideal gas, which are hence referred to as "free excitons."…”

Section: Exciton Phase Transitionmentioning

confidence: 99%

Molding 2D Exciton Flux toward Room Temperature Excitonic Devices

Dai

Luo

et al. 2022

Adv Materials Technologies

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optoelectronic elements and devices. Owing to the unique talents of electrons and photons, the efficient photonic communication and electronic processing of signals have been proved as the essential and core components the information technology. Electrons as charged particles are sensitive to surroundings because of strong Coulomb interaction, leading to the bottleneck of nanosecond response time for integrated electric devices. The electronic response time and the conversation between photonic and electronic systems inevitably limit the operation speed in the conventional optoelectronic. [1] Thus developing compact photonic devices performing the essential logic operations is promising to accelerate information transmission and processing. In this direction, some simple prototypes, including optoelectronic transistor, compact microring resonator-based modulator, and Mach-Zehnder modulator, have been demonstrated. [2][3][4] The high integration of photonic devices is challenging due to the optical diffraction limit. Although the latter devices have achieved switching speeds exceeding several gigahertz, high packing density is greatly limited by their active-region dimensions of 10-100 µm. Excitons, or bound electron−hole pairs, Devices operating with excitons have promising prospects for overcoming the dilemma of response time and integration in current generation of electron-or/and photon-based elements and devices. In combination with the advantages of emerging twistronics and valleytronics, the atomically thin transition metal dichalcogenide semiconductors open up new opportunities for pursuing practical excitonic devices, where the strong exciton binding energy enables operating exciton at room temperature. The essential and foremost step toward exciton devices is the control of spatiotemporal exciton flux, which is density-dependent and affected by the complex many-body interactions. It can be effectively controlled by the strain, electric field, electron-doping, and local dielectric environment. Intriguingly, exotic phenomena such as exciton condensation, electron-hole liquid, exciton Hall effects, and exciton halo effects can be occurred in 2D exciton system, providing new possibilities for excitonic devices. Up to now, the proof-of-principle of room temperature exciton devices, including excitonic switching and transistor, exciton guides, and excitonic nanolaser, have been realized. Here the authors review the recent advances in molding 2D exciton flux from basic principle, manipulation, exotic phenomena to promising applications and discuss the opportunities and challenges in pushing the frontiers of room temperature excitonic devices.

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“…It is demonstrated that the MPDs lead to non-uniform dielectric properties in moiré superlattices, such as interlayer charge transfer, polarizability, and the evolution of the local band gap due to an applied field. Although the concept of a local band gap is in general ill-defined, it has been used to estimate the potential landscape for interlayer moiré excitons [17][18][19][20][21][22], giving rise to novel exciton dynamical, optical and many-body phenomena [23]. While the theory of lattice relaxation and its influence on structural properties of moiré superlattices is well-known [24,25], the practical details required to perform efficient calculations are typically omitted.…”

Section: Introductionmentioning

confidence: 99%

Theory of polar domains in moiré heterostructures

Bennett

2022

Preprint

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Leaky exciton condensates in transition metal dichalcogenide moiré bilayers

Cited by 4 publications

References 82 publications

Quantum anomalous Hall effect and electric-field-induced topological phase transition in AB-stacked MoTe${}_2$/WSe${}_2$ moiré heterobilayers

Quantum anomalous Hall effect and electric-field-induced topological phase transition in AB-stacked MoTe${}_2$/WSe${}_2$ moiré heterobilayers

Molding 2D Exciton Flux toward Room Temperature Excitonic Devices

Theory of polar domains in moiré heterostructures

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