Search

Moiré superlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials. The periodic moiré patterns generated by these structures lead to the formation of flat mini-bands, which alter the electronic energy bands of the material. The resulting flat electronic bands can greatly enhance strong correlative interactions between electrons, leading to the emergence of exotic quantum phenomena, including moiré phonons and moiré excitons. While extensive research has been conducted on the exotic quantum phenomena in twisted bilayers of transition metal dichalcogenides (TMDs), and the regulatory effect of stacked layers on moiré excitons remains unexplored. In this study, we report the fabrication of a twisted WSe2/WSe2/WSe2 homotrilayer with two twist angles and investigate the influence of stacked layers on moiré excitons. Our experiments reveal multiple moiré exciton splitting peaks in the twisted trilayer, with moiré potential depths of 78 and 112 meV in the bilayer and trilayer homostructures, respectively. We also observed the splitting of the moiré excitons at 90 K, indicating the presence of a deeper moiré potential in the twisted trilayer. Moreover, we demonstrate that stacked layers can tune the moiré excitons by manipulating temperature, laser power, and magnetic field. Our results provide a new physical model for studying moiré superlattices and their quantum properties, which could potentially pave the way for the development of quantum optoelectronics. [ABSTRACT FROM AUTHOR]

The excitonic effects in two-dimensional transition metal dichalcogenides and their heterostructures have been extensively investigated. Significantly, the moiré excitons, induced by a moiré superlattice in a twisted heterostructure, have triggered tremendous attention, demonstrating the practicability of artificial excitonic crystals. Besides, recent works have shown that the excitonic states in homostructures also exhibit novel properties worthy of further development. Here, we present a tear-and-stack technique for fabricating a regular or a twisted homostructure. Such a strategy was utilized to reassemble a monolayer WSe2 into a twisted homostructure, and various excitons from this structure have been identified in the photoluminescence spectra. Interestingly, the unusual equidistant splitting was first observed in the defect-bound excitons. It is believed that this phenomenon is attributed to the various defect states and the local stacking patterns. This interpretation is supported by theoretical calculations, which show the dependence of the energy band structure on different defect states and local stacking patterns. These unconventional defect-bound excitons are key building blocks in the research of homostructures that highlight the feasibility of artificially manipulating local excitons for practical applications. [ABSTRACT FROM AUTHOR]

Photoelectronic properties can be effectively modulated by external mechanical stimulation, which have been widely researched on materials with non-centrosymmetric wurtzite structure. Topological insulator (TI) materials with symmetric crystal structure have been theoretically predicted that its photoelectronic properties would also be greatly modulated through strain modulation effect. Here, for the first time, we experimentally demonstrate the strain modulation effect of TI Bi 2 Se 3 nanowires (NWs), opening an innovative way to enhance the optoelectronic performance of TI materials. Single-crystal TI Bi 2 Se 3 NWs were synthesized via a micro-environmental control chemical vapor deposition method. Based on these NWs, a high-performance photodetector (PD) with high responsivity, and broadband detection range from ultraviolet to near-infrared were fabricated. By introducing an external 0.54% compressive strain, the photocurrent and responsivity were enhanced by 97% and 503%, respectively, upon excitation by 442 nm light with an intensity of 17.6 mW/cm2. A theoretical model of the schematic energy band diagram was proposed to illustrate the enhancement mechanism. The results of theoretical calculation indicate that the conduction band of the TI can be modulated by strain, which can then influence the metal-semiconductor (M-S) junction potential for charges transport. This study reports a high-quality TI Bi 2 Se 3 NWs based strain-modulated PDs, broadening the family of strain modulation materials system, and offering a promising material for high-performance broadband detectors. • High quality of topological insulator Bi2Se3 NWs were synthesized with micro-environment controlled CVD process. • High performance of broad spectrum detection range from ultraviolet to infrared were demonstrated. • The strain modulation effect of topological insulator Bi2Se3 NWs was firstly demonstrated experimentally. [ABSTRACT FROM AUTHOR]