Interlayer Exciton–Phonon Bound State in Bi₂Se₃/Monolayer WS₂ van der Waals Heterostructures

Abstract

The ability to assemble layers of two-dimensional (2D) materials to form permutations of van der Waals heterostructures provides significant opportunities in materials design and synthesis. Interlayer interactions can enable desired properties and functionality, and understanding such interactions is essential to that end. Here we report formation of interlayer exciton–phonon bound states in Bi2Se3/WS2 heterostructures, where the Bi2Se3 A1 (3) surface phonon, a mode particularly susceptible to electron–phonon coupling, is imprinted onto the excitonic emission of the WS2. The exciton–phonon bound state (or exciton–phonon quasiparticle) presents itself as evenly separated peaks superposed on the WS2 excitonic photoluminescence spectrum, whose periodic spacing corresponds to the A1 (3) surface phonon energy. Low-temperature polarized Raman spectroscopy of Bi2Se3 reveals intense surface phonons and local symmetry breaking that allows the A1 (3) surface phonon to manifest in otherwise forbidden scattering geometries. Our work advances knowledge of the complex interlayer van der Waals interactions and facilitates technologies that combine the distinctive transport and optical properties from separate materials into one device for possible spintronics, valleytronics, and quantum computing applications.

Supersensitive and Broadband Photodetectors Based on High Concentration of Er3+/Yb3+ Co‐doped WS2 Monolayer

“…Both of the samples show nearly 1 nm of thicknesses, which is regularly assigned to monolayer. [32][33][34] Raman spectrum is an effective way to analyze the structure of 2D materials through vibration and rotation of molecules. As shown in Figure 3e, the Raman spectra of the monolayer WS 2 and WS 2 (Er/Yb) are demonstrated by using a 532 nm excitation laser.…”

Quantum Phase Transitions of Interlayer Excitons in van der Waals Heterostructures

“…Both of them display the discrepancies of the lattice relaxation effect between LST and HST, which also could be evaluated quantificationally by the well-known Huang-Rhys factors given in Table S2, Supporting Information. In fact, self-trapped exciton states arising from the strong coupling between the excitons and phonons lead to a number of phonon replicas, which have been observed in many optical experiments, such as the LO phonon replicas of free excitons and neutral donor-bound excitons, [50][51][52] as well as MRS. [53][54][55][56][57][58] In particular, the strength of excitonphonon coupling, the lattice distortion, and the change in vibrational modes can be directly evaluated by MRS. However, what puzzle is that MRS can also be induced by FS in many past experiments.…”

Electric Control of Helicity-Dependent Photocurrent and Surface Polarity Detection on Two-Dimensional Bi2O2Se Nanosheets

“…Controlling and manipulating electron spins in nonmagnetic semiconductor materials with a strong spin orbit interaction (SOI) have received intense interest in the field of spintronics. − Bismuth oxyselenide (Bi 2 O 2 Se) is a two-dimensional (2D) layered semiconductor material with high electron Hall mobility and good environmental stability, which exhibits excellent electron transport and optical properties for photoelectric applications. − Recently, the existence of strong SOI has been experimentally demonstrated in Bi 2 O 2 Se nanosheets, which inaugurates the possibility of Bi 2 O 2 Se for application in spintronics and quantum devices. , Previous research has established that Bi 2 O 2 Se is composed of Bi–O 2 –Bi trilayers with positively charged and Se atomic layers with a compensating negative charge, which may lead to the metallic Rashba-split surface states on the polar surfaces. − These surface states stem from huge potential bending, positive or negative, depending on surface polarity, and reside partially in the bulk band gap, leaving appropriate space for multifunctional electrical tuning. , However, so far, there is no method that can differentiate between the Bi- or Se-terminated surfaces. Since the lattice polarity is a very important issue for the study of Bi 2 O 2 Se, which will lead to different surface electronic structures, it is necessary to carry out systematic investigations to distinguish the lattice polarity of Bi 2 O 2 Se.…”