Researchers have successfully combined two types of electron-hole pairs

اقتران أزواج ثقب الإلكترون

Color map of the calculated absorption Im (χ) as a function of the electric field Fz. attributed to him: physical review messages (2022). DOI: 10.1103/ PhysRevLett.129.107401

2D Van der Waals materials have been the focus of the work of many research groups for some time. Standing just a few atomic layers thick, these structures are produced in a laboratory by combining atom-thick layers of different materials (in a process referred to as “atomic lego”). Interactions between stacked layers allow heterogeneous structures to show properties that the individual components lack.

Bilayer molybdenum disulfide is one of the van der Waals materials, in which electrons can be excited using a suitable experimental setup. Then these negatively charged particles leave their position in equivalence range, leaving a positively charged hole behind, and enter the conduction band. Given the different charges of the electrons and holes, the two are attracted to each other and form what is known as a quasiparticle. The latter is also referred to as the electron-hole pair, or exciton, and can move freely within the material.

In bilayer molybdenum disulfide, photoexcitation results in two different types of electron-hole pairs: interlayer pairs, in which the electron and hole are localized in the same material layer, and interlayer pairs, in which the hole and electron are located in different layers and are therefore spatially separated from each other .

These two types of electron-hole pairs have different properties: the inner layer pairs interact strongly with light—in other words, they glow intensely. On the other hand, interfacial excitons are darker but can be converted to different energies, thus allowing researchers to tune the absorbed wavelength. In contrast to intralayer excitons, interfacial excitons also show very strong nonlinear interactions with each other—and these interactions play an essential role in many of their potential applications.

merging properties

Now, researchers from the group led by Professor Richard Warburton of the Department of Physics and the Swiss Institute for Nanoscience (SNI) at the University of Basel have correlated these two types of electron-hole pairs by bringing the two to similar energies. This convergence is only possible thanks to the tunability of the interlayer excitons, and the resulting coupling merges the properties of the two types of electron-hole pair. So researchers can design compact particles that are not only extremely bright but also interact strongly with each other.

“This allows us to combine the beneficial properties of both types of electron-hole pairs,” explains Lukas Sponfeldner, a doctoral student at SNI Ph.D. School and first author of the paper. “These combined properties can be used to produce a new source of single photons, which are an essential component of quantum communication.”

Compatible with classic models

In the paper published in physical review messagesthe researchers also showed that this complex system of electron-hole pairs can be simulated using classical models from the fields of mechanics or electronics.

especially, Electron-hole pairs They can effectively be described as oscillating blocks or circuits. “These simple and general comparisons help us gain a better understanding of the fundamental properties of paired particles, not only in molybdenum disulfide but also in many other physical systems and contexts,” explains Professor Richard Warburton.

Highly absorbent and adjustable material

more information:
Lukas Sponfeldner et al, Capacitance and inductive coupled excitons in the MoS . bilayer2And the physical review messages (2022). DOI: 10.1103/ PhysRevLett.129.107401

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