Related Experiment Video
Updated: Oct 12, 2025
09:00
Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
Published on: June 28, 2018
10.1K
Valley-exchange coupling probed by angle-resolved photoluminescence
Joshua J P Thompson1, Samuel Brem2, Hanlin Fang3
1Department of Physics, Chalmers University of Technology, Gothenburg 412 96, Sweden. thompson@chalmers.se.
Nanoscale Horizons
|November 19, 2021
Summary
Angle-resolved photoluminescence can probe excitonic dispersion changes in transition metal dichalcogenides. Magnetic fields tune these optical properties, verifying valley-exchange coupling effects.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Optics
Background:
- Monolayer transition metal dichalcogenides exhibit unique optical properties dominated by strongly-bound excitons.
- These excitons form at specific points (valleys) in reciprocal space and interact through valley-exchange coupling, significantly altering their energy-momentum relationship (dispersion).
Purpose of the Study:
- To predict and demonstrate how angle-resolved photoluminescence can be utilized to investigate modifications in excitonic dispersion.
- To explore the influence of valley-exchange coupling on the angle-dependent optical emission characteristics.
Main Methods:
- Theoretical prediction of angle-resolved photoluminescence spectra.
- Analysis of the angle dependence of emission intensity for circularly and linearly polarized light.
- Investigation of the effects of external magnetic fields on these optical signatures.
Main Results:
- Valley-exchange coupling introduces a distinct angle dependence in the photoluminescence intensity for both circular and linear polarizations.
- External magnetic fields, via the valley-specific Zeeman effect, can significantly tune these angle-dependent emission characteristics.
- The study predicts unique optical signatures arising from valley-exchange coupling.
Conclusions:
- Angle-resolved photoluminescence is a viable technique for probing excitonic dispersion changes in transition metal dichalcogenides.
- The interplay of optical polarization, angle dependence, and magnetic fields provides strong evidence for the role of valley-exchange coupling.
- This approach can verify the impact of valley-exchange coupling on excitonic behavior and its optical manifestations.
Related Concept Videos
01:14Photoluminescence: Applications
545
Photoluminescence offers a wide range of applications due to its inherent sensitivity and selectivity. This technique allows for both direct and indirect analyses of the analyte. Direct quantitative analysis is possible when the analyte exhibits a favorable quantum yield for fluorescence or phosphorescence. However, an indirect analysis may be feasible if the analyte is not fluorescent or phosphorescent, or if the quantum yield is unfavorable. Indirect methods include reacting the analyte with...
545
01:23Photoluminescence: Fluorescence and Phosphorescence
2.5K
Photoluminescence is a process where a molecule absorbs light energy and re-emits it in the form of light. This phenomenon occurs when a substance absorbs photons, promoting its electrons to higher energy level excited states, followed by a relaxation process in which the electrons return to their original ground state energy levels and emit light. Photoluminescence is widely observed in various materials, including semiconductors, and organic and inorganic compounds.
A pair of electrons in a...
A pair of electrons in a...
2.5K
01:25Fluorescence and Phosphorescence: Instrumentation
899
Fluorometers and spectrofluorometers are two types of instruments used for measuring molecular fluorescence. These instruments differ in how they select excitation and emission wavelengths and the type of light sources they utilize. Fluorometers use absorption interference filters to choose excitation and emission wavelengths. The excitation source in a fluorometer is typically a low-pressure mercury vapor lamp that emits intense lines distributed throughout the ultraviolet and visible regions.
899
01:29Atomic Fluorescence Spectroscopy
547
Atomic fluorescence spectroscopy (AFS) is an analytical technique that involves the electronic transitions of atoms in a flame, furnace, or plasma being excited by electromagnetic (EM) radiation. When these atoms absorb energy, they become excited and subsequently release energy as they return to their original state. This emitted light, or "fluorescence," is observed at a right angle to the incident beam. Both absorption and emission processes transpire at distinct wavelengths, which...
547
01:23Atomic Spectroscopy: Absorption, Emission, and Fluorescence
1.6K
Atomic spectroscopy is a vital tool in elemental analysis, both qualitatively and quantitatively. It can be broadly divided into optical spectroscopy, mass spectroscopy, and X-ray spectroscopy methods. The optical spectroscopic methods are atomic absorption spectroscopy (AAS), atomic emission spectroscopy (AES), and atomic fluorescence spectroscopy (AFS). The first step in all three methods is atomization, where the solid, liquid, or solution-phase samples are converted into gas-phase atoms and...
1.6K
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
2.0K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
2.0K