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Magnetic Field Driven Coherent Coupling of Bright and Dark Excitons

Published April 24, 2023

Experimental setup using the 25T Split-Helix magnet and the multidimensional optical nonlinear spectrometer (MONSTR).
Experimental setup using the 25T Split-Helix magnet and the multidimensional optical nonlinear spectrometer (MONSTR).

Probing one of the prominent classes of atomically-thin materials, the transition metal dichalcogenides, researchers found that while dark excitons are not optically responsive, they do interact with bright excitons and as a result, affect the lifetime and coherence of the bright excitons. Understanding the interaction between dark and bright excitons is critical to the future use of these materials in quantum information technologies.

What did scientists discover?

Electron-hole pairs (excitons) in semiconducting materials are referred to as bright or dark based on their response to optical stimulation. Properties of two-dimensional (2D) materials that cannot be directly seen – properties called “dark” – can still affect important optical behaviors of a two-dimensional material. Large magnetic fields can manipulate these unseen “dark” properties by coupling them to visible – or “bright” – properties.

The experiment explored one of the prominent classes of atomically-thin, two-dimensional materials, the transition metal dichalcogenides, and found that magnetic-field-driven coupling enabled the dark quasi-particles to interact with the bright optical properties, thereby changing the optical properties of the 2D material.  

Why is this important?

Many two-dimensional materials grow naturally in atomically thin layers. Their applications range from light emitting devices and displays, to electronic devices, to solar cells. Understanding their optical properties under extreme conditions is important for understanding their behavior when directed toward potential applications. In particular, understanding how the “dark” properties affect the desired optical emission and coherence of the “bright” properties is crucial for optimizing materials considerations when designing devices for new applications like the future use of these materials in quantum information technologies.

Who did the research?

Varun Mapara1, Arup Barua1, Volodymyr Turkowski2, M. Tuan Trinh1, Christopher Stevens1, Hengzhou Liu1, Florence A. Nugera1, Nalaka Kapuruge1, Humberto Rodriguez Gutierrez1, Fang Liu3, Xiaoyang Zhu4, Dmitry Semenov5, Stephen A. McGill5, Nihar Pradhan6, David J. Hilton7, and Denis Karaiskaj1

1University of South Florida; 2University of Central Florida; 3Stanford University; 4Columbia University; 5National MagLab; 6Jackson State University; 7University of Alabama

Why did they need the MagLab?

As with virtually all materials from which one seeks to develop a new solid-state device, very high magnetic fields are necessary to manipulate the coherence of wave-functions and/or the coupling of energy levels in order to provide a fundamental understanding of the material and, hence, the potential to manipulate the material toward new applications.  The MagLab’s 25T Split-Helix magnet is a world-unique magnet, enabling direct optical access to the sample as it sits at the center of the 25T magnetic field.

Details for scientists


This research was funded by the following grants: Denis Karaiskaj (DOE DE-SC0012635); Xiaoyang Zhu (NSF DMR-2011738); Volodymyr Turkowski (DOE DE-FG02-07ER46354); G.S. Boebinger (NSF DMR-1644779)

For more information, contact Tim Murphy.

Last modified on 24 April 2023