Warming up Valley Polarization

November 16, 2023

Illustration showing photo-excited spin- down electrons from one MoS₂ energy valley being selectively transferred to the chiral perovskite. Spin- up electrons in the second MoS₂ valley recombine radiatively, emitting polarized light.

Scientific Achievement

CFN staff led a collaborative team that realized room-temperature, selective population of a specific energy valley (valley polarization) in a 2D quantum material (MoS₂), by coupling it to a chiral perovskite material for spin-selective charge transfer.

Significance and Impact

The degenerate energy valleys in quantum materials have potential for robustly storing/processing classical or quantum information. This work demonstrates a material heterostructure capable of maintaining valley polarization at room temperature, which is desirable for practical devices.

Research Details

2D transition metal dichalcogenides have two degenerate valleys and are promising quantum materials. Electrons in these materials can occupy either one of the two valleys and possess a valley degree of freedom. Therefore, in addition to electrons’ charge and spin, the valley they occupy can be used to carry information. By utilizing this additional degree of freedom, “valleytronics” could revolutionize the way we store and process information today, enabling more efficient and faster computing. Typically, cryogenic temperatures are required to maintain valley polarization due to higher intervalley scattering at higher temperatures. The low temperature requirements make these systems complex and expensive, limiting their practical application. Here, we demonstrate valley polarization at room temperature in MoS₂/chiral-perovskite heterostructures, which paves the way for practical valleytronics devices.

• MoS₂/chiral-perovskite heterostructures were fabricated using the CFN Quantum Materials Press
• Heterostructures were optically excited with linearly polarized light close to resonance, and the degree of polarization was obtained by measuring helicity resolved photoluminescence
• The CFN Advanced Optical Microscopy & Spectroscopy, Materials Synthesis & Characterization, and Proximal Probes Facilities were leveraged for this work

Publication Reference

Shrestha S.*, Li M., Park S., Tong X., DiMarzio D., Cotlet M.* “Room temperature valley polarization via spin selective charge transfer.” Nature Communications 14, 5234 (2023).

DOI: https://doi.org/10.1038/s41467-023-40967-7

OSTI: https://www.osti.gov/biblio/1996839

Brookhaven Newsroom: Valleytronics is Warming Up at Brookhaven Lab

Acknowledgment of Support

This research used facilities at the Center for Functional Nanomaterials (CFN), which is a U.S. Department of Energy Office of Science User Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. S.S., M.L., S.P., X.T., and M.C. are supported by U.S. Department of Energy Office of Science Grant DE-SC0012704. The authors thank Xuance Jiang from Stony Brook University

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