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Valley phenomena in the candidate phase change material WSe2(1-x)Te2x
Sean M Oliver1,2, Joshua Young3, Sergiy Krylyuk4,5
1Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA.
Communications Physics
|November 23, 2020
Summary
Valley properties in transition metal dichalcogenide alloys are explored. These alloys maintain valley coherence even at high tellurium compositions, suggesting potential for advanced valleytronic devices.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Alloyed transition metal dichalcogenides offer a platform for combining band engineering and valleytronics.
- Valley properties in these alloys are not well understood.
Purpose of the Study:
- Investigate valley degree of freedom in monolayer tungsten diselenide-ditelluride (WSe2(1-x)Te2x) alloys.
- Explore the impact of alloying on phase transitions and electronic properties.
Main Methods:
- Low-temperature Raman spectroscopy to monitor phase transitions.
- Density functional theory (DFT) calculations for theoretical correlation.
- Photoluminescence (PL) spectroscopy to analyze electronic emission features.
Main Results:
- Observed alloy-induced transition from semiconducting 1H phase (WSe2) to semimetallic 1Td phase (WTe2).
- Identified new Raman modes associated with W-Te vibrations in the 1H-phase alloy.
- Detected ultra-low energy emission features in PL, indicating alloy disorder.
- Demonstrated that valley polarization and coherence persist at high Te concentrations and are temperature-robust.
Conclusions:
- Valley properties are surprisingly robust in alloys of dissimilar parent compounds.
- Band engineering in these alloys can be leveraged for developing novel valleytronic devices.
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