Valley Phenomena in the Candidate Phase Change Material WSe${}_{2(1-x)}$Te${}_{2x}$

Abstract

Alloyed transition metal dichalcogenides provide an opportunity for coupling band engineering with valleytronic phenomena in an atomically-thin platform. However, valley properties in alloys remain largely unexplored. We investigate the valley degree of freedom in monolayer alloys of the phase change candidate material WSe${}_{2(1-x)}$Te${}_{2x}$. Low temperature Raman measurements track the alloy-induced transition from the semiconducting 1H phase of WSe${}_2$ to the semimetallic 1T${}_d$ phase of WTe${}_2$. We correlate these observations with density functional theory calculations and identify new Raman modes from W-Te vibrations in the 1H alloy phase. Photoluminescence measurements show ultra-low energy emission features that highlight alloy disorder arising from the large W-Te bond lengths. Interestingly, valley polarization and coherence in alloys survive at high Te compositions and are more robust against temperature than in WSe${}_2$. These findings illustrate the persistence of valley properties in alloys with highly dissimilar parent compounds and suggest band engineering can be utilized for valleytronic devices.

arXiv commentManuscript: 27 pages, 6 figures, 1 table. Supplementary Information: 15 pages, 12 figures, 2 notes

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Cited by in corpus (1)

• Inducing room-temperature valley polarization of excitonic emission in transition metal dichalcogenide monolayers