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It is now well established that many of the technologically important properties of two-dimensional (2D) materials, such as the extremely high carrier mobility in graphene and the large direct band gaps in MoS 2 monolayers, arise from quantum confinement. However, the influence of reduced dimensions on electron-phonon (e-ph) coupling and its attendant dephasing effects in such systems has remained unclear. Although phonon confinement is expected to produce a suppression of e-ph interactions in 2D systems with rigid boundary conditions, experimental verification of this has remained elusive. Here, we show that the e-ph interaction is, indeed, modified by a phonon dimensionality crossover in layered Nb 3 SiTe 6 atomic crystals. When the thickness of the Nb 3 SiTe 6 crystals is reduced below a few unit cells, we observe an unexpected enhancement of the weak-antilocalization signature in magnetotransport. This finding strongly supports the theoretically predicted suppression of e-ph interactions caused by quantum confinement of phonons.

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Nature Physics

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