Enhanced electron coherence in atomically thin Nb3SiTe6.

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 MoS₂ 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 Nb₃SiTe₆ atomic crystals. When the thickness of the Nb₃SiTe₆ 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. [ABSTRACT FROM AUTHOR]