Coherent electron transmission across twin boundaries in Cu(111).

Copper thin films are foundational to modern electronics and nanotechnology, yet their charge transport is limited fundamentally by electron scattering at atomic-scale imperfections. Recent advances in atomic sputtering epitaxy (ASE) have enabled the growth of grain-boundary-free Cu(111) films, but defects such as twin boundaries and atomic step edges persist as intrinsic scattering centers. Here, we report that scanning tunneling spectroscopy measurements on Cu(111) films reveal pronounced quantum interference, indicating non-dephasing, elastic scattering across these atomically sharp discontinuities. The structural symmetry of the discontinuities, combined with identical Fermi surface on either side of the interface, facilitates unexpectedly high transmission probabilities and preserve phase coherence - fundamentally distinguishing ASE grown single crystalline thin films from the diffusive transport characteristic found in polycrystalline copper. These findings reveal that despite the presence of atomic discontinuities, Cu(111) can support highly transparent, coherent electron flow without invoking topological protection. These findings establish a framework of utilizing conventional metals in coherent, low-dissipation nanoscale electronic devices.