Odd-even conductance oscillations in meta-cycloparaphenylenes

Molecular-scale electronics seeks to transcend classical device paradigms by leveraging the quantum nature of charge transport. Molecular orbitals, as electron wave functions, exhibit spatially structured amplitude and nodal patterns that shape electron transmission. Yet, the spatial characteristics are difficult to resolve experimentally in single-molecule junctions. Here, we report the direct observation of length-dependent odd-even conductance oscillations that arise from sampling different regions of a single π-orbital at room temperature. This is enabled by anchor-free single-molecule junctions, where cyclic carbon nanohoop molecules form Au-π contacts with gold electrodes, allowing the intrinsic π-orbital profile to be probed directly. This minimal-contact design preserves orbital symmetry and reveals conductance variations linked to the orbital's spatial amplitude distribution, as corroborated by first-principles transport calculations. These results demonstrate that the spatial structure of an individual molecular orbital can measurably influence room-temperature charge transport, providing a clear framework for understanding orbital contributions in molecular-scale electronic systems.