High-Quality Single-Crystal PdCoO₂ Nanomembranes Prepared by Mechanical Exfoliation for Mesoscopic Transport Studies

Certain delafossite oxides have recently attracted significant attention owing to their remarkable transport properties, including extremely low resistivity at low temperatures and highly coherent electron transport. However, the study of their mesoscopic transport is hindered by the difficulty of fabricating high-quality nanoscale samples. Here, we report the preparation of single-crystalline PdCoO₂ nanomembranes via mechanical exfoliation. Due to the quasi-two-dimensional crystal structure, nanomembranes down to 15 nm thickness can be achieved using this technique, allowing exploration of electronic transport in the near-2D limit. The nanomembranes exhibit a large breakdown current density as high as 113 MA cm⁻² at room temperature. Angle-resolved magneto-transport measurements performed at 300 mK under high magnetic fields reveal clear Aharonov–Bohm and Shubnikov–de Haas oscillations at different field orientations. The extracted electron phase-coherence length reaches approximately 10 µm. These results show that the mechanically exfoliated PdCoO₂ flakes preserve the high crystalline quality of bulk crystals, providing a highly convenient approach for preparing high-quality thin samples for mesoscopic transport studies.