Reciprocal and non-reciprocal energy and momentum drag between 1D and 2D conductors

Double-layer drag experiments are an exceptionally sensitive tool for studying interactions in low-dimensional systems, since the drag response depends on long-range Coulomb interactions rather than particle exchange. Graphene in particular has exhibited unusual drag effects near charge neutrality that have been attributed to competing energy and momentum transfer between the layers. We have performed measurements of 1D-2D drag resistance between a single carbon nanotube (CNT) and monolayer graphene separated by a few-layer boron nitride flake. At high temperatures, the drag response is symmetric under interchange of the drive and drag layers, and resembles momentum transfer from drive to drag layer. This layer reciprocity is broken near the charge neutrality point of graphene at lower temperatures, which can be attributed to energy transfer or thermoelectric effects. Intriguingly, the high-temperature drag response decays with distance from the CNT slower than expected from the Ohmic diffusive current distribution. This suggests additional electron interactions coming into play near charge neutrality in the graphene layer.