Single-atom thermometer

Measuring temperature with nanoscale resolution has proven extraordinarily difficult because scanning probes lack the thermal isolation needed to achieve high spatial resolution. We propose a novel method to measure temperature with sub-nanometer resolution using individual physisorbed atoms as surface thermometers. We study the diffusive dynamics of aluminum adatoms adsorbed on graphene nanoflakes subject to a thermoelectric bias leading to a nontrivial spatial temperature distribution. The adatoms couple to local thermal fluctuations of both the vibrational and electronic degrees of freedom. The electronic coupling is mediated by Coulomb interactions, and is treated using the nonequilibrium Green's function method (NEGF). The adatom motion can be followed by STM in real time, and we find that they seek out the cold spots on the surface, thereby serving as thermometers.