Electrodynamic dip in the local density of states of a metallic wire

We have measured the differential conductance of a tunnel junction between a thin metallic wire and a thick ground plane, as a function of the applied voltage. We find that near zero voltage, the differential conductance exhi bits a dip, which scales as 1/rootV down to voltages V similar to 10k(B)T/e . Th; precise voltage and temperature dependence of the differential conduc tance is accounted fur by the effect on the tunneling density of states of the macroscopic electrodynamics contribution to electron-electron interacti on, and not by the short-ranged screened-Coulomb repulsion at microscopic s cales.