Fano interference in nanoscale bismuth constrictions

We report on electrical transport measurements of ballistic Bi constrictions with top and bottom gate electrodes in which interference of their metalliclike surface states and quantized bulk states results in Fano resonance features in the conductance. Within the formed constrictions, the mean spacing between the bulk states is smaller than their coupling to the leads. Under these conditions, gradual lapses in the scattering phases of the bulk states in response to a change in the gate voltage are inferred by analyzing the symmetry parameter of the Fano features. Comparison between the results of this analysis in response to the top and bottom gates also suggests that the surface states are localized at the interface between the Bi and the underlying SiO2 layer. Our findings advocate that nanofabrication of Bi could better harness its unique electronic properties to impart advanced functionalities.