Tunable Fano system: a quantum dot embedded in an Aharonov–Bohm ring

The Fano effect illustrates how the quantum interference occurs between a localized state and the energy continuum. While this phenomenon is ubiquitously observed in many different physical systems, it has been difficult to obtain a Fano system with desired parameters. We have realized for the first time a tunable Fano system by fabricating a quantum dot (QD) embedded in an Aharonov–Bohm interferometer on a two-dimensional electron gas. In the Coulomb oscillation, clear asymmetric lineshapes were observed, which manifest the formation of the Fano state, i.e., a mixture of the localized-continuum states. The Fano interference can be tuned through the phase of the electrons by the magnetic flux piercing the ring, revealing that Fanoʹs asymmetric parameter q should be complex.