Correlation-induced single-flux-quantum penetration in quantum rings

Abstract

Conventionally, the states of a two-dimensional quantum ring in a high magnetic field have a well-defined spatial structure. But Coulomb repulsion between individual orbits causes oscillations in the size of this structure each time a magnetic flux-quantum enters or leaves the system. This effect has now been measured experimentally in semiconducting quantum rings. The confined electronic states of mesoscopic structures in a magnetic field are arranged in Landau levels consisting of spatially discrete eigenstates. These Landau orbits are the quantum mechanical analogue of classical cyclotron orbits. Here we present magnetoconductance oscillations in semiconductor rings, which visualize the spatial discreteness of the Landau orbits in high magnetic fields (typically B>2 T). We will show that these oscillations are caused by the flux-quantized, discrete electronic size of the ring leading to a corresponding modulation of its two-point conductance. The oscillation period is given by the number of flux quanta penetrating the conducting area of the structure. These high-field oscillations are distinctively different from the well-known Aharonov–Bohm effect1, where, most generally, the penetration of individual flux quanta h/e through a nanostructure causes periodic crossings of field-dependent energy levels, which give rise to magneto-quantum oscillations in its conductance2,3,4.