title: Strong quantum scarring by local impurities.
abstract: We discover and characterise strong quantum scars, or quantum eigenstates resembling classical periodic orbits, in two-dimensional quantum wells perturbed by local impurities. These scars are not explained by ordinary scar theory, which would require the existence of short, moderately unstable periodic orbits in the perturbed system. Instead, they are supported by classical resonances in the unperturbed system and the resulting quantum near-degeneracy. Even in the case of a large number of randomly scattered impurities, the scars prefer distinct orientations that extremise the overlap with the impurities. We demonstrate that these preferred orientations can be used for highly efficient transport of quantum wave packets across the perturbed potential landscape. Assisted by the scars, wave-packet recurrences are significantly stronger than in the unperturbed system. Together with the controllability of the preferred orientations, this property may be very useful for quantum transport applications.
authors.affiliation: Nanoscience Center, Department of Physics, University of Jyväskylä, Jyväskylä FI-40014, Finland.|Department of Physics, Tampere University of Technology, Tampere FI-33101, Finland.
authors.forename: Perttu J J
authors.initials: PJ
authors.lastname: Luukko
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Byron
authors.initials: B
authors.lastname: Drury
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Klales
authors.affiliation: Department of Physics and Engineering Physics, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Lev
authors.initials: L
authors.lastname: Kaplan
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Heller
authors.affiliation: Department of Physics, Tampere University of Technology, Tampere FI-33101, Finland.
authors.forename: Esa
authors.initials: E
authors.lastname: Räsänen