ORCID Profile
0000-0001-5733-515X
Current Organisations
University of Udine
,
Università degli Studi di Udine
,
Centre National de la Recherche Scientifique
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Publisher: Springer Science and Business Media LLC
Date: 11-03-2013
DOI: 10.1038/SREP01416
Abstract: The unique properties of quantum hall devices arise from the ideal one-dimensional edge states that form in a two-dimensional electron system at high magnetic field. Tunnelling between edge states across a quantum point contact (QPC) has already revealed rich physics, like fractionally charged excitations, or chiral Luttinger liquid. Thanks to scanning gate microscopy, we show that a single QPC can turn into an interferometer for specific potential landscapes. Spectroscopy, magnetic field and temperature dependences of electron transport reveal a quantitatively consistent interferometric behavior of the studied QPC. To explain this unexpected behavior, we put forward a new model which relies on the presence of a quantum Hall island at the centre of the constriction as well as on different tunnelling paths surrounding the island, thereby creating a new type of interferometer. This work sets the ground for new device concepts based on coherent tunnelling.
Publisher: Springer Science and Business Media LLC
Date: 09-2201
DOI: 10.1038/NCOMMS1038
Abstract: In the quantum Hall regime, near integer filling factors, electrons should only be transmitted through spatially separated edge states. However, in mesoscopic systems, electronic transmission turns out to be more complex, giving rise to a large spectrum of magnetoresistance oscillations. To explain these observations, recent models put forward the theory that, as edge states come close to each other, electrons can hop between counterpropagating edge channels, or tunnel through Coulomb islands. Here, we use scanning gate microscopy to demonstrate the presence of QH Coulomb islands, and reveal the spatial structure of transport inside a QH interferometer. Locations of electron islands are found by modulating the tunnelling between edge states and confined electron orbits. Tuning the magnetic field, we unveil a continuous evolution of active electron islands. This allows to decrypt the complexity of high-magnetic-field magnetoresistance oscillations, and opens the way to further local-scale manipulations of QH localized states.
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4848369
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4848404
Publisher: American Physical Society (APS)
Date: 25-02-2015
Publisher: American Physical Society (APS)
Date: 28-09-2007
Publisher: American Physical Society (APS)
Date: 10-03-2008
Publisher: Springer Science and Business Media LLC
Date: 14-02-2018
DOI: 10.1038/S41598-018-21250-Y
Abstract: A counter-intuitive behavior analogous to the Braess paradox is encountered in a two-terminal mesoscopic network patterned in a two-dimensional electron system (2DES). Decreasing locally the electron density of one channel of the network paradoxically leads to an increased network electrical conductance. Our low temperature scanning gate microscopy experiments reveal different occurrences of such puzzling conductance variations, thanks to tip-induced localized modifications of electron flow throughout the network’s channels in the ballistic and coherent regime of transport. The robustness of the puzzling behavior is inspected by varying the global 2DES density, magnetic field and the tip-surface distance. Depending on the overall 2DES density, we show that either Coulomb Blockade resonances due to disorder-induced localized states or Fabry-Perot interferences tuned by the tip-induced electrostatic perturbation are at the origin of transport inefficiencies in the network, which are lifted when gradually closing one channel of the network with the tip.
Publisher: Springer Science and Business Media LLC
Date: 22-08-2012
Abstract: The Braess paradox, known for traffic and other classical networks, lies in the fact that adding a new route to a congested network in an attempt to relieve congestion can degrade counterintuitively the overall network performance. Recently, we have extended the concept of the Braess paradox to semiconductor mesoscopic networks, whose transport properties are governed by quantum physics. In this paper, we demonstrate theoretically that, alike in classical systems, congestion plays a key role in the occurrence of a Braess paradox in mesoscopic networks.
Publisher: IOP Publishing
Date: 08-04-2011
Publisher: American Physical Society (APS)
Date: 13-02-2012
Publisher: IOP Publishing
Date: 10-06-2009
DOI: 10.1088/0957-4484/20/26/264021
Abstract: We study scanning gate microscopy (SGM) in open quantum rings obtained from buried semiconductor InGaAs/InAlAs heterostructures. By performing a theoretical analysis based on the Keldysh-Green function approach we interpret the radial fringes observed in experiments as the effect of randomly distributed charged defects. We associate SGM conductance images with the local density of states (LDOS) of the system. We show that such an association cannot be made with the current density distribution. By varying an external magnetic field we are able to reproduce recursive quasi-classical orbits in LDOS and conductance images, which bear the same periodicity as the Aharonov-Bohm effect.
Publisher: Institute of Physics, Polish Academy of Sciences
Date: 05-2011
Publisher: IOP Publishing
Date: 18-01-2013
Publisher: Springer Berlin Heidelberg
Date: 29-08-2013
No related grants have been discovered for Marco Pala.