VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Wednesday 7
Dots and wires

› 16:30 - 16:50 (20min)
Imaging Fractional Incompressible Stripes in Integer Quantum Hall Systems
Nicola Paradiso  1@  , Stefan Heun  1@  , Stefano Roddaro  1@  , Lucia Sorba  1@  , Giorgio Biasiol  2@  , Fabio Beltram  1@  , Loren Pfeiffer  3@  , K. West  3@  
1 : Scuola Normale Superiore di Pisa  (SNS)  -  Website
Piazza dei Cavalieri 7 56126 PISA -  Italy
2 : Istituto Officina dei Materiali CNR, Laboratorio TASC
Basovizza (TS) -  Italy
3 : Department of Electrical Engineering [Princeton]  (EE)  -  Website
Princeton, NJ, 08544 -  United States

The existence of a fractional order within integer quantum Hall edge channel has been debated for a long time, due to the conflicting results provided by the experiments. In interference experiments, integer edge states seem to behave as monolithic objects with no inner structure. Other experiments, however, clearly highlight the role of fractional substructures.

In the present work, we use scanning gate microscopy (SGM) and demonstrate that fractional features were unambiguously observed in every integer quantum Hall constriction studied. Experiments were performed at bulk filling factor n=1. We brought two integer channels into proximity by means of a quantum point contact (QPC) and used the biased SGM tip to tune backscattering. Plateaus are observed in source-drain differential conductance maps whenever the tip induces an incompressible phase at the QPC center. We present SGM maps which directly reveal the width of the most relevant fractional stripes, as the nu =1/3 shown in the attached Figure (a,b). In our experiments, we observed plateaus corresponding to the filling factors 1/3 and 2/5, together with their particle–hole conjugates 2/3 and 3/5. Our results compare well with predictions of the edge–reconstruction theory.

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