VietNam 2013 

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


 Nanophysics: from fundamentals to applications

(the return)


Wednesday 7
Dots and wires

› 16:10 - 16:30 (20min)
Alternance of 0.7 anomaly and Zero Bias Anomaly splitting in Quantum Point Contacts controlled by Scanning Gate Microscopy
Boris Brun  1@  , Frederico Martins  2@  , Sebastien Faniel  2@  , Benoit Hackens  2@  , Vincent Bayot  1@  , Serge Huant  1@  , Ulf Gennser  3@  , Dominique Mailly  3@  , Marc Sanquer  4@  , Hermann Sellier  1@  
1 : Institut Néel  (NEEL)  -  Website
CNRS : UPR2940, Université Joseph Fourier - Grenoble I, Institut National Polytechnique de Grenoble - INPG, Institut National Polytechnique de Grenoble (INPG)
25 avenue des Martyrs - BP 166 38042 GRENOBLE CEDEX 9 -  France
2 : Institut de la matière condensée et des nanosciences / Institute of Condensed Matter and Nanosciences  (IMCN)  -  Website
1/6, Place L. Pasteur -1348 Louvain-la-Neuve -  Belgium
3 : Laboratoire de photonique et de nanostructures  (LPN)
Route de Nozay 91460 MARCOUSSIS -  France
4 : Institut Nanosciences et Cryogénie (ex DRFMC)  (INAC)
Grenoble -  France

Since the first experimental realization of a Quantum Point Contact (QPC), an additional feature to the quantized conductance steps has been observed below the first plateau: the famous "0.7 anomaly". Another strange feature arises at lower temperature: a peak at zero bias in the differential conductance: the "Zero Bias Anomaly". To study these phenomena both supposed to be due to electron-electron interactions, we performed Scanning Gate Microscopy on a QPC, at a base temperature of 20 mK. A negatively charged tip is scanned 35 nm above the sample surface, allowing us to observe well-known interference fringes, as well as new conductance oscillations due to a direct tuning of the QPC potential affecting the many-body states arising in the low conductance regime. With this technique, we observed alternance of the 0.7 anomaly correlated to an alternating splitting of the Zero Bias Anomaly into two peaks as the tip is approached towards the QPC. This observation puts in light the intimate link between these two phenomena and is a crucial result to conclude on the widely debated many-body effects underlying QPCs' physics.

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