Electron phase shift at the zero-bias anomaly of quantum point contacts
  The Kondo effect is the many-body screening of a local spin by a cloud of electrons at very low temperature. It has been proposed as an explanation of the zero-bias anomaly in quantum point contacts where interactions drive a spontaneous charge localization. However, the Kondo origin of this anomaly remains under debate, and additional experimental evidence is necessary. Here we report on the first phase-sensitive measurement of the zero-bias anomaly in quantum point contacts using a scanning gate microscope to create an electronic interferometer. We observe an abrupt shift of the interference fringes by half a period in the bias range of the zero-bias anomaly, a behavior which cannot be reproduced by single-particle models. We instead relate it to the phase shift experienced by electrons scattering off a Kondo system. Our experiment therefore provides new evidence of this many-body effect in quantum point contacts. 
B. Brun, F. Martins, S. Faniel, B. Hackens, A. Cavanna, C. Ulysse, A.   Ouerghi, U. Gennser, D. Mailly, P. Simon, S. Huant, ...
cond-mat.mes-hall cond-mat.str-el