"Visualizing electron correlation in nano-objects using a scanning tunneling
microscope: Molecules, quantum dots, carbon nanotubes"
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Scanning tunnelling spectroscopy (STS) visualizes electron states in both
extended systems and nano-objects, such as quantum dots, molecules, carbon
nanotubes. Whereas extended quantum states are insensitive to electron number
fluctuations, an energy gap opens each time a new electron is injected by the
STS tip into a nano-object. This gap originates from the interaction of the next
incoming electron with the others already present in the system. Under this
Coulomb blockade condition, STS maps the wave function modulus of the electron
injected by the tip into the nano-object. The obtained image is routinely
interpreted as the atomic-like or molecular orbital of the added electron, that
experiences the mean field of the other electrons already populating the system.
A fundamental question is whether features of the tunnelling map may appear due
to electron-electron correlation beyond mean field [1]. In this talk I will
demonstrate that the answer is positive, focusing on planar molecules with metal
centres [2], semiconductor quantum dots [3], quantum wires and carbon nanotubes [4].  
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[1] M. Rontani and E. Molinari, Phys. Rev. B 71, 233106 (2005); M. Rontani,
Nature Mat. 10, 173 (2011).
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[2] D. Toroz, M. Rontani, and S. Corni, J. Chem. Phys. 134, 024104 (2011); Phys.
Rev. Lett. 110, 018305 (2013).
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[3] G. Maruccio, M. Janson, A. Schramm, C. Meyer, T. Matsui, C. Heyn, W. Hansen,
R. Wiesendanger, M. Rontani, and E. Molinari, Nano Lett. 7, 2701 (2007).
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[4] A. Secchi and M. Rontani, Phys. Rev. B 85, 121410(R) (2012).