arXiv subjects

Guillaume Schull

Publications and source records attributed to Guillaume Schull.

24 records · Page 2Linked to original sources

arXiv2016

Electrically-driven vibronic spectroscopy with sub-molecular resolution

A scanning tunneling microscope is used to generate the electroluminescence of phthalocyanine molecules deposited on NaCl/Ag(111). Photon spectra reveal an intense emission line at 1.9 eV that corresponds to the fluorescence of the molecules, and a series of weaker red-shifted lines. Based on a comparison with Raman spectra acquired on macroscopic molecular crystals, these spectroscopic features can be associated to the vibrational modes of the molecules and provide a detailed chemical fingerprint of the probed species. Maps of the vibronic features reveal sub- molecularly-resolved structures whose patterns are related to the symmetry of the probed vibrational modes.

cond-mat.mes-hall↗

arXiv2015

Pulling and Stretching a Molecular Wire to Tune its Conductance

A scanning tunnelling microscope is used to pull a polythiophene wire from a Au(111) surface while measuring the current traversing the junction. Abrupt current increases measured during the lifting procedure are associated to the detachment of molecular sub-units, in apparent contradiction with the expected exponential decrease of the conductance with wire length. \textit{Ab initio} simulations reproduce the experimental data and demonstrate that this unexpected behavior is due to release of mechanical stress in the wire, paving the way to mechanically gated single-molecule electronic devices.

cond-mat.mes-hall↗

arXiv2014

Electroluminescence from a polythiophene molecular wire suspended in a plasmonic scanning tunneling microscope junction

The electroluminescence of a polythiophene wire suspended between two metallic electrodes is probed using a scanning tunneling microscope. Under positive sample voltage, the spectral and voltage dependencies of the emitted light are consistent with the fluorescence of the wire junction mediated by localized plasmons. This emission is strongly attenuated for the opposite polarity. Both emission mechanism and polarity dependence are similar to what occurs in organic light emitting diodes (OLED) but at the level of a single molecular wire.

cond-mat.mes-hall↗

arXiv2013

Oligothiophene nano-rings as electron resonators for whispering gallery modes

Structural and electronic properties of oligothiophene nano-wires and rings synthesized on a Au(111) surface are investigated by scanning tunneling microscopy. The spectroscopic data of the linear and cyclic oligomers show remarkable differences which, to a first approximation, can be accounted by considering electronic states confinement to one-dimensional (1D) boxes having respectively fixed and periodic boundary conditions. A more detailed analysis shows that polythiophene must be treated as a ribbon (i.e. having an effective width) rather than a purely 1D structure. A fascinating consequence is that the molecular nano-rings act as whispering gallery mode resonators for electrons, opening the way for new applications in quantum-electronics.

cond-mat.mes-hall↗

arXiv2010

Optical Probe of Quantum Shot Noise Reduction at a Single-Atom Contact

Visible and infra-red light emitted at a Ag-Ag(111) junction has been investigated from tunneling to single atom contact conditions with a scanning tunneling microscope. The light intensity varies in a highly nonlinear fashion with the conductance of the junction and exhibits a minimum at conductances close to the conductance quantum. The data are interpreted in terms of current noise at optical frequencies, which is characteristic of partially open transport channels.

quant-ph↗

arXiv2009

Passing current through touching molecules

The charge flow from a single C60 molecule to another one has been probed. The conformation and electronic states of both molecules on the contacting electrodes have been characterized using a cryogenic scanning tunneling microscope. While the contact conductance of a single molecule between two Cu electrodes can vary up to a factor of three depending on electrode geometry, the conductance of the C60-C60 contact is consistently lower by two orders of magnitude. First-principles transport calculations reproduce the experimental results, allow a determination of the actual C60-C60 distances, and identify the essential role of the intermolecular link in bi- and trimolecular chains.

cond-mat.mes-hall↗