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I am currently a member of the Foundry's Theory group working under the supervision of Jeffrey B. Neaton.

Research Interests

My research interests are focused on the development and the implementation of new ab initio methodologies in the field of quantum transport; and their application to the tremendous problem of energy transport at the nanoscale.

The Holy Grail of this field is to predict the out-of-equilibrium optical and transport properties of nanoscale interfaces, simply starting from its atomic configuration and the quantum mechanics equations.

Such an understanding would have considerable implications in drawing on a quantitative picture of the fundamental nonequilibrium electronic structure underlying key processes in solar energy conversion - absorption, charge separation, charge transport, and charge collection under operative conditions.

Current projects

More specifically, my ongoing projects at the Molecular Foundry, founded by the Helios project, are focused on:

• The theoretical description of electronic transport properties of nanojunctions in the presence of light. A systematic "first-principles" method to address this essential problem is still missing, and would provide new insights in the field of third-generation photovoltaic technologies. We have developed such a method, based on Non-equilibrium Green's functions theory.
• The finite-bias properties of single-molecule junctions. Recently, some experiments reported a statiscal measurement of the transport properties of single-molecule junctions. Using intensive modeling of the out-of-equilibrium transport properties of the junction, we are working on drawing on a systematic picture of the effect of finite bias at the nanoscale.
• The rectification properties in a single-molecule junction. Rectification -the asymmetry in transport properties under opposite biases- is a useful probe of silicon solar cell, allowing with a minimal apparatus the measurement of their Open-Circuit Voltage. Such a probe at the nanoscale would have considerable applications in the characterization and design of solar cells.
• Single molecule photovoltaics. Together with Peter Doak, PhD student at the foundry, we are investigating the electronic structure and the subsequent optical and transport properties of the simplest solar cell: a single molecule coupled to metal electrodes.

Complementary to the use of well-established Landauer formalisms, we are using a "real-time" framework for computing the quantum transport properties of nanoscale junctions, which has been recently proposed by Di Ventra and Todorov.

Keywords:

• Quantum transport: Semiclassical theory, Landauer Formalism, NEGF.
• Theories: Many-Body: GW Approximation, Bethe Salpeter equation, Keldish formulation of Non Equilibrium Green’s Functions Theory (NEGF), Renormalisation effects, Excited State Lifetimes. Time Dependent Density Functional Theory.
• Systems: Graphene, Nanojunctions, Third-generation solar cells.

Previous projects

• Inclusion of many-body electron-electron interaction and correlation effects on Quantum transport beyond Landauer formalism, by an ab initio GW Self-energy in the framework of NEGF.
• Development and implementation of a new recursion method to calculate in an exact way contact resistance effects.
• Theory of magnetotransport properties of ”bulk” epitaxial graphene, and explanation of the weakness of Shubnikov de Haas oscillations and the quenching of quantum Hall effect.
• Theory of electronic transport properties of graphene nanojunctions, and optical analogies in contact resistance phenomena.

Selected Publications

• Pierre Darancet, Valerio Olevano, and Didier Mayou,
  "Quantum transport through resistive nanocontacts: Effective one-dimensional theory and conductance formulas for nonballistic leads",
  Phys. Rev. B 81, 155422 (2010)
• Pierre Darancet, Valerio Olevano, and Didier Mayou
  "Coherent Electronic Transport through Graphene Constrictions: Subwavelength Regime and Optical Analogy",
  Phys. Rev. Lett. 102, 136803 (2009)
• Pierre Darancet, Nicolas Wipf, Claire Berger, Walt A. de Heer, and Didier Mayou,
  "Quenching of the Quantum Hall Effect in Multilayered Epitaxial Graphene: The Role of Undoped Planes ",
  Phys. Rev. Lett. 101, 116806 (2008).
• Pierre Darancet, Andrea Ferretti, Didier Mayou, and Valerio Olevano,
  "Ab initio GW electron-electron interaction effects in quantum transport",
  Phys. Rev. B 75, 075102 (2007).