cfaed Seminar Series
Prof. Christian Joachim , GNS-CEMES-CNRS; 2MANA, National Institute for Material Sciences; TU Dresden, cfaed
Super tunneling
13.12.2017 (Wednesday)
, 09:30 - 11:00
TU Dresden, HAL building , Hallwachsstr. 3 , 01069 Dresden
Abstract
At low bias voltage and in its HOMO-LUMO energy gap interval, the conductance of a molecular wire decays exponentially while increasing its length. The same phenomenon occurs with a surface dangling bond atomic wire. The corresponding inverse decay length β of this through bond tunneling phenomenon ranges for example from β = 1.2 A-1 for an alkane molecular wire to about β = 0.2 A-1 for a medium large HOMO-LUMO gap χ conjugated molecular wire. As a function of χ and of the effective mass m* of the tunneling electrons, β varies following a universal monotonic decay law. For a given χ, we will discuss (1) what prevents β to be exactly zero that is reaching what can be named a super tunneling transport regime, (2) how to approach a minimum β value by a good choice of the chemical composition of the molecular wire.
Bio
Christian Joachim is Director of Research Fellow (CNRS) at the Nanoscience group CEMES/CNRS and also since 2008 adjunct Professor of Quantum Physics and Quantum Engineering at ISAE Toulouse. He was A*STAR VIP Atom Tech in Singapore (2005-2014) and is now WPI MANA-NIMS in Toulouse and Tsukuba since 2008. He had coordinated the Integrated European projects "Bottom-up Nanomachines", “Pico-Inside” and “AtMol” (2011-2014) with the objective to construct the first ever molecular chip.
Dr Joachim pioneered experimental researches in IBM T.J. Watson and Zurich Labs on electrical contact on a single molecule using the Scanning Tunnelling Microscope (STM). He did STM works from single molecule switching in 1987 to electronic contact on a single C60 molecule in 1995. He introduced the Elastic Scattering Quantum Chemistry (ESQC) technique in 1991, now a standard in STM image and tunnel transport calculations with its multi-electrodes K-ESQC generalization in years 2000 using a full valence basis set. Some accomplishments include: the discovery of long range tunnel processes through a molecule giving rise to the new super tunnel effect, the theory of atomic and molecular manipulation with the STM, the nanofabrication of metal-insulator-metal nano-junctions down to 2 nm for the planar implementation of molecular devices, the invention of a single molecule amplifier in 1997 and the discovery of the first molecule rotor in 1998. In 2001, he designed the first uni-molecular “wheelbarrow” (2 front wheels and to rear legs) 1.6 nm in dimension. More recently, he finalized the
concept of mono-molecular electronics (both semi-classical and quantum) to embed a Boolean logic function with the design of a ½ adder on a single molecule in 2017. He is now developing the atomic scale technology for interconnecting a single molecule (or an atomic scale electronic circuit) to multiple atomic scale electrodes, (precision better than 0.01 nm) using the first in the world LT-UHV 4 STM instrument. In April 2017, he had organized the first ever international nanocar race on this instrument.
With more than 300 scientific publications (h-index = 56), he presented over 360 invited talks on electron transfer through a molecule, STM and Atomic Force Microscopy (AFM) image calculations, tunnel transport through a molecule, single molecule logic gate, atomic scale circuits, atomic scale electronics interconnects and single molecule-mechanical machines. He received a number of prizes for his work in nanoscience and nanotechnology:
• 1988 French Chemical Physics Prize for his work on electron transfer theory
• 1991 IBM France Prize for his work on tunnelling through a molecule
• 1997 Feynman Prize “Experimental” for his work on single molecule manipulation
• 1999 French Nanotechnology prize for his work on nanoscale science
• 2000 IBM Corporation’s Share University Research (SUR) Award
• 2001 CNRS Silver Medal in Chemistry for his work on molecular nanosciences.
• 2004 Elected Fellow of the Institute of Physics, London
• 2005 Feynman Prize “Theoretical” for its design of mono-molecular devices.
He is at the origin and editor of the Springer Series “Advances in Atom and Single Molecule machines” with 10 volumes published since 2012. His book: “Nanosciences, the invisible revolution” (Le Seuil (2008), World Scientific (2009)) is describing the history of nanosciences and its political drawbacks to a general public. He was awarded a Guinness book entry (2011) for the smallest ever functioning nano-gear (1.2 nm in diameter) and in 2015 a “Star of Europe” for European projects coordination. He is a permanent member of the Toulouse Academy of “Sciences et Belles Lettres”.