Jing Li

Jing Li
Institut Néel, CNRS and Grenoble Alpes University
Equipe : Théorie de la matière condensée
Tuesday, October 24th 11.30 am/ Salle du conseil LCI

Abstract:
The description of the electronic and optical properties of complex supramolecular systems such as
those of interest in organic electronics represents a severe challenge for first principles techniques,
owing to the large molecular dimensions and to the ubiquitous presence of disorder. We will report
on our original hybrid QM/MM scheme merging many-body perturbation theory (GW formalism
and Bethe-Salpeter equation) with accurate classical polarizable models of atomistic resolution. Our
results for bulk pentacene prove that the gap is insensitive to the partitioning of molecules in QM
and MM subsystems, as a result of the mutual compensation of quantum and classical
polarizabilities, clarifying the relation between polarization energy and charge delocalization. Our
embedded GW calculations, are capable to accurately describe ionization energies and electron
affinities at crystal surfaces of penatcene and perfluoropentacene from first principles.

The electronic and optical properties of the paradigmatic F4TCNQ-doped pentacene in the lowdoping
limit are investigated by a combination of state-of-the-art GW and Berthe-Salpeter manybody
ab initio methods accounting for environmental screening effects, and a carefully
parametrized model Hamiltonian. We demonstrate that while the acceptor level lies very deep in the
gap, the inclusion of electron-hole interactions strongly stabilizes dopant-semiconductor charge
transfer states and, together with spin statistics and structural relaxation effects, rationalize the
possibility for room-temperature dopant ionization. Our findings reconcile available experimental
data, shedding light on the partial vs. full charge transfer scenario discussed in the literature, and
question the relevance of the standard classification in shallow or deep impurity levels prevailing
for inorganic semiconductors.

References :
J. Li, G. D’Avino, I. Duchemin, D. Beljonne, X. Blase, J. Phys. Chem. Lett. 7, 2814 (2016)
J. Li, G. D’Avino, A. Pershin, D. Jacquemin , I. Duchemin, D. Beljonne, X. Blase, Phys. Rev.
Materials, 1, 025602 (2017)

Amin Arbabian
Assistant Professor, Department of Electrical Engineering
Stanford University
Wednesday, October 18th 11am / IEMN Amphitheater

Abstract:
Commercial mm-wave systems are addressing a variety of applications in communication and radar. However, scaling of these systems to larger throughputs and spatial coverage is limited by hardware constraints. This work explores challenges in the silicon integration of scalable high-throughput “Wireless Fiber’’ links that use the spatial and spectral degrees of freedom by exploiting multiplexing in LoS MIMO environments and at extremely high bandwidths. We examine tradeoffs in the partitioning of functionality between the transmitter and receiver as well as the analog and digital domains and investigate a new scalable analog processing architecture for the receiver network. The design of a 4×4 160 Gbps system will be discussed. In addition to this system, we will also present an energy-efficient 130GHz 12.5Gbps OOK system operating with 1.55pJ/bit/m at >5m range. Mm-wave plastic dielectric waveguides for high-speed links and signal distribution in mm-wave systems will also be discussed.

Short Bio:
Amin Arbabian received his Ph.D. degree in EECS from UC Berkeley in 2011 and in 2012 joined Stanford University, as an Assistant Professor of Electrical Engineering. His research interests are in mm-wave and high-frequency circuits and systems, imaging technologies, and ultra-low power sensors and implantable devices. Prof. Arbabian currently serves on the steering committee of RFIC, the technical program committees of RFIC and ESSCIRC, and as associate editor of the IEEE Solid-State Circuits Letters (SSC-L) and the IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology (J-ERM). He is the recipient or co-recipient of the 2016 Stanford University Tau Beta Pi Award for Excellence in Undergraduate Teaching, 2015 NSF CAREER award, 2014 DARPA Young Faculty Award (YFA) including the Director’s Fellowship in 2016, 2013 Hellman faculty scholarship, and best paper awards from several conferences including ISSCC (2010), VLSI Circuits (2014), RFIC symposium (2nd place, 2008 and 2011), ICUWB (2013), PIERS (2015), and the MTT-S BioWireless symposium (2016).