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Speaker: Xiangfeng Duan
Affiliation: UCLA, USA
Abstract Details: Nanoscale integration of dissimilar materials with distinct compositions, structures and properties has the potential to create a new generation of integrated nanosystems with unique functions and/or unprecedented performance that can break the boundaries of traditional technologies. In this talk, I will first give a brief overview of diverse opportunities enabled by nanoscale integration of a wide range of 0D, 1D and 2D nanostructures, and then I will focus my discussions on the hetero-integration of graphene with a variety of nano and molecular scale structures to demonstrate the power and versatility material integration at nanoscale. A few examples will be discussed, including the integration of graphene with a self-aligned nanowire gate to create the highest speed graphene transistors, vertical integration of graphene with other layered materials to create multi-heterostructures for logic devices, integration of graphene with plasmonic nanostructures to create multi-color high speed photodetectors, and integration of graphene with various planar π-conjugating molecules for band gap engineering, molecular sensing and catalysis.
About the Speaker: Dr. Duan received the B.S degree in chemistry from University of Science and Technology and China (USTC) in 1997, M.A. degree in chemistry and Ph.D. degree in physical chemistry from Harvard University in 1999 and 2002, respectively. He was a Founding Scientist, Principal Scientist and Manager of Advanced Technology at Nanosys Inc. from 2002 to 2008. He joined UCLA in 2008.
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Speaker: Javier Aizpurua
Affiliation: Donostia International Physics Center
Abstract Details: Plasmonic nanostructures can be used as canonical building blocks to host and actively participate in a variety of complex physical phenomena such as non-linear effects, quantum tunneling or photoemission, to cite a few. We will present a number of examples where a conductive contact between the two arms of a gap-antenna is used for (i) effective control of the near-field oscillations in the loaded antenna [1], (ii) relating transport and optical properties based on the evolution of the Plasmon excitations [2], and (iii) producing optical spectral switch based on the presence of a photoconductive material linking the gap that can sustain a fast and large free-carrier density [3]. Plasmonic nanostructures can be used as canonical building blocks to host and actively participate in a variety of complex physical phenomena such as non-linear effects, quantum tunneling or photoemission, to cite a few. We will present a number of examples where a conductive contact between the two arms of a gap-antenna is used for (i) effective control of the near-field oscillations in the loaded antenna [1], (ii) relating transport and optical properties based on the evolution of the Plasmon excitations [2], and (iii) producing optical spectral switch based on the presence of a photoconductive material linking the gap that can sustain a fast and large free-carrier density [3]. References: [1] M. Schnell, A. García-Etxarri, A.J. Huber, K. Crozier, J. Aizpurua, R. Hillenbrand, Nature Photonics 3, 287 (2009). [2] O. Pérez-González, N. Zabala, A.G. Borisov, N. J. Halas, P. Nordlander, J. Aizpurua, Nano Lett. 10, 3090 (2010) [3] N. Large, M. Abb, J. Aizpurua, O. Muskens, Nano Lett. 10, 1741 (2010) [4] R. Esteban, A.G. Borisov, P. Nordlander, J. Aizpurua, Nature Comm. 3, 825 (2012).
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Speaker: Gleb YUSHIN
Affiliation: Georgia Institute of Technology, USA
Abstract Details: High power energy storage devices, such as supercapacitors and Li-ion batteries, are critical for the development of zero-emission electrical vehicles, large scale smart grid, and energy efficient cargo ships and locomotives. The energy storage characteristics of supercapacitors and Li-ion batteries are mostly determined by the specific capacities of their electrodes, while their power characteristics are influenced by the maximum rate of the ion transport. The talk will focus on the development of Graphene, Carbon nanocomposite electrodes capable to improve both the energy and power storage characteristic s of the state of the art devices. Carbon-polymer and carbon-metal oxide nanocomposites have been demonstrated to greatly exceed the specific capacitance of traditional electrodes for supercapacitors. Selected materials showed the unprecedented ultra-fast charging and discharging characteristics. Intelligently designed silicon-carbon-polymer composites showed up to 8 times higher specific capacity than graphite, the conventional anode material in Li-ion batteries, and stable performance for over 1000 cycles. In order to overcome the limitations of traditional composites precise control over the materials’ structure and porosity at the nanoscale was required.
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Speaker: Prof. Giulio Casati
Affiliation: Center for Complex Systems, CNR-INFM and University of Insubria at Como
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Speaker: Oleg P. Sushkov
Affiliation: School of Physics, Univ. New South Wales
Abstract Details: The phase diagrams of LSCO and YBCO in spite of similarities are remarkably different at low doping. Both the electric conduction properties and the commensurate/incommensurate spin ordering properties differ very significantly. The role of disorder in YBCO is insignificant while the bilayer structure is crucial. On the other hand, in LSCO the intrinsic disorder qualitatively influences the properties of the system. Understanding of reasons for the differences provides an insight into generic physics of an ideal cuprate plane. YBCO is the most important testing ground since it is practically unaffected by disorder. The compound has two magnetic quantum critical points (QCP) located at doping x1=0.06 and x2=0.09. At doping below the QCP1 the compound is a collinear antiferromagnet and also a normal conductor with a finite resistivity at zero temperature. The value of the staggered magnetization at zero temperature is 0.6muB, the maximum value allowed by spin quantum fluctuations. The staggered magnetization is practically independent of doping. At x > x1 the incommensurate spin spiral is developing and simultaneously the static component of the magnetization is quickly decaying with doping. The static magnetization goes to zero at the QCP2. At x > x2 the spin spiral becomes fully dynamic. I overview the bulk of experimental data and describe how these properties are explained and predicted by the theory. The present analysis demonstrates that the superconductivity is related to the spin spiral ordering.
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Speaker: Dr. Jose L. Garcia-Palacios
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Speaker: Dr Choonkyu Hwang
Affiliation: Lawrence Berkeley National Laboratory, Berkeley, USA
Abstract Details:

Graphene is a wonderful material in many aspects. This thinnest and strongest material possesses a simple geometric structure, but exhibits beautiful physical properties based on its massless Dirac Fermionic behavior. Its charge carrier can travel with huge mobility approaching ballistic transport regime. Graphene under certain conditions is expected to show spin polarized electric current holding significant promise for future spintronic devices. In this talk, I will discuss the potential of graphene technology in terms of two different fundamental aspects, magnetic and electronic properties, mainly based on Angle-resolved photoemission spectroscopy (ARPES) studies. First, despite a lot of theoretical studies on magnetic graphene, long range order of local magnets and detailed experimental studies on the magnetism are still in a veil. I will show our recent studies on the first direct evidence of complex spin texture in a carbon-based system, which will be of great interests not only in realizing ferromagnetic quantum Hall effect and other strongly correlated electronic states, but also giving intriguing insight on the realization of graphene based spintronic devices. Second, charge carriers in graphene are expected to show clear deviation from normal Fermi liquids. Hence, Fermi velocity, an important ingredient of electronic properties, can be controlled by changing electronic correlations. I will show that electronic correlations and resultant Fermi velocity can be controlled simply via a substrate hosting graphene on it, which provides not only a completely new route to control electronic properties, but also a straightforward evidence of non-Fermionic behavior of charge carriers in graphene.

About the Speaker:

Ph.D. in Physics, 2008 at Pohang University of Science and Technology. Post-doctoral fellow at Lawrence Berkeley National Laboratory. Research interests are strongly correlated physics in graphene and new experimental techniques based on ARPES, such as time-resolved, gated, and spin-resolved ARPES.

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Speaker: Christian A. Nijhuis
Abstract Details:

Understanding the mechanisms of charge transport across molecules, or self-assembled monolayers, is important in organic based photovoltaics, OLEDs, energy storage, bio-electronic devices, etc. Issues regarding how molecular orbitals couple to the electrodes, or the influence of subtle changes of the intermolecular interactions between the molecules in the SAMs, on the performance of molecular electronic devices has rarely experimentally been addressed.

We identified a molecular diode: junctions with SAMs of S(CH2)11Fc, i.e., SAMs with ferrocene at the top, on ultra-flat Ag bottom-electrodes contacted with EGaIn (an eutectic alloy of Ga and In) top-electrodes rectified currents with a rectification ratio of 100, while those junctions with SAMs of S(CH2)10CH3, i.e, SAMs without Fc units, did not rectify.1,2

To study the influence of subtle changes in the intermolecular interactions between the molecules in the SAMs, and the coupling of the molecular orbitals with the electrodes, we fabricated devices with a series molecules of the type S(CH2)nFc (with n = 3, 4, …, 15) and SCnFcCn-13 (with n = 1, 2, 3, …, 15), respectively. We found that devices with n is odd are ten times better diodes than those devices with n = even. This so-called odd-even effect originates from small changes in the structures of the SAMs, which, in turn, depends on the interactions between the molecules in the SAM. By controlling the coupling of the molecular orbitals with the electrodes, we succeeded at "turning" around a diode at the molecular level. Thus, we are able to control the direction of rectification at the molecular level.

References

1) Nijhuis, C. A.; Reus, W. F.; Barber, J.; Dickey, M. D.; Whitesides, G. M. Nano Lett. 2010, 10, 3611.2) Nijhuis, C. A.; Reus, W. F.; Siegel, A. C.; Whitesides, G. M. J. Am. Chem. Soc. 2011, 133, 15397

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Speaker: Alexandre Pachoud
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