Laboratorio Nazionale TASC INFM

Trieste, Italy

Laboratorio Nazionale TASC INFM

Trieste, Italy
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MacOvez R.,Zernike Institute for Advanced Materials | MacOvez R.,ICFO - Institute of Photonic Sciences | Hunt M.R.C.,Durham University | Goldoni A.,Elettra - Sincrotrone Trieste | And 3 more authors.
Journal of Electron Spectroscopy and Related Phenomena | Year: 2011

We report a combined photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES) study of distilled, phase pure films of C 60 and the monomeric fullerides Cs6C60, Cs 4C60 and fcc RbC60. The separation between the highest energy PES and lowest energy IPES features, which is a measure of the barrier to hopping, is 1.45 eV in Cs4C60 and 0.7 eV in RbC60. This difference is large enough to explain, in a correlated electron picture, the reported differences in electronic mobility between the two stoichoimetries. From the PES-IPES energy separation, the value of the Hubbard U is estimated to be 1.5 eV in closed-shell C60 and Cs 6C60, while in Cs4C60 and RbC 60 such value is reduced to ∼1 and 0.7 eV, respectively. This trend can be only partially understood taking into account the different molecular polarizability and crystal structure of the various stoichiometries. The relatively low values found for open-shell compounds indicate that the bulk Hubbard U is smaller in open-shell fullerides than usually believed, which might help explain superconductivity and the observation of spin-singlets in odd-stoichiometry fullerides. © 2010 Elsevier B.V. All rights reserved.

Burresi M.,CNR Institute of Applied Physics Nello Carrara | Burresi M.,CNR Institute of Neuroscience | Pratesi F.,CNR Institute of Applied Physics Nello Carrara | Vynck K.,CNR Institute of Applied Physics Nello Carrara | And 5 more authors.
2013 Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, CLEO/Europe-IQEC 2013 | Year: 2013

The quest for efficient harvesting of solar radiation is one of the major areas of research in the renewable energy field. Through different photonic architectures it is possible to augment the optical absorption by trapping light within thin and ultra-thin films, the latter being desirable to decrease costs and efficiently extract the photogenerated charge carriers. Engineering the absorbing material at the nanoscale indeed leads to interferences that can significantly increase light absorption [1]. © 2013 IEEE.

Wu L.S.,State University of New York at Stony Brook | Janssen Y.,Broohaven National Laboratory | Marques C.,State University of New York at Stony Brook | Bennett M.C.,Broohaven National Laboratory | And 11 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present measurements of the specific heat, magnetization, magnetocaloric effect, and magnetic neutron diffraction carried out on single crystals of antiferromagnetic Yb3Pt4, where highly localized Yb moments order at TN=2.4 K in zero field. The antiferromagnetic order was suppressed to TN→0 by applying a field of 1.85 T in the ab plane. Magnetocaloric effect measurements show that the antiferromagnetic phase transition is always continuous for TN0, although a pronounced step in the magnetization is observed at the critical field in both neutron diffraction and magnetization measurements. These steps sharpen with decreasing temperature, but the related divergences in the magnetic susceptibility are cut off at the lowest temperatures, where the phase line itself becomes vertical in the field-temperature plane. As TN→0, the antiferromagnetic transition is increasingly influenced by a quantum critical end point, where TN ultimately vanishes in a first-order phase transition. © 2011 American Physical Society.

Paradiso N.,CNR Institute of Neuroscience | Heun S.,CNR Institute of Neuroscience | Roddaro S.,CNR Institute of Neuroscience | Pfeiffer L.N.,Bell Laboratories | And 5 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2010

Electronic Mach-Zehnder interferometers in the quantum Hall (QH) regime are currently discussed for the realization of quantum information schemes. A recently proposed device architecture employs interference between two co-propagating edge channels. Here we demonstrate the precise control of individual edge-channel trajectories in quantum point contact devices in the QH regime. The biased tip of an atomic force microscope is used as a moveable local gate to pilot individual edge channels. Our results are discussed in light of the implementation of multi-edge interferometers. © 2009 Elsevier B.V. All rights reserved.

Kumar M.,Allahabad University | Kumar M.,Laboratorio Nazionale TASC INFM | Rajput P.,UGC-DAE Consortium for Scientific Research | Khan S.A.,Inter University Accelerator Center | And 2 more authors.
Applied Surface Science | Year: 2010

Influence of substrate on electronic sputtering of fluoride (LiF, CaF2 and BaF2) thin films, 10 and 100 nm thin, under dense electronic excitation of 120 MeV Ag25+ ions irradiation is investigated. The sputtering yield of the films deposited on insulating (glass) and semiconducting (Si) substrates are determined by elastic recoil detection analysis technique. Results revealed that sputtering yield is higher, up to 7.4 × 106 atoms/ion for LiF film on glass substrate, than that is reported for bulk materials/crystals (∼104 atoms/ion), while a lower value of the yield (2.3 × 106 atoms/ion) is observed for film deposited on Si substrate. The increase in the yield for thin films as compared to bulk material is a combined effect of the insulator substrate used for deposition and reduced film dimension. The results are explained in the framework of thermal spike model along with substrate and size effects in thin films. It is also observed that the material with higher band gap showed higher sputtering yield. © 2009 Elsevier B.V. All rights reserved.

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