download report - Sapienza

More documents

Recommendations

Info

Scientific Report 2007-2009 Condensed matter physics and biophysics (or macromolecules attached to them) is offered by the so-called optical tweezers. Optical forces are indeed ideally suited to manipulate matter at the mesoscale which is characterised by length scales ranging from ten nanometers to hundreds of micrometers, femtonewton to nanonewton forces, and time scales from the microsecond on. In Rome we have built a set-up to perform holographic optical trapping (HOT), focusing an engineered wavefront into a tiny hologram image made of bright light spots in 3D, each spot serving as an independent point trap, providing contactless micromanipulation technique with many body, dynamic, 3D capabilities (C30). A large effort is also devoted to investigation of electronic properties of novel materials, mostly semiconductor and organometallic compounds. Indeed, the synthesis of nanostructured semiconductors is incessantly boosting the number of opportunities in the field of electronics and photonics, as well as in the investigation of fundamental quantum phenomena in top-bench experiments. The control and modification of the physical properties of semiconductor heterostructures at nanometre scale lengths is thus crucial. In Rome, we presently focus on magneto-photoluminescence (m-PL) experiments, a powerful method to investigate fundamental properties of novel semiconductor materials such as Ga(As,N) (an example of a dilute nitrides), which feature surprising physical properties and qualitatively new alloy phenomena, e.g., a giant negative bowing of the band gap energy and a large deformation of the conduction band structure (C31). Moreover, we discovered that hydrogen irradiation of GaAsN completely neutralizes the effect of N and transforms GaAsN into virtual GaAs, with relevant changes in the energy gap and electron effective mass, among others. This has opened a novel way to the defect engineering of dilute nitrides, where it is possible to realize nanostructures on demand (C32). Recently, organic molecules have been fruitfully exploited to develop devices with specific functionalities. Engineering of these devices requires an atomic level understanding of the parameters that control the structure and the function of these low-dimensional molecular architectures. A crucial issue for these organic-inorganic systems is the achievement of long-range order in exotic configurations (two-dimensional arrays, one-dimensional wires) such as to allow formation of exemplary hybrid structures with peculiar electronic properties associated to the reduced dimensions. We investigate organometallic molecules (like pentacene or metal-phthalocyanines, MPc) assembled on suitable crystalline surfaces in 1D chains or 2D ordered phases, with the final goal to design, control and optimize the electronic, transport and magnetic properties. In particular, a model to describe the interface dipole, the electronic state diagram, the bandwidth and the electronic state dispersion for the organic heterojunctions and organic-inorganic interfaces has been experimentally and theoretically proved (C33,C34). Furthermore, MPc formed by a magnetic central atoms are being used as chemical ”cage” for anchoring the magnetic ion to a metal surface, such as the spin-state of the central atom could couple with the underlying magnetic or non magnetic metal. Materials are not only studied under ambient conditions, but also under extreme perturbations. The development of modern pressure cells had made possible to investigate structural and electronic properties of materials under high pressure. One interesting case is offered by the possibility to modulate the electron-phonon coupling via modification of the lattice parameters, with the aim of investigating the physics of strongly correlated systems, which as we have discussed at the beginning represents one of the most challenging tasks of condensed-matter research (C35). Another case is offered by low-dimensional systems where the external variables (like temperature, magnetic field, and chemical and applied pressure) can affect the dimensionality of the interacting electron gas, and thus the intrinsic electronic properties, as well as the interplay among different order parameters, giving rise to rich phase diagrams (C36). In many scientific fields considerable efforts are devoted to engeneering new materials with specific permittivity ϵ eff and magnetic permeability µ eff , to be able to control different properties of the electromagnetic radiation. A recent approach is based on artificial materials structures (metamaterials, MM) constituted of a macroscopic (periodic or aperiodic) arrays of single elements: <strong>Sapienza</strong> Università di Roma 51 Dipartimento di Fisica
Scientific Report 2007-2009 Condensed matter physics and biophysics the size and the spacing between elements are much smaller than the wavelength of the e.m. field incident on them. By appropriate choice of materials and designs, is now possibile to control the behavior of ϵ eff and µ eff therefore to tailor the refractive index n of the MM. In this way, beside artificial magnetism, negative permeability and permittivity, a negative refractive index can be also obtained. Activity is also ongoing on the integration of spintronics and conventional semiconductor technology, opening the way to wide-range applications. The discovery and exploitation of giant magnetoresistance in magnetic multilayers was the first remarkable achievement in spin electronics (spintronics). The second breakthrough was the observation of spin injection in structures containing layers of ferro-magnetic metal (FM) separated by a spacer of non-magnetic semiconductor (NS). Realization of both phenomena in the same FM/NS structures is currently investigated (C37). The possibility of trapping light in disordered materials is expected to foster new applications in the field of energy and medicine, as well as novel fundamental discoveries in applied mathematics and the science of complex systems. A significant effort is devoted to the realization of advanced parallel codes for the analysis of light propagation in disordered materials characterized by various wavelengths, ranging from the Angstrom regime to the visible, Terahertz and the acoustic scale (C38). A significant effort is also directed to the investigation of nanomaterials for alternative energies. Specifically we investigate hydrogen storage, a nodal point for the development of a hydrogen economy, attempting to understand the basic mechanisms of the hydrogenation/dehydrogenation process and the changes induced by nano-confinement, via anelastic spectroscopy and differential scanning calorimetry (C39). We also focus on advanced NMR application to imaging in material, tissues and humans with a wide variety of methods. Molecular imaging offers the possibility of non-invasive visualization in space and time of cellular processes at molecular or genetic level of function. Specifically, we implement Diffusion Tensor (DTI) and Diffusion-weighted (DWI) imaging NMR techniques to provide information on biophysical properties of tissues which inuence the diffusion of water molecules (C40,C41). Being located in Rome, it is inevitable to dedicate attention to the preservation of our cultural heritage. Physics can help significantly the development of non-invasive methodologies for preservation, characterization and diagnostics. Methods dealing with the study of works of art must be effective in producing information on a huge variety of materials (wood, ceramic, paper, resin, pigments, stones, textiles, etc.), must be highly specific owing to the variability of volume and shape of hand-works and must comply with the severe conditions that guarantee their preservation. Therefore, standard spectroscopic methods need to be properly modulated in order to fit such materials, while their application area must be enlarged to include structures and models which are unusual for physicists (C42). Last but not least, we briefly recall the significant ongoing activity in quantum information (C43,C44) and computation. Quantum information is a new scientific field with origins in the early 90s, introduced by the merging of classical information and quantum physics. It is multidisciplinary by nature, with scientists coming from diverse areas in both theoretical and experimental physics (atomic physics, quantum optics and laser physics, condensed matter, etc.) and from other disciplines such as computer science, mathematics, material science and engineering. It has known a huge and rapid growth in the last years, both on the theoretical and the experimental side and has the potential to revolutionize many areas of science and technology. The main goal is to understand the quantum nature of information and to learn how to formulate manipulate, and process it using physical systems that operate on quantum mechanical principles, more precisely on the <strong>Sapienza</strong> Università di Roma 52 Dipartimento di Fisica
Page 2 and 3: Sapienza Università di Roma Dipart
Page 4 and 5: Scientific Report 2007-2009 Introdu
Page 10 and 11: Scientific Report 2007-2009 Organiz
Page 20 and 21: Scientific Report 2007-2009 Theoret
Page 48 and 49: Scientific Report 2007-2009 Condens
Page 102 and 103:
Scientific Report 2007-2009 Particl
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
2 2 2 Scientific Report 2007-2009 P
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Scientific Report 2007-2009 Astrono
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Scientific Report 2007-2009 Geophys
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Scientific Report 2007-2009 History
Page 174 and 175:
Scientific Report 2007-2009 History
Page 176 and 177:
Scientific Report 2007-2009 Laborat
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Scientific Report 2007-2009 Grants
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Scientific Report 2007-2009 Dissemi
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
Page 220 and 221:
Page 222 and 223:
Page 224 and 225:
Page 226 and 227:
Page 228 and 229:
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
Page 254 and 255:
Page 256 and 257:
Page 258 and 259:
Page 260:
show all

download report - Sapienza

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?