The activities of our faculty members in Experimental Condensed
Matter Physics are quite varied, covering a full range of frontier
Professor Herman Z. Cummins directs a program of laser light-scattering studies of liquids and solids. His major effort is in the study of phase transitions and critical phenomena, most recently involving the liquid-glass transition, using Raman and Brillouin scattering and photon correlation spectroscopy. Professor Cummins also uses dielectric measurements and participates in neutron-scattering experiments at NIST and at Brookhaven National Laboratory.
Professor Carlos A. Meriles focuses on the development and application of new methods in Nuclear Magnetic Resonance spectroscopy and imaging. Novel pulse sequences are used to control the nuclear spin dynamics so as to overcome basic limitations due, for instance, to undesired inter-spin interactions or magnetic field inhomogeneities. On the other hand, alternative detection schemes are developed for situations in which a standard approach is either inadequate or simply impossible. Applications are varied but his main interests center on nano-materials and biological systems.
Presently, he is working to establish a research program on micro-scale NMR and MRI. Here the main challenge comes from the fact that the standard NMR signal is too weak to probe tiny samples. For this reason, he is developing sensitive optical methods that provide information on the state of the local magnetization. Both micro-imaging and micro-spectroscopy may be carried out this way in the future. Optical pumping is also being used as a tool to reach states of nuclear hyperpolarization.
Professor Myriam P. Sarachik studies transport and magnetic properties of a variety of materials, mostly at low temperatures.
Sarachik has been studying metal-insulator transitions in three- and two-dimensional systems. Work in three-dimensional doped semiconductors, such as Si:B and Si:P, has focused on the critical behavior, critical exponents, the effect of various symmetry-breaking fields (magnetic field, spin-orbit scattering. etc.), hopping conductivity, and other issues. Recent experiments have focused on the novel and unexpected behavior of two-dimensional silicon inversion layers. The resistivity of these 2D materials exhibits metallic temperature dependence above a density, n_c, implying there is an unexpected metallic phase and a metal-insulator transition in two dimensions. Studies are underway of the anomalous dramatic response to a magnetic field applied parallel to the two-dimensional plane of the electrons. This area continues to be one of very high current interest and activity; the physical origin of the unusual behavior remains unresolved.
Work in a second area, quite distinct from the first, is on the magnetic properties of molecular nanomagnets, sometimes referred to as single-molecule magnets. These are organic crystals that contain large-spin (on the order of S=10) molecules regularly arranged on a lattice. The interest in these materials is both basic (their spins are intermediate between the classical and quantum mechanical regime) and applied (they may be useful for high-density data storage, or as qubits for quantum computers).
Professor Frederick W. Smith concentrates his experimental condensed-matter research in two main areas:
Professor Jiufeng J. Tu employs optical spectroscopic techniques to study correlated-electron systems and nano-systems. The main experimental tools used are Fourier transform infrared spectroscopy and Raman spectroscopy. Efforts are underway to couple these spectroscopic methods with magnetic measurements in collaboration with Professor Sarachik's group. Professor Tu also participates in the experimental condensed-matter research program at Brookhaven National Laboratory. For more information, visit the CCNY Optical Spectroscopy Group Home Page. Currently, there are two major areas of research:
Professor Sergey A. Vitkalov is conducting experimental research of physical properties of electron systems of reduced dimensionality. These systems demonstrate a variety of interesting physical phenomena such as Quantum Hall Effect, Coulomb blockade, weak localization. The low dimensional systems are of paramount importance for future applications in micro- and nano-electronics, utilizing quantum properties of condensed matter. Using microwave radiation, professor S. Vitkalov investigates dynamics of the electron systems at low temperatures, concentrating on fundamental properties such as the quantum electron coherence. Another project is focused on the dynamical (linear and non-linear) response of strongly correlated electrons on a surface of silicon crystals. This system demonstrates spectacular effects of electron-electron interactions, inducing strong renormalization of electron parameters. Please visit this site for more information.