Rutgers University Department of Physics and Astronomy

200-01 Handbook for Physics and Astronomy Graduate Students

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Research Programs

Experimental Condensed Matter Physics

Experimental research on condensed matter physics at Rutgers has a long and distinguished history. The university's physics laboratory is named after Bernard Serin, who in 1950 discovered the isotope effect in low-Tc superconductors. This tradition in studies of superconductivity continues as exciting experiments and theoretical work on high Tc superconductors are carried out. Other vigorous areas of research include such phenomena as metal-insulator transition, two-dimensional electron systems, magnetism, and quantum fluids and solids. Extensive collaborations exist with the Department of Mechanics and Materials Science and the Department of Chemistry at Rutgers, the Cornell synchrotron radiation facility, and Brookhaven National Laboratory.

Laboratory for Surface Modification

The Laboratory for Surface Modification is an interdisciplinary laboratory with state-of-the art equipment, involving approximately twenty faculty members from different departments. The facility is located in Serin Physics Laboratory and is directed by Professor Theodore E. Madey. Surface science involves research in the overlapping disciplines of chemistry, physics, materials science, and engineering. Research in all these fields is necessary to advance scientific knowledge of the phenomena that occur at the atomic level at a surface or an interface. Aside from the considerable conceptual interest in this area, progress in this field is having an impact on such diverse subjects as telecommunications, petrochemistry, computer science, and minerals and chemicals.

Professor Eva Andrei

Our research program focuses on the diverse phases of matter and associated dynamic and thermodynamic properties arising from the competition between particle-particle interactions and fluctuations. The former are inherent to the particles while the latter are external, stemming from a random potential, temperature or quantum effects. By varying the relative strength of these ingredients new phases and physical properties can be engineered. We use two model systems which are exceptionally versatile and easy to manipulate under standard laboratory conditions: a) magnetic vortices in type II superconductors and b) two-dimensional (2D) electron systems. a) Vortices. This work is currently centered on the dynamics of moving vortex phases and order-disorder transitions. We have developed novel transport techniques including swept radio frequency spectroscopy, current pulsing and ultra-fast current ramps which have enabled us to follow the vortex state as its motion unfolds in response to an applied current. Our experiments lead to the discovery of a new vortex state which exhibits a number of striking properties including frequency memory and unusual training effects. b) 2D electron systems. 2D electron layers are created by depositing electrons on the surface of a weakly polarizable substrate such as liquid helium or by trapping them at a semiconductor junction. The in-plane physics is governed by competing energy scales which give rise to a variety of phases such as electron crystal, dipole crystal, glass, a quantum liquid, quantum Hall states, etc. We use broad band radio frequency spectroscopy and transport measurements to study the dynamics, thermodynamics and the mechanisms driving the various phase transitions.

Professor Robert Bartynski

Our group is engaged in experimental studies of the electronic properties of surfaces and interfaces. The research focuses primarily on three areas: The influence that quantum size effects in ultrathin metal films have on their interaction with adsorbed atoms and molecules; the growth and morphology of metal overlayers on ferroelectric oxides; and the electronic properties of solids and their surfaces as probed by Auger-photoelectron coincidence spectroscopy. Our research employs a number of electron based spectroscopies, including angle resolved inverse and direct photoemission, both in-house and at synchrotron radiation facilities, as well as scanning tunneling microscopy and spectroscopy.

Professor Sang-W. Cheong

New physics on new materials, particularly correlated materials. The primary focus has been the experimental study of the charge and spin states in correlated electron systems including high Tc superconductors and colossal magnetoresistance (CMR) compounds. The recent success includes the understanding of the quantum magnetism in 2D S=1/2 antiferromagnets, the discovery of the charge/spin stripe states, and the understanding of the strong coupling of spin, charge and the lattice in the CMR manganites. This type of exploration requires wide-range interdisciplinary researches and extensive collaboration, allowing students accustomed to various fields such as condensed matter physics, chemistry, and materials science and also helping students to develop a scientific network. Our research employs magneto-transport and thermodynamic measurements, neutron and x-ray elastic/inelastic scattering experiments, and spectroscopic experiments such as optics and photoemission experiments as well as new phase synthesis and crystal growth.

Professor Mark Croft

The current central thrust of Prof. Croft's research involves the use of synchrotron radiation x-ray spectroscopy measurements to probe the structure and electronic states of new, novel, and technologically important materials. Both x-ray absorption spectroscopy and x-ray diffraction experiments are carried out in runs at the Brookhaven National Synchrotron Light Source. A wide range of materials and solid state problems are encompassed in this effort, a representative selection of examples of which are noted. One area of concentration addresses the electronic structure of High Tc related compounds that underlies the collapse of magnetism, the insulator- metal transition, and the superconductivity that occur in these materials. [Both bulk and pulsed laser deposited thin films are used in this work.] Another area of effort deals with the transition metal d-orbital role in the electronic structure of compounds. Recent work has also involved the question of face versus body centered cubic structure in metallic/magnetic multilayered materials. Prof. Croft also has an on going involvement in mixed valent, heavy Fermion problem. In these studies the evolution from local-magnetic- moment to delocalized-band electronic behavior is studied by low temperature magnetic, transport, and thermal measurements in conjunction with spectroscopic measurements. All of the work in this program emphasize broadly based materials synthesis techniques.

Professor Eric Garfunkel (Chemistry)

The broad goal of our research program is to learn how to design surfaces, interfaces and thin films for microelectronics and other advanced materials applications. We employ electron spectroscopy, ion scattering, scanning probe microscopy, vibrational spectroscopy, and other surface science and thin film methods. Recent work has included studies of oxidation, molecular and metal adsorption and reaction, and thin film growth. One major project involves studies of ultrathin dielectrics (silicon oxynitrides and metaloxides) for nanoelectronic devices. We examine problems of composition, reaction mechanism, structure and electrical properties. Other projects include structural and thermochemical aspects of metallization, studies of the polymer-metal interface, and basic studies for molecular electronics.

Professor Michael E. Gershenson

The research in my group is focused mostly on Quantum Transport and Interactions in Mesoscopic Conductors (both metallic and semiconductor structures, one- and two-dimensional with respect to the quantum effects).We specialize in ultra-low-noise measurements at millikelvin temperatures, and our research employs the state-of-the-art cryogenic equipment, modern data-acquisition methods, and a variety of the solid-state-electronics techniques for sample preparation. Current research problems involve:

effects of electron-electron interactions on electron localization and hopping conductivity in low-dimensional conductors

dephasing in low-dimensional conductors at ultra-low temperatures

electron-phonon interaction in low-dimensional conductors at ultra-low temperatures

hopping conductivity in low-dimensional conductors with a large localization length

metal-insulator transition in two dimensions.

We collaborate with the Jet Propulsion Lab on development of Ultra-Sensitive Hot-Electron Direct Detectors for the submillimeter and far infra-red electromagnetic radiation.

Professor Torgny Gustafsson

My research is in the field of surface physics, in particular the study of the geometric structure of metal surfaces. Many surfaces have a geometric arrangement that is different from that of the bulk and it is important to understand and eventually influence the forces that cause these effects. Using the scattering of very energetic ions and equipment unique to Rutgers, we can determine the surface geometry with very high accuracy. Recently, we have modified the structure of these surfaces through the adsorption of adatoms, creating new superstructures with interesting, unexpected and possibly useful properties.

Professor Jane Hinch (Chemistry)

We are investigating atomic and molecular beam scattering from surfaces prepared under ultrahigh vacuum conditions. We investigate the nature of the molecular surface interactions and quantify processes such as phonon creation/annihilation, electron-hole pair excitation, electron transfer or trapping, and adsorption. The major focus of our research efforts involves thermal-energy atomic helium scattering as a technique in the study of clean and adsorbate covered surfaces. Helium is an extremely inert, surface-sensitive, diffractive probe of surface topographies and long range ordering phenomena. We investigate also the dynamics of surfaces and low energy excitations and surface diffusion processes. Each of these features are of utmost importance in thin film growth at surfaces. In addition we use both diffraction and real-space scanning tunneling microscopy in in-situ studies of the growth of thin films by both thermal evaporation and chemical vapor deposition.

Professor Valery Kiryukhin

My research is in the field of experimental condensed matter physics. In particular, I am interested in strongly correlated materials (such as colossal magnetoresistance materials and high Tc superconductors), and in low-dimensional quantum magnets (e.g. quantum spin-chains and two-dimensional systems such as those found in high Tc cuprate superconductors). In the latter case, effects of impurities are of particular interest. The main experimental technique that we use is x-ray and neutron scattering. In many cases, our measurements are conducted at low temperatures and in high magnetic fields. The experiments will be performed at the nearby research facilities (Brookhaven Lab, NIST),and using in-house x-ray, magnetic measurement, and crystal growth equipment.

Professor Haruo Kojima

Superfluid He-3, which occurs below 2.6 mK, has a rich variety of phenomena whose analogs can be found in superfluid He-4,nematic liquid crystals, antiferromagnets, and ferromagnets. We have been carrying out a number of experiments to measure magnetic, thermodynamic, and hydrodynamic properties of superfluidHe-3. Our most recent research has been with the superfluid He-3 A-1 phase in magnetic fields as high as 15 teals. A special nuclear demagnetization apparatus has been built to cool liquid He-3 down to 1.5 mK in such high magnetic fields. A unique hybrid form of second sound, called spin-entropy wave exists in A-1 phase. The velocity and attenuation of the spin-entropy are being measured to extract the superfluid fraction, the spin diffusivity, and the thermal conductivity. Under suitable conditions, the spin-entropy wave can be used to study liquid crystal-like anisotropy effects. Textural transitions induced by superfluid flows are being studied using the spin-entropy wave. Preliminary work on sonoluminescence in water is being carried out. Measurements spin-lattice relaxation time and susceptibility of a non-Fermi liquid system,CeCu_6-xAux are also being carried out using NQR and SQUID techniques.

Professor Peter Lindenfeld

Our work is primarily on the high-temperature superconducting systems, not only when they are actually in their superconducting state, but also in the neighboring metallic and magnetic insulating states. These "normal" states are, in fact, quite anomalous, and may well contain essential clues to understanding of the superconducting behavior. We study the region in the vicinity of the various phase transformations that occur when a magnetic field is applied, or with changes in composition that alter the concentration of charge carriers, the amount of disorder, or that introduce magnetic moments.

Professor Theodore E. Madey

My research is in experimental surface physics. Particular emphasis is on the use of ultrahigh vacuum methods to characterize the physics and chemistry of processes that adsorption, chemisorption, the nucleation and growth of ultrathin metal films, catalysis, photoelectron emission, ion scattering, and electron/solid interactions. My present research activities are focused in three areas: (1) we are studying the relation between surface structure, electronic properties, and reactivity of bimetallic surfaces; methods are used in this program include atomic-resolution scanning tunneling microscopy, electron diffraction, and synchrotron radiation. (2) we are determining the mechanisms of electron- and photon-stimulated desorption of atoms and ions from surfaces (including charge transfer and energy transfer phenomena) using a unique apparatus that permits angle-resolved ion detection, and (3) we are probing nucleation, growth, epitaxial structure and interfacial reactivity of ultrathin metal films on oxide surfaces using electron and ion spectroscopies, coupled with high resolution (sub-nanometer) electron microscopy.

Professor Russell Walstedt

Nuclear magnetic resonance (NMR) studies of correlated electron systems. The current focus of my condensed matter NMR program is the superconducting cuprates and related oxide materials. The history of the last decade has shown this arena to be endowed with a wide variety of new physical effects. The NMR probe addresses, among other things, the static and dynamic magnetic responses of these systems, thus sharing an extensive interface with neutron scattering studies. In spite of intensive research on, e.g., the cuprate superconductors, many basic questions about the NMR dynamics (i.e., nuclear spin relaxation processes) remain unresolved. Further, the new "stripe phase" materials as well as the manganate family of "colossal magnetoresistance" compounds pose a rich panorama of fresh challenges to the NMR experimenter. Our NMR laboratory employs an 8 Tesla superconducting magnet, with computer-controlled spectroscopy and dynamics routines. With temperature capability from 4.2K up to 1000K and beyond, we are equipped to mount a broad-gauge investigation of any of the systems contemplated. Sample materials will be obtained through a long-standing collaboration with Prof. S-W. Cheong. Lastly, we note that many aspects of sample preparation and characterization are part of our research program in addition to the NMR work, giving a broad perspective of condensed matter experimental studies.

Professor Frank Zimmerman

Our research in experimental surface physics is directed at obtaining a detailed understanding of the fundamental mechanisms involved in dynamical surface processes, in particular laser-induced thermal and photochemical surface processes. We seek to understand the excitation mechanisms and the dynamics of laser-induced desorption, dissociation, and reaction of adsorbed molecules. A powerful way to gain insight into the dynamics uses quantum state resolved, laser spectroscopic detection of desorbed products to determine their final state distributions in the translational, rotational, vibrational, and electronic degrees of freedom. In addition, we intend to use ultra-short ("femtosecond") laser pulses to probe surface dynamics in real time.

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Revised November, 2000