We have studied the static and dynamic magnetic properties of Heisenberg quantum antiferromagnets (QHAF) diluted by random nonmagnetic impurities, such as La2Cu1-xMxO4 (M=3DMg, Zn), using spin-wave theory and the quantum nonlinear sigma model (QNLsM). To study the interplay of quantum fluctuations and nonmagnetic disorder on La2Cu1-xMxO4, we modeled the lamellar QHAF as a lattice with tetragonal symmetry and studied the system using spin-wave theory in the ordered phase and modified spin-wave theory in the paramagnetic phase. The Green's function method was applied to study the magnetic properties of La2Cu1-xMxO4. The nonmagnetic disorder is treated by the single-site averaged t-matrix approximation. We calculated the local  magnetic moment, the two-dimensional spin-correlation length, the nuclear relaxation rate, and the 3D Neel temperature, all of which showed good agreement with the available data of quantum MC simulations and experiments. We found that the hydrodynamic description of spin-wave breaks down at a  characteristic wave-vector kc, while the order parameter is free from anomalies. We argue that this dichotomy originates from the strong scattering of the low-energy excitations in two dimensions. We alternatively propose a two-dimensional effective-field theory (the quantum nonlinear sigma model) combined with classical percolation theory to study the enhanced effects of quantum fluctuations on the magnetic properties of La2Cu1-xMxO4 introduced by the nonmagnetic disorder. The spin stiffness and the spin-wave velocity are renormalized by nonmagnetic dilution according to classical percolation theory. Both theories show that the effect of quantum fluctuations on the suppression of magnetic ordering is enhanced by the nonmagnetic doping.

The advection of a passive scalar (e.g., dust particles or a temperature field) by a turbulent flow shows its own scaling behavior, which cannot easily be derived from that of the underlying velocity field. This talk shows that even the passive scalar advection by a noisy Burger's flow in one dimension has a nontrivial scaling behavior, which is qualitatively different in different regions of parameter space. The conclusions are based on renormalization group calculations, computer simulations, and scaling arguments.

I will first discuss generalizations of quantum mechanics in the geometric framework. Then I will briefly review the structure of Nambu classical mechanics, which represents a non-trivial generalization of the standard canonical formalism of classical mechanics. I will then propose a generalization  of the standard quantum mechanics based on the classical Nambu triple bracket and discuss its basic features and applications.

Self-assembled nanoarrays fabricated in porous alumina templates have recently attracted a great deal of attention. The nanoarrays have many potential applications, for example, in magnetic recording, computing, nanoelectronics, etc. They are also scientifically interesting because they are model systems to study fundamental phenomena at the nanoscale. In this talk, I will describe the method by which porous alumina can be prepared in the laboratory with good control over the pore size. I will discuss the many ways in which the templates can be used to prepare nanoarrays of various materials: metals, alloys, compounds, multilayers, etc. These nanoarrays can be characterized very easily using AFM, SEM and TEM techniques. One can also carry out a whole range of measurements on these systems including magnetic, optical, electrical, etc. Some of my results on magnetic, semiconducting and superconducting nanoarrays will be presented in this talk and their possible applications in devices will be discussed.

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Quantum computers potentially can be much more efficient than conventional computers for certain applications. Quantum bits or qubits, which are the basic building block of a quantum computer, have been demonstrated in different systems. And in some systems quantum computation involving a few qubits have been performed. However, most of these systems are not suitable for scaling up to provide large number of qubits required for useful computation. Solid state qubits, in particular those based on superconducting devices employing Josephson junctions, are promising candidates for large scale implementation. These devices are made with nanofabrication technology and are much easier to scale up. There have been some promising progress in developing superconducting qubits. In this talk recent results will be reviewed.

Novel oxide thin films, such as highly conductive SrRuO3 and La1-xSrxCoO3, superconductive YBa2Cu3O7-d, highly dielectric CaCu3Ti4O12, ferroelectric Ba1-xSrxTiO3 (BSTO), and ferromagnetic La1-xCaxMnO3, have been epitaxially grown for various device applications, such as field effect transistors, MEMS, tunable microwave elements, quantum cascade systems, and solid state fuel cell applications. For instance, ferroelectric (Ba,Sr)TiO3 thin films have been fabricated for tunable microwave phase shifters and exhibited excellent room temperature dielectric properties with high dielectric constant, low loss tangent, and large tunability.  Microwave property measurements indicated that the room temperature coupled microwave phase shifter has achieved a phase shift over 275o at 24 GHz and a figure of Merit of near 70o/dB (best record). Furthermore, microstructural studies suggest that the conservative and non-conservative antiphase boundaries can form in the thin films due to "surface steps and terraces induced antiphase domain formation mechanisms". Thus, "Artificial Domain Structured Optoelectronic Modulator" (ADSOM) is proposed from this epitaxial model for optoelectronic device applications such as quasi-phase modulators, quantum cascade (QC) lasers, and new optoelectronic device systems. Giant dielectric CaCu3Ti4O12 thin films (e~105) have been epitaxially grown to investigate the unusual physical properties of this newly discovered material.  Many interesting phenomena have been found from the as-grown films. In addition, pulsed laser induced self-assembly (PLISA) is a unique technique that we have developed for synthesizing nano-oxide particles and particle arrays with modulated structures.  By controlling the irradiation energy, irradiation pulse period, and film thickness, various nanoparticle patterns with artificial periodical structures have been achieved. Details will be presented in the seminar.

I will present evidence for a percolation transition to explain the relatively sharp melting transition observed in the networked DNA-gold nanoparticle system. I will also describe how coexistence of different oligomeric states affects the self-assembly of a large multisubunit human enzyme, which has led to difficulty in experimental interpretation in the past.

The experimental and theoretical tools that exist for studying two-dimensional surfaces give phenomenal insight into the physics of matter on the atomic scale. For example, with the scanning tunneling microscope (STM) the positions of each atom which make up a surface can be seen. To directly compare with this experimental technique, there exist theoretical methods for calculating the equilibrium atomic structure of a surface. Conventional wisdom would dictate that an atomically smooth single crystal surface is a lower energy structure due to the added cost in energy of producing a step edge.  Contrary to this assumption, one-atomic-layer-high islands spontaneously form (without growing any material) on the GaAs(001) surface when it is annealed around 525°C. It will be shown that these structures are in equilibrium and can be described by the celebrated 2D Ising model. STM images of the microscopic domain structure on a scale comparable to the gas's constituents give never-before-seen insight into the 2D Ising model. These domain structures are analogous to the 2D magnetic domains formed in a ferromagnet when exposed to an applied magnetic field. Correlation functions, asymmetric coupling energies and critical exponents will be presented, as well as the implications for modeling the growth of compound semiconductor devices.

Exact RG flow equations have been recently used in the framework of high energy physics, (QCD, quark confinement) and equilibrium critical phenomena (O(N) models, KT transition...) as a nonperturbative technique to treat quantum or thermal fluctuations. Surprisingly, no applications of these techniques exist yet in the study of nonequilibrium phase transitions. After reviewing the general method, based on simple ideas (hoping this part will also help students understanding the physical meaning of RG procedure, often hidden in the technical details of perturbative expansions), I will show how to derive flow equations for diffusive systems and directed percolation. I will finally present the results obtained recently for the DP universality class which I hope will motivate the audience for comments and discussion.

The effect of introducing a mass dependent diffusion rate m^-α in a model of coagulation with single particle break up is studied. The model with α = 0 is known to undergo a nonequilibrium phase transition as the mass density  in the system is varied. This transition is shown to be curbed, at finite densities, for all α > 0. The exponents characterizing the probability that a randomly chosen site has mass m in the steady state, are calculated exactly using scaling arguments. The full probability distribution is obtained by using a mean field approximation and compared with the results from numerical simulations.

By means of a 3D Monte Carlo simulation we study the current-voltage characteristics and voltage noise spectrum of driven magnetic flux lines interacting with randomly placed point and linear defects, as well as with columnar defects arranged in a square-lattice array at low temperatures. Near the depinning current J_c the voltage noise spectrum universally follows a power law. For currents J > J_c distinct peaks appear in the power spectrum which are considerably more pronounced for extended as compared to point defects, and reflect the spatial distribution of the pinning centers.