CONDENSED MATTER PHYSICS
[ Condensed Matter Experiment ] [ Condensed Matter Theory ]
CONDENSED MATTER EXPERIMENT
The general area of experimental condensed matter physics focuses on understanding the ensemble properties of matter from small clusters of atoms and molecules to macroscopic solids and liquids in their myriad forms. This includes the creation and study of new materials and their physical, electrical, magnetic, optical, and thermal properties. The experiments must often push the limits of spatial, temporal, and energy resolution, sometimes resulting in the development of new methods. As a natural consequence of this research, new technologies can emerge.
Although the experimental condensed matter physics faculty at UF have independent research programs spanning the breadth of the field, they also collaborate widely. This "team effort" approach not only accelerates progress, but also allows researchers and students at all levels to participate and gain access to a broader array of techniques and resources. Beyond the localized efforts that cross research groups (include those with our colleagues specializing in theoretical condensed matter physics) interdisciplinary collaborations exist with groups working in chemistry, materials science, medicine, and molecular biology. There are also collaborations involving visits of varying duration at numerous national and international universities and research institutions, including the National High Magnetic Field Laboratory, Oak Ridge National Laboratory, Argonne National Laboratory, Los Alamos National Laboratory, and Brookhaven National Laboratory.
A brief description of the activities of the experimental condensed matter faculty follows (for more details see the individual web pages and publications).
Nano-science: Prof. Chan exploits micro- and nano-electromechanical systems (MEMs & NEMs) for fundamental studies ranging from measurement of the Casimir force to fluctuation induced switching in systems driven far from thermal equilibrium. He also pursues more applied interests, developing new devices including a MEMs based magnetometer and novel polarization rotating devices. Prof. Hebard studies the physics of fullerenes and related materials, thin films and thin-film interfaces focusing on magnetism, and quantum effects near the metal-insulator transition in two dimensions. Prof. Rinzler fabricates and exploits nanoscale materials for device applications including transparent conductors for light emitting devices, novel transistor architectures, supercapacitors and fuel cell electrodes.
Optical Spectroscopy: Prof. Tanner studies the optical properties of solids. Materials currently under investigation include high-temperature superconductors, electroactive polymers, nano-structured metal films, and ferromagnetic oxide materials. Prof. Reitze investigates physical processes, which occur on sub-picosecond time scales and can be measured directly using ultrafast optical techniques. Examples include the interactions of charge carriers in bulk solids and low dimensional systems (quantum wells).
Novel Quantum Systems, Magnetism & Ultralow Temperature Physics: Prof. Andraka and Prof. Stewart fabricate and investigate strongly correlated electron systems with novel ground states, such as heavy fermions, non-Fermi liquids, unconventional superconductors, and quantum magnets. Thermodynamic, transport, and magnetic properties are investigated in a wide range of temperatures from 20 mK to 300 K, and in extreme magnetic fields to 45 Tesla. Prof. Biswas synthesizes materials exhibiting colossal magnetoresistance, multiferroics, and high temperature superconductors, studying their properties using transport measurements and scanning probe microscopy. Prof. Ihas studies quantum turbulence in the superfluid phase of liquid 4He to understand the mechanism of dissipation in a frictionless system and develops accurate, fast, low temperature thermometry. Prof. Lee studies low temperature properties of various materials including quantum fluids (e.g. 3He) and solids (e.g. unconventional superconductors) using ultrasound spectroscopy and NMR techniques. Prof. Meisel explores the electromagnetic properties of low dimensional molecular magnetic systems and the photoinduced magnetic response of thin films and nanoparticles of Prussian blue analogs and related molecule-based magnetic materials. Prof. Saab develops new detectors for astrophysical uses based on superconducting transition edge bolometers. Prof. Sullivan explores the fundamental properties of quantum solids and the dynamics of disordered systems over a wide range of temperatures and magnetic fields. In addition, NMR studies of materials at high magnetic fields are performed. Prof. Takano studies quantum magnetism in high magnetic fields at low temperatures, focusing on novel phenomena arising from the interplay between quantum fluctuations and geometric frustration.
CONDENSED MATTER THEORY
Strongly Correlated Electrons (Hirschfeld, Ingersent, Maslov)
Understanding the behavior of strongly correlated electron systems (materials like heavy fermion metals, ruthenates, vanadates, manganites, high-Tc cuprates and other oxides) is one of the most important problems in condensed matter physics - one that is driving a revolution in condensed matter physics, because of the apparent breakdown of the Landau Fermi liquid paradigm which has guided the field for more than fifty years. These materials have electronic degrees of freedom which interact strongly to produce exotic properties. For example, in materials with poor screening properties, such as the doped transition metal oxides, the interaction energy between valence electrons can overwhelm their kinetic energy, causing a strongly-coupled, many-body ground state of various types. As a result of this strong electron correlation, these materials display a range of useful behaviors, including high-temperature superconductivity, colossal magnetoresistance, and an extreme sensitivity to external perturbations. The group studies models of correlated systems like the Hubbard model, to understand the origins of instabilities to various phases in low dimensions, in particular the breakdown of Fermi liquid theory. There is a special interest in models of quantum impurities arising from
localized, interacting spins in metals. In some cases, "non-Fermi-liquid behavior" can be produced by such
impurities in bulk metals, on metallic surfaces, and in artificial nanostructures such as quantum dots (see Figure).
Non-Fermi liquids exhibit anomalous physical properties arising from complex interplay between various effects:
local interaction of each magnetic moment with its immediate environment, long-range interactions between moments
mediated by conduction electrons, and the consequences of lattice order/disorder.
Image: Kondo effect in quantum dot
Superconductivity (Dorsey, Hirschfeld, Kumar, Maslov)
Superconductivity, superfluidity and supersolidity are the most spectacular manifestations of quantum mechanics in the macroscopic world. High temperature superconductivity has been one of the holy grails of condensed matter physics, due in part to the array of technological applications, from lossless power transmission to levitated trains, if the mystery of how to raise the critical temperature of a superconductor can be solved. The fundamental properties of the novel classes of superconducting materials – cuprates, borocarbides, heavy fermion, organic materials, and the newly discovered ferropnictides – are also unexpected and fascinating. The group studies phenomenological aspects of macroscopic order as well as the microscopic origins of these novel quantums states, and works closely with the experimental group at UF.
Electronic Disorder (Hirschfeld, Muttalib, Maslov)
Solid state physics is based on the quantum mechanics of periodic systems, and a major frontier has always been the effect of disorder on electronic wavefunctions. One area of focus is the development of theoretical tools to explore various novel phenomena associated with a broad distribution in electronic transport properties in strongly disordered systems. A second area involves studying novel random matrix models to understand various universal properties of fluctuations of eigenvalues that correspond to an astonishingly wide variety of physical systems including heavy nuclei, chaotic and disordered quantum systems, systems near phase transitions as well as complex phenomena like earthquakes and financial markets. A third important focus is on understanding the interaction of disorder and magnetism in interacting electron systems such as high-Tc cuprates and disordere low-dimensional systems.
Image: Theoretical gapmap in inhomogeneous d-wave
Nanoscale Phenomena (Hershfield, Hirschfeld, Maslov, Muttalib) Nanotechnology is the result of the continuing trend toward device miniaturization and the characterization, manipulation, and control of function at nanometer length scales. Many nanoscale materials possess novel properties unattainable in bulk. In particular, classical ideas of electrical conduction break down completely and need to be replaced by quantum concepts. These problems are probed by the increasingly sophisticated characterization and fabrication tools such as the scanning tunneling microscope and the transmission electron microscope, which allow the resolution and manipulation of single atoms and molecules.
Magnetism (Hershfield, Kumar)
One active area of research is the class of materials known as multiferroics, materials with multiple ground states, e.g. simultaneously a ferromagnet and a ferroelectric. Technologically, these materials are promising candidates for a multi/co-functional materials. Mathematically, they pose a challenging problem with subtle consequences. There is also strong interest in the transport properties of magnetic multilayers and other devices, towards the understanding of ways in which to control electric transport via coupling to the electron’s spin degree of freedom. A final active area is in the area of magnetic phase transitions. There has been a long standing (nearly 70 years) conflict in statistical mechanics between the Ehrenfest scheme of defining the order of a phase transition and the formalism based on Landau's theory, resolved recently with the classification and understanding of third- and higher order transitions.
Ultrafast Phenomena (Stanton)
An electron in a typical metal travels one nanometer in a femtosecond. Laser pulses of this duration can therefore probe nanoscale physics. There is a major effort in the group to understand the physical phenomena in semiconductors and superconductors at these timescales. This research leads to fundamental science as well as applications in new kinds of opto-electronic devices and even magnetic devices using new magnetic semiconductors.
Image: The snapshot of a self entangled long polymer chain. Color code shows
amplitudes of thermal fluctuations of different parts of a chain.
Statistical Physics (Dorsey, Dufty, Obukhov)
Methods of classical and quantum statistical physics are applied to study the structure and dynamics of a diverse set of physical systems and states. Complex systems of polymers, rigid rods, or DNA molecules are studied to understand the types of geometric phases observed in everyday materials which do not fall into the familiar classification scheme of simple atomic systems. Sometimes the reverse is true, it appears, that in a polymer melt there are interactions similar to well known Casimir effect, in a vacuum, but with different sign. The transport and radiative properties of ions in strongly coupled plasmas are considered as diagnostic tools for high energy density matter. Dynamical systems with dissipation are being used to model the flow of granular media (e.g. sand, beans) in terms of kinetic theory and hydrodynamics.
Nanoscale Soft Condensed Matter (Obukhov)
Polymers on nanoscale can be thought as Lego™ units, which can form enormous variety of different structures and phases, whose properties are controlled by interplay of room temperature scale interactions and entropy. Another active area of research is the study of transitional and transport effects in these systems. This includes collapse and swelling of individual polymer chains and their collective motion. For example, the regular hydrodynamic description is not working on a scale comparable to the size of individual polymer chain – new approach is needed.