CONDENSED MATTER PHYSICS


[ Condensed Matter Experiment ]    [ Condensed Matter Theory ]


ABOUT CONDENSED MATTER PHYSICS
The general area of 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 and certain aspects of biological physics. The creation and study of new materials is a central goal of this field. To study the physical, electrical, magnetic, optical, and thermal properties, condensed matter experiments must often push the limits of spatial, temporal, and energy resolution. Strong collaboration among experimentalists and theorists is a necessary aspect of condensed matter research and new experimental and theoretical techniques have been developed to study and explain the properties of materials. New technologies can also emerge as a natural consequence of such studies and is a major driving force behind condensed matter research.

Although experimental and theoretical 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. Such efforts are facilitated by the Center for Condensed Matter Sciences (CCMS). Beyond the localized efforts that cross research groups, strong interdisciplinary collaborations exist with groups working in chemistry, materials science, medicine, and molecular biology with support from University-wide facilities such as the Major Analytical Instrumentation Center (MAIC) and the Nanoscale Research Facility (NRF). 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 condensed matter faculty follows (for more details follow the links and click on the figures below).





CONDENSED MATTER EXPERIMENT

A 12 X 1 pixel of a carbon nanotube enabled vertical organic light emitting transistor (CN-VOLET). A 0.2 micrometer wide wire of a phase separated managnite.
Nano-science (Hebard, Rinzler, Biswas):   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.  Prof. Biswas’s research group studies the properties of ferromagnetic and ferroelectric oxide thin films and the effect of reduced dimensions on the thin film properties.

Optical Spectroscopy (Tanner):   Prof. Tanner studies the optical effects in solids which occur in the wavelength range from the far infrared through the near ultraviolet. His group has achieved coverage over this very broad spectral range (more than a factor of 10,000) and can measure small, often anisotropic, samples, with analysis to estimate the optical conductivity and dielectric function. Materials being studied include superconductors, multiferroics, and electroactive polymers. The figure on the left shows a typical set up for such measurements.
A pnictide superconductor single crystal. An epitaxial thin film of a perovskite oxide.

Strongly Correlated Electrons and Superconductivity (Andraka, Stewart, Biswas): Dr. Andraka and Prof. Stewart grow single crystals and investigate strongly correlated electron systems with novel ground states, such as heavy fermions, non-Fermi liquids, unconventional superconductors, pnictide 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, multiferroism, and high temperature superconductivity and studies their properties using transport measurements and scanning probe microscopy.


MEMS devices used to study unconventional fluids. Effect of light on the susceptibility of Prussian blue analogs.
Novel Quantum Systems, Magnetism & Ultralow Temperature Physics (Ihas, Lee, Meisel, Saab, Sullivan, Takano):  
A cryostat at the microkelvin lab.
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. He is currently studying quasi-two dimensional superfluid 3He films using Micro-Electro-Mechanical System (MEMS) devices to understand the effect of surface disorder on unconventional superfluids. 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.

Biological Physics (Hagen, Meisel, Petkova):  Prof. Hagen’s group studies the dynamics of biological systems. Areas of interest include protein conformational dynamics and folding, which they have studied using time-resolved laser fluorescence and absorption spectroscopy. More recently the group has focused on the dynamics of gene regulatory networks. The Hagen group is particularly interested in the dynamics of bacterial quorum sensing, a phenomenon whereby bacteria communicate with each other through the exchange of chemical signals. The lab is using microfluidic devices to control and manipulate bacterial chemical and physical environments and probe the bacterial response at the single-cell level. Prof. Meisel, along with collaborators in the Department of Horticultural Sciences, is studying the effect of strong magnetic fields, up to 30 Tesla, on in vivo gene regulation in Arabidopsis thaliana. Extensions to in vitro transcription experiments are made using T7 RNA polymerase. Ancillary activities lead to new directions, and one example is the modeling of the electromagnetic fields arising from stimulating needles. Prof. Petkova is studying the fundamental biophysical process of protein folding that leads to the formation of insoluble protein and peptide aggregates. A detailed biological physics website can be found here.

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.  


Kondo effect in a quantum dot.
Superconductivity   (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.
Theoretical gap map of an inhomogeneous d-wave superconductor.


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.  


A snapshot of a self-entangled long polymer chain. Color code shows amplitudes of thermal fluctuations in different parts of the chain.
Statistical Physics   (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.

Soft Condensed Matter   (Obukhov)  
Much of modern condensed matter physics focuses on the nature of condensed phases, as characterized by symmetries, generalized elasticity, topological defects, and conservation laws. These concepts are especially important in understanding “soft matter,” partially ordered phases of matter, such as liquid crystals, with anomalous elasticity or fluctuation effects. 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. Obukhov’s 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.