Brookhaven Condensed Matter Physics

Condensed matter physicists study the properties of bulk matter—solids and liquids—as well as the properties exhibited at surfaces and interfaces, with a view to obtaining a fundamental understanding of the unusual properties that materials can exhibit. These problems are some of the most challenging in physics today, but have the huge pay-off in that such an understanding may ultimately lead to improved materials for use in applications as diverse as computing, memory storage, electric motors, and energy storage and transport. At Brookhaven Lab, this work includes both experimental and theoretical studies.

Much of the experimental work carried out today uses the National Synchrotron Light Source (NSLS, shown at right)—one of the premiere synchrotron light sources of the last two decades. Commissioned in the 1980s, the NSLS is host to more than 2,200 users per year and produces copious amounts of light, from the infrared to the ultraviolet to the x-ray. By using this light as a probe, scientists can learn about the arrangement of the atoms and electrons in the materials and how they behave under various conditions. Among other projects, BNL scientists have played leading roles in the development and application of resonant and inelastic x-ray scattering techniques to the study of magnetic and other materials, have pioneered the use of photoemission techniques (based on the photoelectric effect that Einstein first understood 100 years ago) for looking at electronic and magnetic materials, and have carried out some of the seminal experiments to understand the atomic and magnetic structure at surfaces.

Another excellent probe of condensed matter is the neutron. A lot of early research in this area was conducted at Brookhaven’s two research reactors; first, the Brookhaven Graphite Research Reactor, in operation from 1950 to 1968, and then its successor, the High Flux Beam Reactor (1965-1999). Both reactors produced streams of neutrons for the study of materials—from crystals of large biological molecules to metal oxides—and were major centers for neutron scattering research during the time they operated. Now condensed matter physicists at Brookhaven perform neutron research at top reactors across the globe, often using crystal samples that are grown at the Lab.

One aim of Brookhaven’s condensed matter program is to explain the causes of high-temperature superconductivity in various complex materials. This has become a major focus of worldwide condensed matter research since the discovery of high-temperature superconductivity in 1987. Exciting joint theoretical and experimental work has shown that certain high-temperature superconductors, known as copper oxides, contain alternating magnetic and charge-ordered regions, called “stripes.” These stripes, which display a certain magnetic behavior called “antiferromagnetism,” were first observed at Brookhaven. In 2004, Brookhaven researchers and their collaborators found that stripes may be essential for high-temperature superconductivity.

Another theory suggests that superconductivity in copper oxides may be the result of arrangements of “holes”—empty spaces left by missing electrons. Experimental support for the theory comes from studies at the NSLS that employ spectroscopic methods. Spectroscopic techniques use x-ray, ultraviolet, or infrared “photons” (tiny particles of light) to probe the electronic properties of materials, including chemical bonds and magnetic structure. Spectroscopy is a very useful tool for research in condensed matter and Brookhaven has played a lead role in its development.

Other areas of research in this field include correlated electron behavior, low-temperature superconductivity, and non-Fermi liquid behavior in oxides and synthetic conductors. Brookhaven physicists also study magnetism and low-dimensional structures, and perform studies to determine the structures of complex materials and surfaces.

Brookhaven Lab is also responsible for designing and building the Accumulator Ring Project at the Spallation Neutron Source (SNS), an accelerator-based neutron source being built at Oak Ridge National Laboratory. In addition, Brookhaven is building one of the SNS’s major spectrometers for neutron scattering, called HYSPEC.

> Soft Condensed Matter Physics

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Last Modified: February 4, 2008