An active and expanding program in experimental solid-state physics and devices is being carried out by several faculty in the Department of Physics. The research program, balanced between basic and applied projects, has a strong interaction with the Theoretical Condensed Matter Physics group and has joint efforts with other departments at Stony Brook, such as Chemistry, Earth and Space Sciences, Computer Science, Electrical Engineering, and Materials Science and Engineering. The program also benefits from interactions with scientists at Brookhaven National Laboratory (BNL) and from the synchrotron radiation facilities of BNL, located less than thirty miles from Stony Brook. The materials studied by the Experimental Condensed Matter Physics and Devices Group cover a wide range that spans from fullerenes to semiconductors to low- and high-temperature superconductors.
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Postdoctoral fellow I. Wei Tao introducing a GaAs substrate in the growth chamber of a molecular beam epitaxy system to prepare a semiconductor heterostructure that later will be used in the study of the electronic properties of two-dimensional electron gases.* |
Areas of study include the electronic structure of metals and semimetals, the formation and structure of surfaces and interfaces, the physical properties of amorphous systems, the kinetics of ordering transitions, the integer and fractional quantum Hall effects and Wigner crystallization of two-dimensional electron gases, the Josephson effect in tunnel junctions and superconducting weak links, macroscopic quantum coherence effects, correlated single-electron tunneling in ultrasmall tunnel junctions and structures, and the electronic properties of semiconductor nanostructures, quantum wells and superlattices. A large program in applied solid-state physics includes research on ultrafast superconducting digital devices and integrated circuits based on magnetic flux quantization, single-electronic devices using ultrasmall (down to 30nm) tunnel junctions, nanoscale field-effect transistors and semiconductor photonic devices.
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Vladimir Golovanov, a graduate student in Prof. Laszlo Mihaly's group, filling liquid nitrogen into the detector dewar of an infrared spectrometer. * |
The experiments at Stony Brook make use of a wide range of techniques, among others: X-ray diffraction, optical (infra-red and visible) spectroscopy, superconductor quantum interferometry, scanning electron microscopy and spectroscopy, and very-low temperature (down to 5 mK) magneto-transport (up to 17 tesla). Several projects involving synchrotron radiation are under way at the National Synchrotron Light Source at BNL. In-house sample fabrication is carried out using techniques such as molecular beam epitaxy, thin-film deposition by resistive and electron-gun evaporation and magnetron sputtering, and wet and dry etching. Optical and electron-beam lithography tools are routinely used to pattern thin-film heterostructures.
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Postdoctoral fellow Carlos Pecharromán and graduate student Joong-Kon Son setting up a low temperature experiment in Prof. Emilio Mendez's laboratory to measure the optical properties of semiconductor microcavities.* |
The Josephson effect in superconductors is the basis for a variety of current projects on superconducting devices, for instance, submillimeter wave radiation sources and mixers, and a new class of digital electronics (called Rapid Single Flux Quantum Logic) which can operate at frequencies of over 100 GHz, that is, more than 100 times faster than present semiconductor logic circuits (RSFQ WWW page). The Josephson effect is also used for the study of several fundamental physics problems such as the quantum mechanics of macroscopic variables.
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Graduate student Wenxing Zhang working with the electron beam lithography system in Prof. Lukens' laboratory to fabricate submillimeter wave oscillators based on the Josephson effect. The system can pattern devices with dimensions of less than 30 nm.* |
Related research on ultra-small tunnel junctions (having capacitances of less than a femto Farad) of both superconductors and normal metals aims at developing a novel class of devices in which information is carried by tunneling of a single electron (SET WWW page). Recent experiments have shown the trapping of a single electron in a special single-electron-tunneling device for a period of over 12 hours.
Another project has the goal of developing a useful and reproducible thin-film Josephson junction made of high-temperature superconductors (HTS). This project combines the physics of Josephson tunneling in HTS, materials aspects, and cutting edge electron beam lithography on a scale of less than 10 nm. Stony Brook researchers have recently demonstrated an all-HTS RSFQ circuit operating at temperatures of up to 30K.
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Prof. James Lukens and graduate student Richard Rouse examining the niobium trilayer deposition system, which is a central tool in the laboratory for the fabrication of multilevel superconducting circuits and devices.* |
Several basic projects deal with the nature of HTS, frequently in collaboration with the Theoretical Condensed Matter Physics group. Activities include materials preparation, tunneling measurements in various junction geometries, infrared spectroscopy on films and crystals, electrical and heat transport measurements, SQUID studies, etc.
In semiconductors, low-dimensional systems of interacting electrons exhibit new many-body ground states such as the fractional quantum Hall liquid and the quantum electron solid (Wigner crystal). Some of these states exist only in very strong magnetic fields and are of fundamental theoretical interest. Stony Brook scientists study various properties of those electronic states and their phase transitions in systems of reduced dimensionality, from two to zero dimensions.
Semiconductor heterostructures based on III-V compounds (e.g., InAs-GaSb and GaAs-GaAlAs) are also used at Stony Brook to study basic quantum-mechanical properties of solids and to explore novel device concepts. Current projects include the search for exciton formation in spatially separated two-dimensional electron-hole systems (as a possible precursor of Bose condensation), the investigation of new phenomena in hybrid semiconductor-superconductor structures, and the study of cavity quantum electrodynamics by means of semiconductor multilayers.
The structure and electronic properties of various exotic materials such as alkali metal fullerides, are studied extensively at Stony Brook. The high-resolution powder beamline at the National Synchotron Light Source (NSLS) at Brookhaven makes it possible to determine the structure of new materials. A whole class of interesting compounds, the polymeric fullerene conductors, has been discovered using this instrument. Experiments at Stony Brook include X-ray scattering, dc electrical resistivity, Hall effect, thermopower, magnetic susceptibility and optical conductivity.
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Graduate students Christine Kuntschen and Goetz Bendele using a glove box to prepare samples of RbC60, a material that spontaneously ignites upon exposure to air.* |
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