The development in the last decade of a variety of new conceptual and computational tools has led to major changes in our understanding of condensed matter systems. Recent work at Stony Brook has focused on quantum mechanical effects on a macroscopic scale, collective phenomena in low-dimensional solids such as quantum dots, the quantum Hall effect, and properties of the mesoscopic metals such as correlated tunneling and single-electron effects. Computer simulation of solids and liquids (including problems involving interfaces, surfaces, amorphous states, and electronic structure) is being performed using both local dedicated super minicomputers and remote supercomputer facilities. In statistical mechanics there is very active research into one- and two-dimensional systems where exact mathematical calculations can be made. These include studies of phase transitions, solitons, and spin diffusion. The effort spans the range from quantum field theory to computer studies.
Condensed matter physics has influenced many areas from particle theory to device technology. The theory of condensed matter is enriched by a wealth of interesting materials and experiments. Stony Brook has a strong condensed matter theory effort, with close and useful collaborations between experimentalists and theorists in single electronics, high Tc superconductivity, quantum Hall effect, critical phenomena, disordered systems and elsewhere.
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A meeting of Prof. Averin's group. The students Athanassias Bardas and Hasan Imam, Prof. Averin, and postdoc Alexander Korotkov study various theoretical problems of mesoscopic physics, including quantum dynamics of nanoscale Josephson junctions.* |
High temperature superconductors were an enormous surprise when they were discovered in 1986, and continue to puzzle condensed matter theorists. At Stony Brook, we are investigating both novel and conventional approaches to try to understand the peculiar properties found experimentally. Related to this is an effort to understand metal-insulator transitions and magnetism in other oxides of transition metals. Some of these projects involve large scale numerical modeling on supercomputers, and increasingly on parallel machines. Transport properties and anharmonic lattice dynamics are among the other problems being studied.
Two-dimensional electrons in high magnetic fields form a highly correlated liquid state of matter, which exhibits a number of dramatic phenomena, most notably the fractional quantum Hall effect. A theory has been developed at Stony Brook which shows that the fundamental order of this state is characterized by the existence of a new particle called the "composite fermion", which is the bound state of an electron and the vortices of the wave function. Various properties of the composite fermion states have been studied. Several recent experiments, including one at Stony Brook, have reported direct observation of composite fermions. Composite fermions have also been found to be relevant to "quantum dots" containing a few electrons at high magnetic fields.
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Profs. Jain and Allen. The condensed matter theory group shares a cluster of networked workstations whose uses have included numerical confirmation of Jain's "Composite Fermion" theory of the quantum Hall effect.* |
"Single-Electronics", which considers effects of charging macroscopic solid state systems by a single electron or a single Cooper pair is subject of extensive investigation by faculty in the Department. Surprisingly, single electron effects can be quite substantial and have recently been observed in several experiments. They also hold the promise of important new device applications (see the experimental section). Important theoretical issues in the field of single-electronics include effects of quantum fluctuations, macroscopic quantum tunneling, wave-particle duality, Wigner crystallization and so forth.
The Stony Brook condensed matter theory group enjoys a close working relationship with theoretical colleagues at nearby Brookhaven National Laboratory, who supervise Stony Brook students from time to time. This collaboration provides access to leading experts in the theories of high temperature superconductors, one-dimensional conductors, alloy theory, and correlation effects in metals.
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