Kieran Mullen
Assistant Professor
B.S. 1982 Georgetown
Ph.D. 1989 Michigan
I am interested in the physics of novel effects in quantum systems. My work to date falls into two broad categories: mesoscopic electronic devices, and quantum Hall systems.
"Mesoscopic" systems are those in between the regimes of classical and quantum physics, typically less than a micron across. Experimentalists can routinely fashion devices so small that the electrostatic energy of a single electron can control the flow of current, or in which electrons can travel coherently from one side of the device to the other. The theoretical challenges are to understand how the quantum mechanical effects in the microscopic device couple to macroscopic world of voltmeters and ammeters, and how to take advantage of the novel dynamics for new applications.
In particular I have worked on how to design a refrigerator with an electron gas as its working fluid, how small rings can serve as synthetic atoms in periodic arrays, and how the inclusion of nanotubes affects heat transport in mixtures.
In the quantum Hall regime we freeze out the kinetic energy of the electrons applying a large magnetic field. This allows interactions to come to the fore. We have looked at large, many electron excitations called "skyrmions" and "merons." These exotic creatures are twists in the texture of the local electonic spins. Like the twist that can sometimes appear in your phone cord, these twists can only be removed by large scale motions of the system.
K. Mullen, H. T. C. Stoof, M. Wallin, and S. M. Girvin, "Hexactically Ordered Superfluids", Physical Review Letters 72, 4013 (1994).
K. Mullen, D. Loss, and H. T. C. Stoof, "Resonant Phenomena in Compact and Extended Systems", Physical Review B 47, 2689 (1993).
J. P. Carini, J. T. Londergan, K. Mullen, and D. P. Murdock, "Multiple Bound States in Sharply Bent Waveguides", Physical Review B 48, 4503 (1993).
D. Loss and K. Mullen, "Dephasing by a Dynamic Environment", Physical Review B 43, 13252 (1991).
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