Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session P1: Buckley Prize, Bouchet Award, and Apker Award Talks |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Sidney Nagel, University of Chicago Room: LACC 152 |
Wednesday, March 23, 2005 11:15AM - 11:51AM |
P1.00001: Quantum spin dynamics and coherence in solids Invited Speaker: Even while their existence as individuals is fundamentally quantum mechanical, derivable from atomic physics, for many purposes the spins in solids behave as classical objects. In particular, virtually the entire science of solid state magnetism, including phenomena as diverse as phase transitions, domain walls, and magnons can be understood in terms of classical rotors, subject to varying anisotropic potentials determined by external as well as internal (crystal) fields, coupled to each other via dipolar and exchange interactions. Even so, there has long been theoretical suspicion that when the interactions are antiferromagnetic rather than ferromagnetic, quantum mechanics might manifest itself on scales larger than the interatomic spacings associated with crystal fields and exchange interactions. Recent experiments on antiferromagnets, where the quantum fluctuations are enhanced by coupling to mobile electrons or by geometric factors such as system dimensionality, reveal this suspicion to be justified. Some of the materials, including even the simple two- dimensional Heisenberg antiferromagnet, display anomalous spin wave amplitudes and dispersion, while for others, classical order itself is replaced by mesoscopic quantum ‘order’ or coherence. Apart from their intrinsic interest as magnets with strong quantum fluctuations, systems of this type are also of more general importance as they include both the heavy fermion metals and high temperature superconductors, many of whose interesting properties are thought to be derived from the same fluctuations. Work is currently supported by a Wolfson Royal Society Fellowship and the Basic Technologies Progamme of the UK Research Councils. [Preview Abstract] |
Wednesday, March 23, 2005 11:51AM - 12:27PM |
P1.00002: Spintronics: Semiconductors, Molecules, and Quantum Information Processing Invited Speaker: There is a growing interest in exploiting electronic and nuclear spins in semiconductor nanostructures for the manipulation and storage of information in emergent technologies based upon spintronics and quantum logic. Such schemes offer qualitatively new scientific and technological opportunities by combining elements of standard electronics with spin-dependent interactions between electrons, nuclei, electric and magnetic fields. Here we provide an overview of recent developments in the field through a discussion of temporally- and spatially-resolved magneto-optical measurements, initially designed for probing local moment dynamics in magnetically doped semiconductor nanostructures. We demonstrate new electrical schemes for the local generation and manipulation of spins in conventional semiconductor heterostructures, thereby providing a compelling proof-of-concept that quantum spin information can be controlled within high-speed electrical circuits. Furthermore, we discuss a different experimental approach that enables the molecular wiring and assembly of colloidal semiconductor nanostructures to engineer hybrid systems for room temperature coherent spin transport. These experiments explore electronic, photonic, and magnetic control of spin in a variety of nanostructures, and show significant steps towards spin-based quantum information processing in the solid state. [Preview Abstract] |
Wednesday, March 23, 2005 12:27PM - 1:03PM |
P1.00003: Quantum Tunneling of the Magnetization in Molecular Nanomagnets Invited Speaker: Molecular nanomagnets, sometimes referred to as single molecule magnets, have attracted a great deal of recent attention for interesting behavior that is borderline between the classical and quantum mechanical regimes, and because of their potential usefulness for high-density data storage and quantum computation. Quantum mechanical processes are observed in these materials on a macroscopic scale in the form of steps in the magnetization curves.* Two particularly simple prototypes, Mn$_{12}$-acetate and Fe$_{8}$, have been studied in great detail. Typical behavior of the class will be examined by considering Mn$_{12}$-acetate: the structure of the molecule, the tetragonal (four-fold symmetric) crystal, the Hamiltonian that models the behavior, and the tunneling process that gives rise to the magnetization steps. * J. R. Friedman, M. P. Sarachik, J. Tejada, and R. Ziolo, Phys. Rev. Letters, \textbf{76}, 3830 (1996). [Preview Abstract] |
Wednesday, March 23, 2005 1:03PM - 1:39PM |
P1.00004: Single-Electron Transport and Device Applications Invited Speaker: In recent years, there has been a considerable amount of theoretical and experimental activity involving surface acoustic waves (SAWs). Interest in this field has centered around the evidence for single -electron transport in piezoelectric materials such as GaAs/AlGaAs heterostructures and its potential use as a current standard. Several device applications involving SAWs for transporting electrons (and holes) include quantum computing, where the spin is the qubit that is moved across a network of quantum gates by SAWs, and a single-photon source through the recombination of electrons and holes. The SAW quantum computer is a “dynamic” qubit type where the quantum information actually travels during the computation. This type of qubit has the advantage of delivering information quickly through the circuit when decoherence times are short. We consider specific architectures that will allow quantum entaglement and electron-hole recombination. We also propose a novel scheme of photon detection which uses SAWs for transporting photo-generated electrons and holes. Potential applications of the concept include imaging arrays in the visible and infrared regions and single photon detection. A preliminary feasibility study has indicated that the acoustoelectric photon detectors/imaging arrays can feature an extremely low dark current rate. The concept has advantages over Charge Coupled Devices (CCDs) because of its simplicity, speed of operation and high sensitivity (down to the single photon level). The device uses SAWs to transport charge along wave guides. We explore the application of the detector to the improvement of security. [Preview Abstract] |
Wednesday, March 23, 2005 1:39PM - 2:15PM |
P1.00005: Asymmetry in RNA Pseudoknots Invited Speaker: Single-stranded RNA can fold into a topological structure called a pseudoknot, composed of non-nested double-stranded stems and single-stranded loops. Our examination of the {\tt PseudoBase} database of pseudoknotted RNA structures reveals asymmetries in the stem and loop lengths and provocative composition differences between the loops. By taking into account the difference between the major and minor grooves of the RNA double helix, we explain much of the asymmetry with a simple polymer physics model. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700