Physics 795 Condensed Matter Theory Ralf Bundschuh Jason

Physics 795: Condensed Matter Theory Ralf Bundschuh Jason Ho C. Jayaprakash Julia Meyer Bruce Patton Bill Putikka Mohit Randeria Will Saam David Stroud Nandini Trivedi John Wilkins Physics 795: CMT - Nov 3, 2006 1

Condensed Matter Theorists @ OSU R. Bundschuh W. Putikka J. Ho M. Randeria C. Jayaprakash W. Saam & J. Wilkins J. Meyer D. Stroud B. Patton N. Trivedi Physics 795: CMT - Nov 3, 2006 2

Physics 795: CMT - Nov 3, 2006 3

Julia Meyer Mesoscopic physics [ meso = somewhere in between micro & macro ] Interactions and disorder in low-dimensional & nanostructured systems CURRENT PROJECTS: - deviations from one-dimensionality in interacting quantum wires - ultracold dipolar gases in optical lattices - proximity effect in superconductor-ferromagnet hybrid structures MY GROUP: 1 graduate student [ possibly one more opening ! ] + looking for one postdoc Physics 795: CMT - Nov 3, 2006 4

Bill Putikka Research Interests Pairing Correlations for Models of Strongly Correlated Electrons ● High temperature expansions for the 2 D t-J, Hubbard Models (High Tc) ● ● Superconducting correlation length Currently no funding, but maybe by spring (grants submitted this fall) ● WO Putikka & MU Luchini PRL 96, 247001 (1996) ● Spin Lifetimes in Semiconductors Relaxation of nonequilibrium spin distributions by a range of physical processes ● Relevant for Spintronics ● Maybe relevant for Quantum Computing • Currently supporting one grad student, Nick Harmon ● WO Putikka & R Joynt PRB 70, 113201 (2004) ● Physics 795: CMT - Nov 3, 2006 5

Mohit Randeria Strongly interacting Quantum many-body systems • Superconductivity in doped Mott insulators - High Tc superconductors • Angle-resolved photoemission spectroscopy of complex materials • Cold atoms: superfluidity & BCS-BEC crossover Group members: Rajdeep Sensarma (Ph. D student) Roberto Diener (Post-doctoral. Physics research associate) 795: CMT - Nov 3, 2006 6

DAVID STROUD: RESEARCH INTERESTS • HIGH-Tc SUPERCONDUCTORS. • We are studying electronic properties of these materials. QUBITS. We try to invent controllable two-level systems out of superconductors, for ``quantum computing. ’’ • NANOSCALE OPTICAL MATERIALS. Tiny metal grains in air or glass (or linked together with strands of DNA) have unique optical properties, and aggregate at low temperatures • More information at /~stroud/Research. html Lin ker DN A Physics 795: CMT - Nov 3, 2006 7

Nandini Trivedi BIG PICTURE Condensed Matter Theory How do many electrons organise themselves? The magic of quantum mechanics and statistical mechanics! NEW PHASES AND QUANTUM PHASE TRANSITIONS Some of the most challenging problems in condensed matter today deal with new phases of matter generated by strong interactions between the constituents. Disorder in such correlated systems can produce novel effects. Techniques: semianalytical; Quantum Monte Carlo techniques matlab; mathematica My Group: Grad Students: Kohjiro Kobayashi- Metal Insulator transition Rajdeep Sen. Sarma – High Tc Superconductivity (jointly with M. Randeria) Vamsi Akkineni – BCS-BEC Crossover in Ultracold Atoms (jointly with D. Ceperley, Urbana) Undergraduates: Tim Arnold– Nano Superconductors Eric Wolf– Dynamics of quantum systems Group meetings: every Friday at noon E-mail ME IF YOU ARE INTERESTED Opening for at least 1 grad student Other collaborations on Superconductor-Insulator Transition (Berkeley); Optical Lattices (ISSP, Tokyo and Trento, Italy) Physics 795: CMT - Nov 3, 2006 8

John Wilkins 1. Predicting bandgap offsets of semiconductor heterostructures. The aim is to provide predictive data for scientists and engineers designing new semiconductor devices. Currently there is lot of trial and error (called combinatorial synthesis) to find desired band gaps and the offset of valence and conduction bands. Current method are seldom better than a factor of two (useless!). 2. Predicting defect formation and evolution in semiconductors and metals. Today we have simple pictures that we believe are quantitative for motion of small interstitial clusters in silicon and alpha->omega phase transition in titanium. Interest in the first is to eventually understand how large defects are formed. [Generally these are undesirable. Knowing the path might lead to blocking it. ] In titanium, omega phase is brittle. This transition needs to be inhibited. Current success is again thru experimentally combinatorial methods. Anything that could shorten the process is a step forward. 3. To simulate large system -- necessary for reality -- models are necessary. We are exploiting quantum Monte Carlo methods (that, in principle can be exact) to benchmark these models. Viewgraph at http: //www. physics. ohio-state. edu/~wilkins/junk/qmc. html shows one example. Summary: Broad range of computational approaches model defect-induced properties aimed at predicting and improving properties. Benchmarking methods are essential to ensure model predictions are reliable. This double focus needs a range of skills and interest from pure to applied. Physics 795: CMT - Nov 3, 2006 9

… and the others … • Tin-Lun (Jason) Ho Fundamental issues in dilute quantum gases: Scalar and Spinor Bose condensates, Fermi gases with large spin, mixtures of quantum gases in optical lattice and rapidly rotating potential, Boson mesoscopics, processing quantum information with spinor Bose condensates; Quantum Hall effects with internal degrees of freedom; Strongly correlated electron systems; Quantum fluids • C. Jayaprakash Nonequilibrium phenomena; Fully developed turbulence; Strongly interacting fermion systems • Bruce R. Patton Structure and properties of electroceramics; Grain growth in anisotropic systems; Pattern recognition and optimization • William F. Saam Phase transitions at interfaces: wetting and roughening transitions; Step interactions on solid surfaces and consequent phase transitions Physics 795: CMT - Nov 3, 2006 10

http: //physics. ohio-state. edu/~cmt/osucmt. html Physics 795: CMT - Nov 3, 2006 11