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NMR Roster at CSULA Physics * Alhambra High School (3) -James Luo -Amy Tang -Dana Zhang

NMR Studies of Hidden Order and Quantum Criticality Oscar Bernal, California State University, Los Angeles, DMR 0604015. NMR Roster at CSULA Physics * Alhambra High School (3) -James Luo -Amy Tang -Dana Zhang * CSULA undergraduates (6) -Daniel Marin -Chris Gutierrez

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NMR Roster at CSULA Physics * Alhambra High School (3) -James Luo -Amy Tang -Dana Zhang

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  1. NMR Studies of Hidden Order and Quantum Criticality Oscar Bernal, California State University, Los Angeles, DMR 0604015 NMR Roster at CSULA Physics * Alhambra High School (3) -James Luo -Amy Tang -Dana Zhang * CSULA undergraduates (6) -Daniel Marin -Chris Gutierrez -Pavel Pisarev -Kyle Irwin -Jacqueline Fernandez -Jennifer Plascencia * CSULA graduates (MS): -Seunghun Jung This project seeks to understand the behavior of electron correlated materials from a microscopic point of view by carrying out nuclear magnetic resonance (NMR) and muon spin rotation (µSR) measurements in two characteristic systems: URu2Si2 and UCu5-xNix. For URu2Si2, our NMR research is addressing questions on the nature of its “hidden order” phase and the possible existence of an associated time-reversal symmetry breaking effect. [see e.g.PRL 87 (2001) 196402] The graph below illustrates the changes in 29Si NMR spectra obtained for a completely randomly oriented powder sample. The inset shows the spectral shape above the hidden order transition temperature (T0=17.5 K). The main panel shows that, below T0 , the spectral features completely change. This might be indicative of a time-reversal symmetry breaking effect. For UCu5-xNix, we are addressing questions regarding the role of disorder and universality in its quantum critical and NFL (non-Fermi Liquid) regimes [see e.g. PRL 75 (1995) 2023]. (a) UCu4Ni NMR Spectra T = 20 K µSR Data (b) (c) T = 4.2 K URu2Si2 Above: transverse field (H=1.5 T) mSR parameters as functions of temperature obtained from muon asymmetry fits to a stretched exponential function exp[-(Lt)K] for which K = 2 (1) corresponds to homogeneous Gaussian (exponential) relaxation. Other values of K are indicative of static magnetic inhomogeneity in the sample [see J. Phys Cond. Matter, 16 (2004) S4479-S4498]. (a) Muon precession frequency n (b) Relaxation rate L (c) Exponent K. The data show strong magnetic disorder effects.

  2. NMR Studies of Hidden Order and Quantum CriticalityOscar Bernal, California State University, Los Angeles, DMR 0604015 Probing Hidden Order and Magnetic Disorder in Correlated Electron Systems Using Spin Probes, DMR-0203524 Probing Hidden Order and Magnetic Disorder in Correlated Electron Systems Using Spin Probes, DMR-0203524 In collaboration with K-12 teachers in the Los Angeles area we are developing instructional improvements and tools based on training and coaching of teachers in experimental techniques, complemented by science field trips and laboratory exercises for students. At right and above are pictures taken during a regular field trip to CSULA by students from Allesandro Elementary School in Los Angeles (3rd to 6th grade). High school students are also involved in our research.

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