NMR Roster at CSULA Physics * Alhambra High School (3) -James Luo -Amy Tang -Dana Zhang
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Frequency (kH z) -60 -40 -20 0 20 40 60 80 Intensity (A U ) 0.00 0.02 0.04 0.06 0.08 0.10 (M Hz) 203.68 203.72 203.76 ( s 1 ) 0.0 0.5 1.0 1.5 Tem perature (K ) K 0.5 1.0 1.5 2.0 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: URu 2 Si 2 and UCu 5-x Ni x . 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 For URu 2 Si 2 , 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] For UCu 5-x Ni x , 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]. T = 4.2 K µSR Data URu 2 Si 2 UCu 4 Ni Above: transverse field (H=1.5 T) SR parameters as functions of temperature obtained from muon asymmetry fits to a stretched exponential function exp[-( t) 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 (a) (b) (c) Frequency (kH z) -40 -20 0 20 40 60 Intensity (A U ) 0.00 0.05 0.10 Fit D ata NMR Spectra The graph below illustrates the changes in 29 Si NMR spectra obtained for a completely randomly oriented powder sample. The inset shows the spectral shape above the hidden order transition temperature (T 0 =17.5 K). The main panel shows that, below T 0 , the spectral features completely change. This might be indicative of a time-reversal symmetry breaking effect. T = 20 K
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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 - PowerPoint PPT Presentation
Transcript of NMR Roster at CSULA Physics * Alhambra High School (3) -James Luo -Amy Tang -Dana Zhang
Frequency (kHz)
-60 -40 -20 0 20 40 60 80
Inte
nsi
ty (
AU
)
0.00
0.02
0.04
0.06
0.08
0.10
(M
Hz)
203.68
203.72
203.76
( s
1)
0.0
0.5
1.0
1.5
Temperature (K)
K
0.5
1.0
1.5
2.0
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.
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
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]
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].
T = 4.2 K
µSR Data
URu2Si2
UCu4Ni
Above: transverse field (H=1.5 T) SR parameters as functions of temperature obtained from muon asymmetry fits to a stretched exponential function exp[-( t) 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 (b) Relaxation rate (c) Exponent K. The data show strong magnetic disorder effects.
(a)
(b)
(c)
Frequency (kHz)
-40 -20 0 20 40 60
Inte
nsi
ty (
AU
)
0.00
0.05
0.10
FitData
NMR Spectra
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.
T = 20 K
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
NMR Studies of Hidden Order and Quantum CriticalityOscar Bernal, California State University, Los Angeles, DMR 0604015
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.
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.
