Matching Items (3)
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- All Subjects: Nuclear spin
- All Subjects: Flow injection analysis
- Creators: Schmidt, Kevin E
- Creators: Gifford, Jessica Anna
Description
Spin-orbit interactions are important in determining nuclear structure. They lead to a shift in the energy levels in the nuclear shell model, which could explain the sequence of magic numbers in nuclei. Also in nucleon-nucleon scattering, the large nucleon polarization observed perpendicular to the plane of scattering needs to be explained by adding the spin-orbit interactions in the potential. Their effects change the equation of state and other properties of nuclear matter. Therefore, the simulation of spin-orbit interactions is necessary in nuclear matter.
The auxiliary field diffusion Monte Carlo is an effective and accurate method for calculating the ground state and low-lying exited states in nuclei and nuclear matter. It has successfully employed the Argonne v6' two-body potential to calculate the equation of state in nuclear matter, and has been applied to light nuclei with reasonable agreement with experimental results. However, the spin-orbit interactions were not included in the previous simulations, because the isospin-dependent spin-orbit potential is difficult in the quantum Monte Carlo method. This work develops a new method using extra auxiliary fields to break up the interactions between nucleons, so that the spin-orbit interaction with isospin can be included in the Hamiltonian, and ground-state energy and other properties can be obtained.
The auxiliary field diffusion Monte Carlo is an effective and accurate method for calculating the ground state and low-lying exited states in nuclei and nuclear matter. It has successfully employed the Argonne v6' two-body potential to calculate the equation of state in nuclear matter, and has been applied to light nuclei with reasonable agreement with experimental results. However, the spin-orbit interactions were not included in the previous simulations, because the isospin-dependent spin-orbit potential is difficult in the quantum Monte Carlo method. This work develops a new method using extra auxiliary fields to break up the interactions between nucleons, so that the spin-orbit interaction with isospin can be included in the Hamiltonian, and ground-state energy and other properties can be obtained.
ContributorsZhang, Jie (Author) / Schmidt, Kevin E (Thesis advisor) / Alarcon, Ricardo (Committee member) / Lebed, Richard (Committee member) / Shumway, John (Committee member) / Arizona State University (Publisher)
Created2014
Description
Sample delivery is an essential component in biological imaging using serial diffraction from X-ray Free Electron Lasers (XFEL) and synchrotrons. Recent developments have made possible the near-atomic resolution structure determination of several important proteins, including one G protein-coupled receptor (GPCR) drug target, whose structure could not easily have been determined otherwise (Appendix A). In this thesis I describe new sample delivery developments that are paramount to advancing this field beyond what has been accomplished to date. Soft Lithography was used to implement sample conservation in the Gas Dynamic Virtual Nozzle (GDVN). A PDMS/glass composite microfluidic injector was created and given the capability of millisecond fluidic switching of a GDVN liquid jet within the divergent section of a 2D Laval-like GDVN nozzle, providing a means of collecting sample between the pulses of current XFELs. An oil/water droplet immersion jet was prototyped that suspends small sample droplets within an oil jet such that the sample droplet frequency may match the XFEL pulse repetition rate. A similar device was designed to use gas bubbles for synchronized “on/off” jet behavior and for active micromixing. 3D printing based on 2-Photon Polymerization (2PP) was used to directly fabricate reproducible GDVN injectors at high resolution, introducing the possibility of systematic nozzle research and highly complex GDVN injectors. Viscous sample delivery using the “LCP injector” was improved with a method for dealing with poorly extruding sample mediums when using full beam transmission from the Linac Coherent Light Source (LCLS), and a new viscous crystal-carrying medium was characterized for use in both vacuum and atmospheric environments: high molecular weight Polyethylene Glycol.
ContributorsNelson, Garrett Charles (Author) / Spence, John C (Thesis advisor) / Weierstall, Uwe J (Thesis advisor) / Schmidt, Kevin E (Committee member) / Beckstein, Oliver (Committee member) / Arizona State University (Publisher)
Created2015
Description
A theoretical study of a three-dimensional (3D) N/S interface with arbitrary spin
polarization and interface geometry is presented. The 3D model gives the same intrinsic
spin polarization and superconducting gap dependence as the 1D model. This
demonstrates that the 1D model can be use to t 3D data.
Using this model, a Heusler alloy is investigated. Andreev reflection measurements
show that the spin polarization is 80% in samples sputtered on unheated MgO(100)
substrates and annealed at high temperatures. However, the spin polarization is
considerably smaller in samples deposited on heated substrates.
Ferromagnetic FexSix alloys have been proposed as potential spin injectors into
silicon with a substantial spin polarization. Andreev Reflection Spectroscopy (ARS) is
utilized to determine the spin polarization of both amorphous and crystalline Fe65Si35
alloys. The amorphous phase has a significantly higher spin polarization than that of
the crystalline phase.
In this thesis, (1111) Fe SmO0:82F0:18FeAs and Pb superconductors are used to
measure the spin polarization of a highly spin-polarized material, La0:67Sr0:33MnO3.
Both materials yield the same intrinsic spin polarization, therefore, Fe-superconductors
can be used in ARS. Based on the behavior of the differential conductance for highly
spin polarized LSMO and small polarization of Au, it can be concluded that the Fe-Sc
is not a triplet superconductor.
Zero bias anomaly (ZBA), in point contact Andreev reflection (PCAR), has been
utilized as a characteristic feature to reveal many novel physics. Complexities at a
normal metal/superconducting interface often cause nonessential ZBA-like features,
which may be mistaken as ZBA. In this work, it is shown that an extrinsic ZBA,
which is due to the contact resistance, cannot be suppressed by a highly spin-polarized
current while a nonessential ZBA cannot be affected the contact resistance.
Finally, Cu/Cu multilayer GMR structures were fabricated and the GMR% measured
at 300 K and 4.5 K gave responses of 63% and 115% respectively. Not only
do the GMR structures have a large enhancement of resistance, but by applying an
external magnetic eld it is shown that, unlike most materials, the spin polarization
can be tuned to values of 0.386 to 0.415 from H = 0 kOe to H = 15 kOe.
polarization and interface geometry is presented. The 3D model gives the same intrinsic
spin polarization and superconducting gap dependence as the 1D model. This
demonstrates that the 1D model can be use to t 3D data.
Using this model, a Heusler alloy is investigated. Andreev reflection measurements
show that the spin polarization is 80% in samples sputtered on unheated MgO(100)
substrates and annealed at high temperatures. However, the spin polarization is
considerably smaller in samples deposited on heated substrates.
Ferromagnetic FexSix alloys have been proposed as potential spin injectors into
silicon with a substantial spin polarization. Andreev Reflection Spectroscopy (ARS) is
utilized to determine the spin polarization of both amorphous and crystalline Fe65Si35
alloys. The amorphous phase has a significantly higher spin polarization than that of
the crystalline phase.
In this thesis, (1111) Fe SmO0:82F0:18FeAs and Pb superconductors are used to
measure the spin polarization of a highly spin-polarized material, La0:67Sr0:33MnO3.
Both materials yield the same intrinsic spin polarization, therefore, Fe-superconductors
can be used in ARS. Based on the behavior of the differential conductance for highly
spin polarized LSMO and small polarization of Au, it can be concluded that the Fe-Sc
is not a triplet superconductor.
Zero bias anomaly (ZBA), in point contact Andreev reflection (PCAR), has been
utilized as a characteristic feature to reveal many novel physics. Complexities at a
normal metal/superconducting interface often cause nonessential ZBA-like features,
which may be mistaken as ZBA. In this work, it is shown that an extrinsic ZBA,
which is due to the contact resistance, cannot be suppressed by a highly spin-polarized
current while a nonessential ZBA cannot be affected the contact resistance.
Finally, Cu/Cu multilayer GMR structures were fabricated and the GMR% measured
at 300 K and 4.5 K gave responses of 63% and 115% respectively. Not only
do the GMR structures have a large enhancement of resistance, but by applying an
external magnetic eld it is shown that, unlike most materials, the spin polarization
can be tuned to values of 0.386 to 0.415 from H = 0 kOe to H = 15 kOe.
ContributorsGifford, Jessica Anna (Author) / Chen, Tingyong (Thesis advisor) / Bennett, Peter (Committee member) / Nemanich, Robert (Committee member) / Tsen, Kong-Thon (Committee member) / Arizona State University (Publisher)
Created2015