Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1965. Ph.D. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1960. / MIT copy bound with: A gas Cerenkov threshold detector to measure the peak energy of the bremsstrahlung beam of the M. I. T. synchrotron / Robert Murano. 1960. -- Magnetic moments of MN⁵²m and MN⁵⁴ / Gordon S. Mutchler. 1960. -- A proposed experiment to measure the parameters of lambda hyperon decay / James Wilcox Overbeck. 1960. -- General data reduction of curved crystal spectrograph and analysis of fission-fragment gamma rays from MITR / Nam Chin Paik. 1960. -- A study of [pi⁺] photoproduction in carbon by means of a nine inch propane bubble chamber / Robert Peter Perrin. 1960. -- Liquid nitrogen cooler for use on a single crystal neutron spectrometer / Winthrop Risk. 1960. -- Reaction time of the extensor digitorum communis / Donald Sashin. 1960. / by Charles H. Moore. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009. / Includes bibliographical references (p. 51-54). / In this thesis, I develop a new, field-theoretic method for describing the quantum phase transition between Mott insulating and superfluid states observed in bosonic optical lattices. I begin by adding to the Hamiltonian of interest a symmetry breaking source term. Using time-dependent perturbation theory, I then expand the grand-canonical free energy as a double power series in both the tunneling and the source term. From here, an order parameter field is introduced, and the underlying effective action is derived via a Legendre transformation. After determining the Ginzburg-Landau expansion of the effective action to first order in the tunneling term. expressions for the Mott insulator-superfluid phase boundary, condensate density, average particle number, and compressibility are derived and analyzed in detail. Additionally, excitation spectra in the ordered phase are found by considering both longitudinal and transverse variations of the order parameter. Finally, these results are applied to the concrete case of the Bose-Hubbard Hamiltonian on a three dimensional cubic lattice, and compared with the corresponding results from mean-field theory. Although both approaches yield the same Mott insulator - superfluid phase boundary to first order in the tunneling, the predictions of the effective action theory turn out to be superior to the mean-field results deeper into the superfluid phase. / by Barry J. Bradlyn. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1986. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Bibliography: leaves 165-168. / by Roland Kraft Vanderspek. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1989. / Title as it appears in the M.I.T. Graduate List, Sept. 1989: Neutron scattering studies of the dynamics and magnetism and lattice dynamics in La₂₋x̳Srx̳CuO₄. On t.p. double underscores indicate subscript. / Includes bibliographical references. / by Thomas Raymond Thurston. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1995. / Includes bibliographical references. / by Esko Olavi Keski-Vakkuri. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004. / Includes bibliographical references (p. 40-41). / The discovery of unconventional superconductivity in hydrated Na₀Ì£₃CoO₂·1.3H₂0 has lead to active research work on the material over the last year due to its similarities and possible insight into the high-T[sub]c copper oxide superconductors as well as the possibility of other rich physical phenomenon. In this thesis, experimental evidence is presented illustrating the existence and properties of a previously unknown non-superconducting phase of Na₀Ì£₃CoO₂·1.3H₂0. This evidence includes magnetic susceptibility and x-ray scattering studies which suggest that the appearance of this phase is not due to underhydration and that a superconducting state can be restored via annealing at temperatures above roughly 340 K. Furthermore, synchrotron x-ray scattering of the non-superconductor reveals a 3-c modulation which is clearly absent in the superconducting phase of the material as well as unexpected temperature dependence behavior in the associated Bragg peaks. / by Daniel Robert Garcia. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 191-206). / In this thesis, I explore three classes of quantum phases of matter that cannot be understood purely on the basis of symmetry, and can be regarded (to varying degrees) as having highly-entangled ground-states. The first Part describes topological superconductors with non-Abelian defects, and develops realistic routes to constructing these exotic superconductors from more elementary materials. Particular attention is payed to practical issues such as disorder. The second Part examines the role of interactions in electron topological insulators (TIs). Non-perturbative definitions of the familiar topological band-insulator are given, and new strongly-correlated TIs with no band-structure analogs are identified. The last Part turns exotic gapless phases without quasi-particle excitations, focusing on topics related to recently discovered quantum spin-liquid (QSL) materials. The possibility of a gapless QSL in the vicinity of the metal-insulator transition in doped semiconductors is explored, and optical conductivity is developed as an experimental tool to examine the nature of the QSL candidate Herbertsmithite. The material of this thesis is closely parallels that of Refs [1, 2, 3, 4, 5, 7,8, 9,10, 11]. / by Andrew C. Potter. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2001. / Includes bibliographical references (leaves 121-128). / In recent years branes have had significant impact in the construction of higher dimensional theories of SUSY breaking, and of gravitational phenomena. In particular they provide strong motivation for considering anomaly mediation as a mechanism of SUSY breaking communication. Anomaly mediation provides a very predictive spectrum for the superpartner masses, which is quite model independent, and is given in terms of the beta functions and anomalous dimensions of the fields. This spectrum is also largely flavor blind, and thus does not suffer from flavor changing neutral current problems. Anomaly mediation, however, predicts negative slepton mass squardes. In this thesis we will try to address this problem by providing positive contributions to the slepton masses, through higher order SUSY breaking effects stemming from having additional heavy fields in the theory. We will also provide natural values for the Au and B parameters of the MSSM. Branes also allow for the surprising possibility that we may be living in a world with infinite extra dimensions with minor observational consequences. In this dissertation we will show that the RS2 and LR models, which have a single infinite dimension, are completely consistent and conform nicely with current experiments. We will also comment on possible holographic interpretations of these models as having 4D gravity coupled to a fully quantum conformal field theory. / by Emanuel Katz. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1987. / M.I.T. copy lacks leaf 267. / Includes bibliographies. / by John W. Steinbeck. / Ph.D.