Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2008. / Includes bibliographical references (leaves 169-174). / Different experiments on strongly correlated materials have shown phenomena which are not consistent with our conventional understandings. We still do not have a general framework to explain these properties. Developing such a general framework is much beyond the scope of this thesis, but here we try to address some of challenges in simpler models that are more tractable. In correlated metals it appears as strong correlations have different effect on different parts of fermi surface. Perhaps most striking example of this is normal state of optimally doped cuprates; the quasiparticle peaks on the nominal fermi surface do not appear uniformly. We try to track such phenomena in heavy fermion systems, which are correlated fermi liquids. In these systems, a lattice of localized electrons in f or d orbitals is coupled to the conduction electrons through an antiferromagnetic coupling. Singlets are formed between localized and conduction electrons. This singlet naturally have non-zero internal angular momentum. This nontrivial structure leads to anisotropic effect of strong correlations. Internal structure of Kondo singlet can also lead to quantum Hall effect in Kondo insulator, and formation of isolated points on the fermi surface with fractionalized quasiparticles. In the second part we study a phase transition in Heisenberg model between two insulating phases, Neel ordered and certain spin liquid state, popular in theories of the cuprates. The existence of such a transition has a number of interesting implications for spin liquid based approaches to the underdoped cuprates and clarifies existing ideas for incorporating antiferromagnetic long range order into such a spin liquid based approach. This transition might also be enlightening, despite fundamental differences, for the heavy fermion critical points where a second order transition between the heavy fermion phase and a metallic phase with magnetic antiferromagnetic order is observed. / by Pouyan Ghaemi Mohammadi. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (page 59). / Most materials are either metals or insulators. When they are metals, their electronic properties are usually described by Landau's Fermi liquid theory. That is, they behave more or less like a free Fermi gas, with a few modifications due to electron-electron interactions. However, there exist a few metallic materials whose phenomenology does not fit within Fermi liquid theory. These are quasi-2D metals on the verge of becoming insulators, and they happen to become superconducting at low temperature, by a mechanism different than BCS superconductivity. The physics of these materials calls for a new strongly coupled universality class of interacting electrons, yet to be understood. This work looks at the problem from the novel point of view of gauge/gravity, or holographic, duality. / by Andrea Allais. / Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 91-95). / This thesis discusses recent experimental work in measuring the properties of higher levels in transmon qubit systems. The first part includes a thorough overview of transmon devices, explaining the principles of the device design, the transmon Hamiltonian, and general Circuit Quantum Electrodynamics concepts and methodology. The second part discusses the experimental setup and methods employed in measuring the higher levels of these systems, and the details of the simulation used to explain and predict the properties of these levels. / by Samuel James Bader. / S.B.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1999. / Includes bibliographical references (p. 179-191). / In this thesis, I report on a system I designed ad implemented to rapidly identify and localize new transient X-ray sources observed by the All-Sky Monitor (ASM) on the Rossi X-ray Timing Explorer (XTJS), I used this system to identify fourteen Gamma-Ray Bursts (GRBs). Eight of these events were found in archived ASM observations from the first 1.5 years of operation, but the rest were detected and reported within 2 - 32 hours of the event. In thirteen of the fourteen cases, I was able to provide error boxes with a reliable confidence level. I report here on the ASM instrument, the system to identify new X-ray sources, the ASM localization capability, the current state of the field of GRB studies, the thirteen GRB positions, and fourteen GRB light curves. I interpret these observations in the context of the Synchrotron Shock Model for GRB emission. / by Donald Andrew Smith. / Ph.D.

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

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2011. / In title on title-page, "[the square root of]" appears as the mathematical symbol. Cataloged from PDF version of thesis. / Includes bibliographical references (p. 237-243). / In this thesis, we perform the measurement of the production of W and Z bosons in proton-proton collisions at [the square root of]s = 7 TeV with the Large Hadron Collider (LHC). In the LHC, W and Z bosons are produced at a high rate, providing for large yields, which along with the clean signature of W boson decay into a muon and neutrino and the Z boson decay into two muons, allow for precision measurement of their production within the first year of operation. Deviation of these values from standard model predictions gives a clear indication of new physics interactions occurring at the LHC. We present the measurement of the inclusive W--> [mu] [epsilon] and Z --> [mu]+ [mu]- cross sections along with the W boson charge ratio (W+/W-) and the W/Z production ratio in the muon channel using the first data corresponding to 35.9 pb-1 of proton proton collisions at [the square root of]s = 7 TeV. Measured values of ... are in agreement with the most advanced NNLO predictions. These are currently the most precise Electroweak measurements at the LHC. / by Philip Coleman Harris. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1958. / Includes bibliographical references (leaves 50-52). / by Bernard Harold Soffer. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1995. / Includes bibliographical references. / by Uros̆ Seljak. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 145-164). / Controlled transport of energy and information is of paramount importance. It remains challenging, however, partially from the difficulty in controlling their physical carriers. Steering electrons and photons is now routine, yet atomic vibrations (quantized as phonons) are hard to control. This is partly due to the centrality of phonons in the disordered transport of energy as heat, but even in ordered sound waves problems persist. Phonons can readily couple to each other or to other degrees of freedom, degrading their energy or information content. Reversing these couplings, thereby regulating atomic motion, only recently became plausible. This increased control would reduce parasitic losses and turn phonons into information carriers. Dynamical effects are a crucial and under-examined aspect of this control as static devices are insufficient for changing external conditions. Dynamical control adds flexibility and versatility to phononic systems. Essentially, dynamical control requires tunable materials, materials whose physical properties depend on an external signal. Dynamical tuning is sensitive to the relative frequencies of the tuning signal and the controlled phonons. We develop an intuitive framework of the temporal modulation regimes. In low frequency tuning, phonons can adapt adiabatically to the material's changes. A variety of signals can be temporally and spatially modulated to tune phonon transport in this regime. We apply this adiabatic perspective to analyze dynamical effects in thermal cloaks. Tuning signals near the frequency of some phonon mode can produce resonant couplings. This hybridization can produce large changes in phonon properties. We apply this hybridization to develop a rigorously nonreciprocal phononic computer using magneto-acoustic materials that can outperform conventional computers in some tasks. At high frequencies, phonons can only respond perturbatively to the tuning signal's changes. This regime is generally limited to optical control but it opens up new avenues for control. Employing an alternative approach to optical coupling, we develop a model of inverse acousto-optics (tuning the speed of sound with optical intensity) and dynamical phonon localization. / by Sophia Robin Sklan. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1995. / Includes bibliographical references (p. 157-162). / by Kevin Earl Wilson. / Ph.D.