Proefschrift Universiteit van Amsterdam. / Auteursnaam op omslag: Pedro Estrela. Met bibliogr., lit. opg. - Met samenvatting in het Nederlands.

Thèses (Ph.D.)--Université de Sherbrooke (Canada), 1998. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Thesis (Ph.D.)--Kent State University, 2009. / Title from PDF t.p. (viewed Apr. 3, 2010). Advisor: Almut Schroeder. Keywords: non-Fermi liquid, CeNi2Ge2, spin fluctuations, neutron scattering, heavy fermions, quantum critical point. Includes bibliographical references.

Universiẗat, Diss., 2001--München.

Th.--Sci. phys.--Nancy--I.N.P.L., 1977.

A study of the Fermi surface of copper at room temperature has been made by means of a positron annihilation technique. A positron active copper single crystal was placed midway between two “point" scintillation counters operated in time coincidence. The coincidence count rate was measured for various crystal orientations and the count rate interpreted as a measure of the diameter of the Fermi surface. The experiment yields a Fermi surface that is spherical in k-space except for protrusions in the {111} directions which are estimated to subtend an angle of about 20° at k = 0. Within experimental error the results are consistent with those obtained by other methods near 0° K. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A positron annihilation experiment involving collinear point geometry is used to make a direct comparison of the k₁₁₀ and k₁₀₀ Fermi radii in a single crystal of lithium. It is found that is k₁₁₀ greater than k₁₀₀ by 5.6 ± 1.2%, in agreement with theory and a phenomenological interpretation of an earlier long slit experiment. The higher momentum components of the positron wavefunction are calculated by a direct method and found to be negligible. On the other hand, a less straightforward estimate based on a flattened Seitz potential shows that the higher momentum components of the electron wavefunction significantly reduce the experimentally observed anisotropy. Hence, the difference of 5.6% should be regarded as an upper limit on the true distortion of the Fermi surface of lithium. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

No description available.

In this thesis, we study the low-energy effective theory for the antiferromagnetic quantum critical metal in two dimensions. The theory has been the subject of intense study for more than twenty years, due to the novel physics of non-Fermi liquid metals and its potential relevance to high-temperature superconductors and heavy-fermion compounds. In the first part of the thesis, we present the perturbative study of the theory in 3 minus epsilon space dimensions by extending the earlier one-loop analysis to higher-loop orders. We show that the expansion is not organized by the standard loop expansion, and a two-loop graph becomes as important as one-loop graphs even in the small epsilon limit due to an infrared singularity caused by an emergent quasilocality. This qualitatively changes the nature of the infrared fixed point, and the epsilon expansion is controlled only after the two-loop effect is taken into account. Furthermore, we show that a ratio between velocities emerges as a small parameter, which suppresses a large class of diagrams. We show that the critical exponents do not receive quantum corrections beyond the linear order in epsilon in the limit that the ratio of velocities vanishes. In the second part of the thesis, we present a nonperturbative solution to the theory in two dimensions based on an ansatz that is inspired by the perturbative analysis. Being a strongly coupled theory, it can still be solved reliably in the low-energy limit as quantum fluctuations are organized by the ratio of velocities that dynamically flows to zero in the low-energy limit. We predict the exact critical exponents that govern the universal scaling of physical observables at low temperatures. / Thesis / Doctor of Philosophy (PhD)