Numerical Studies of Cuprate High-temperature Superconductors PDF Download

Author: Yvonne Kung
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Languages : en
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Book Description
Strongly correlated electron systems exhibit a panoply of fascinating phases, such as antiferromagnetism, charge order, and unconventional superconductivity, that compete or cooperate with one another. Yet the intertwined degrees of freedom that create this complexity also obscure the underlying mechanisms, so that numerous experimental and theoretical studies have been brought to bear on these materials. This thesis provides a window on the field from the perspective of phenomenological and microscopic studies of the cuprates and nickelates. The first part presents a phenomenological model of strongly coupled orders that explains recent time-resolved x-ray diffraction experiments on the nickelates. The new experimental technique enables us to disentangle degrees of freedom that are intertwined in thermal equilibrium, motivating a need for theoretical developments. Our time-dependent Ginzburg-Landau theory facilitates an understanding of how coupled orders behave when driven out of equilibrium. The second part of the thesis explores numerical simulations of microscopic models to answer open questions in the cuprates. A comparison of spin and charge susceptibilities computed in the single-band Hubbard model via determinant quantum Monte Carlo (DQMC) to those calculated using the random phase approximation (RPA) elucidates how electronic correlations evolve throughout the phase diagram. Combined DQMC and exact diagonalization (ED) studies of the three-orbital Hubbard model systematically evaluate broken-symmetry states that have been proposed to explain the pseudogap regime. Thus the use of complementary techniques, both analytical and computational, sheds light on different ordered phases and excitations in strongly correlated systems and points the way to further studies.