UBC Theses and Dissertations
The stripe phase in 4-leg ladders and quantum impurity entanglement Chang, Ming-Shyang
The physics of ladder systems and the Kondo problem have an essentially one-dimensional nature. There are powerful tools, such as bosonization and conformal field theory, applicable to these systems. In the first part of this dissertation, the stripe phase in 4-leg ladders is investigated by bosonization and weak-coupling renormalization group equations. A new type of charge-four correlation, bipairing, is proposed and gives a simple explanation of the stripe phase. In the second part, we discuss boundary effects on the entanglement entropy in quantum spin chains and calculate the entanglement entropy in the Kondo-like quantum impurity model. The result on impurity entanglement entropy is generalized to the system with finite size or finite temperature by employing conformal field theory methods. The theoretical calculations are also compared with numerical results obtained by density matrix renormalization group methods.
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