Xu Bo-Wei

Charge Gap in One-Dimensional Extended Hubbard Model*

By using the bosonization and renormalization group methods, we have studied the low energy physical properties in one-dimensional extended Hubbard model. The formation of charge and spin gaps is investigated at the half-filled electron band. An analytical expression for the charge gap in terms of the Coulomb repulsive interaction strength U and the nearest-neighbour interaction parameter V is obtained.

Ising Transition in Dimerized XY Quantum Spin Chain

In the present paper, we proposed a simple spin-1/2 model which provides a exactly solvable example to study the Ising criticality with central charge c=1/2. By mapping it onto the real Majorana fermions, the Ising critical behavior is explored explicitly, although its bosonized form is not the double frequency sine-Gordon model.We proposed a simple spin-1/2 model which provides an exactly solvable example to study the Ising criticality with central charge . By mapping it onto the real Majorana fermions, the Ising critical behavior is explored explicitly, although its bosonized form is not the double frequency sine-Gordon model.

Charge and spin gaps in the dimerized Hubbard model

By using the bosonization and renormalization group methods, we have studied the low energy physical properties in the one-dimensional dimerized Hubbard model. The formation of charge and spin gaps is investigated both for the half-filled electron band and away from the half-filled band. The scaling laws of the charge and spin gaps with the dimerization parameter Δ and the repulsive interaction strength U are obtained.

Renormalization Group Study of Ising Transition in Double-Frequency sine-Gordon Model*

We utilize the renormalization group (RG) technique to analyze the Ising critical behavior in the double frequency sine-Gordon model. The one-loop RG equations obtained show unambiguously that there exist two Ising critical points besides the trivial Gaussian fixed point. The topology of the RG flows is obtained as well.

Properties of Coherent State for Hydrogen Atom

We construct the coherent state for the two-dimensional hydrogen atom, for which the averaged motion of position describes a Kepler ellipse. The coherent state can be expanded with respect to the eigenstates of 2D hydrogen atom, from which we evaluate the binding energy of the wave packet for this state.

Liquid-Gas Transition in the Ionic System

The phase transition in the ionic system in dimension d = 3 is studied in the formulation of quantum sine-Gordon field theory. By a variational method the phase diagram is investigated, and the critical point terminating the coexistence of conducting liquid and conducting gas is obtained

CRITICAL EXPONENTS OF THE ONE-DIMENSIONAL CONTINUUM HEISENBERG-ISING MODEL

The continuum generalization of the one-dimensional Heisenberg-Ising model is studied by the bosonization method. With reference to the results of the renormalization group theory, we are able to obtain the critical exponents by considering the influence of the large momentum transfer and improve Luther and Peschels results to the next order. A comparison of the exact result of the lattice model with that of the continuum model by various treatments are also given.

Electron Transport Through Double-Dot Aharonov-Bohm Interferometer in the Kondo Regime*

By applying the slave boson technique, we have studied the electron transport through double-dot Aharonov–Bohm interferometer in the Kondo regime. For the system with symmetric quantum dots, the linear conductance is shown to be enhanced by Kondo effect, but it is suppressed in the deep dot level regime in the presence of nonzero magnetic flux. The Aharonov–Bohm oscillations of the conductance are also investigated.

The Numerical Study of the S = 1/2 XXZ Chain

We adopt the Lanczos method combined with the quantum conformal field theory to investigate the S = 1/2 XXZ chain in detail. The bulk-limit ground state energy, the anomalous scaling dimension of the spin operators, the Fermi velocity and the zero-temperature susceptibility are numerically calculated. The results agree to the exact solution well.

Phase Transition of Spin-Peierls Systems with Impurities

The quasi-one-dimensional spin-Peierls (SP) systems with impurities are studied in their bosonized form. The spins of the dimerized state are bounded into singlets with an SP gap, while the impurities of doped systems will induce fluctuations of the coupling strength between the spins at different sites and break some pairs of spin singlets. The doping suppresses the dimerized SP state and induces a Kosterlitz-Thouless phase transition from the dimerized state into the undimerized one.