PhD, The University of Texas at Austin, 2003-2008
M.S., National Taiwan University, 1999-2002
B.S., National Taiwan University, 1995-1999

Experience

Research Assistant
Institute of Physics , Academia Sinica (2002-2003)

Current Research Projects

Application of Time-Dependent Hartree-Fock Theory

I am using the time-dependent Hartree-Fock theory (TDHFT) to study the collective modes of several strongly correlated systems. TDHFT is equivalent to the generalized RPA which includes both the bubble and ladder diagrams of vertex corrections. Therefore it is a powerful tool to evaluate corrections due to quantum fluctuations at zero temperature numerically.
       The first application of TDHFT is to the 41 meV resonance mode observed in the inelastic neutron scattering measurement for high-Tc cuprates. We recently find that there is a conjugation relation, which has not been emphasized in previous study, between the antiferromagnetic fluctuation and phase fluctuation of the superconducting order parameter. Consequently, we propose that the 41 meV resonance mode is a collective mode mixing the antiferromagnetic and phase fluctuations. This new picture not only explains several unsolved puzzles, but also leads to the conclusion that this collective mode is responsible for the suppression of superfluid density. We have developed a TDHFT on the generalized Hubbard model with nearest neighbor attractive interaction and obtained a quantitative support for our new picture.
       Another application of TDHFT is to the graphene. Graphene has attracted enormous attentions due to its peculiar Dirac-like quasi-particles near the Fermi surface. However, just because of the Dirac-like quasi-particles making graphene a gapless semiconductor, the Coulomb interaction is poorly screened and therefore has important effects on the physical properties of graphene. We are trying to study the cyclotron frequency of a grapheme sheet under strong magnetic field using the TDHFT.

Oxide Heterostructures

       Transition metal-oxide materials have been intriguing systems in condensed matter physics for couples of years. They are also known as strongly correlated systems. In this kind of system, some conventional concepts in condensed matter physics may fail due to strong interactions between electrons. High-Tc material is one of them too. Recent experiment and some theoretical works showed that in the heterojuctions made by different transition metal oxide materials, the interface properties can be very different from the bulk properties, implying richer phase diagram of this system. Motivated by this, we are trying to systematically study heterostructures using various approaches. We expect more and more new physics will come out due to this project.

Publications

Title:ARPES, Neutrons, and the High-Tc Mechanism
Authors: Wei-Cheng Lee and A.H. MacDonald
Publication: cond-mat/0804.0356, submitted to Phys. Rev. B.

Title:Theory of Reduced Superfluid Density in Underdoped Cuprate Superconductors
Authors: Wei-Cheng Lee, Jairo Sinova, A.A. Burkov, Yogesh Joglekar, and A.H. MacDonald
Publication: cond-mat/0711.1192, Phys. Rev. B 77, 214518 (2008).

Title:Electronic Interface Reconstruction at Polar-Nonpolar Mott Insulator Heterojunctions
Authors: Wei-Cheng Lee and A.H. MacDonald
Publication: cond-mat/0705.3618, Phys. Rev. B 76, 075339 (2007).

Title:Hubbard-Thomas-Fermi Theory of Transition Metal Oxide Heterostructures
Authors: Wei-Cheng Lee and A.H. MacDonald
Publication: cond-mat/0708.0554, Proceedings of SCES'07, Physica B 403, 1558 (2008).

Title:Modulation Doping near Mott-Insulator Heterojunctions
Authors: Wei-Cheng Lee and A.H. MacDonald
Publication: cond-mat/0606200. Phys. Rev. B 74, 075106 (2006).

Title:Edge Magnetoplasmons in Quantum Hall Line Junction Systems
Authors: Wei-Cheng Lee, N. A. Sinitsyn, E. Papa, and A.H. MacDonald
Publication: cond-mat/0507227. Phys. Rev. B 72, 121304(R) (2005).

Title: Low-energy spectra in the t-J type models at light doping
Authors: Wei-Cheng Lee, T.K. Lee, Chang-Ming Ho, and P. W. Leung
Publication: Phys. Rev. Lett. 91, 057001 (2003)

Title: Theory for Slightly Doped Antiferromagnetic Mott Insulators
Authors: T.K. Lee, Chang-Ming Ho, Naoto Nagaosa, and Wei-Cheng Lee
Publication: J. of Low Temp. Phys. 131<3-4>, p169 (2003)

Title: Low-energy states in a quantum dot obtained by the orbital integration method
Authors: Wei-Cheng Lee and T. K. Lee
Publication: J. of Phys.: Condens. Matt. 14, p1045 (2002)