Personal Website
Office¡G886-3-5742951(PHYS R611)

Condensed Matter Theory Group

  1. 1993-1998 Ph.D in Physics, University of California, U.S.A.
  2. 1987-1991 B.S. in Physics, National Taiwan University, R.O.C.
Professional Experience
Current position¡G
  1. 2007/08-, Professor of Physics, National Tsing Hua University
  1. 2003-2007, Associate professor at National Tsing Hua University
  2. 2006-2008, Staff Scientist, National Center for Theoretical Sciences
  3. 2004, General Member, Kavli Institute for Theoretical Physics, Santa Barbara, USA
  4. 2000-2003, Assistant Professor, National Tsing-Hua Univ., Taiwan
  5. 1999-2000, Postdoc Fellow, Indian Univ., Bloomington, USA
  6. 1993-1998, Ph.D. in Physics, Univ. of California, Santa Barbara, USA
Honors and Awards
  1. 2007, Outstanding Teacher Award
  2. 2006, Ten Outstanding Youths in Taiwan
  3. 2003-2006, Ta-You Wu Fellow, Physics Division, National Center for Theoretical Sciences, Taiwan
Research Fields
      Condensed matter theory with recent interests in the following topics:
      (1) Spintronics at nanoscale,
      (2) Low-dimensional correlated systems,
      (3) Statistical physics.
Research Interests and achievement
Updated on September 3, 2006
I started out my research career in strongly correlated electron systems. In particular, we combined Wilson¡¦s renormalization group and the non-perturbative bosonization techniques to study quasi-one-dimensional ladder materials. Not only we were among the first to pin down the phase diagram of the competing ground states, we also discovered a novel dynamical symmetry enlargement in the two-leg lad?der. In fact, it is the first time that one can obtain exact resutls/predictions for the novel spin liquid ground states.

After coming back to Taiwan in 2000, I switched research direction to work on spintronics. With Allan MacDonald's group, we successfully built up the spin-wave theory for diluted magnetic semiconductors and explained the carrier-mediated ferro?magnetism in these materials. Being one of the pioneering groups in this field, our pa?pers on this subject receive more than 300 citations by now.

In recent years, we applied the notion of carrier-mediated ferromagnetism to the exchange coupling in conventional magnetic junctions. We demonstrate how the magnetic couplings between two ferromagnetic layers depend crucially on the itinerant carriers in the intermediate layer and thus can be manipulated by electric field at ease. Surprisingly, we also discovered that the topology of the Fermi surface is closely related to the mediated exchange cou?plings.

Selected Publications
  1. [2006] W.-M. Huang, C.-H. Chang and HHL, Noncollinear exchange coupling in a trilayer magnetic junction and its connection to Fermi surface topology, Phys. Rev. B 73, 241307(R) (2006).
  2. [2006] J. E. Bunder, S.-J. Sun and HHL, Spin-wave relaxation in diluted magnetic semiconductors within self-consistent Green¡¦s function approach, Appl. Phys. Lett. 89, 072101 (2006).
  3. [2006] C.-H. Lin, HHL and T.-M. Hong, Spiral exchange coupling in trilayer magnetic junction mediated by diluted magnetic semi?conductor thin ?im, Appl. Phys. Lett. 89, 032503 (2006).
  4. [2005] A. Seidel, HHL and D.-H. Lee, Phonons in Hubbard ladders studied within the framework of one-loop renormalization group, Phys. Rev. B 71, 220501(R) (2005).
  5. [2004] S.-J. Sun, S.-S. Cheng and HHL, Spiral Exchange Interaction in Diluted Mag?netic Semiconductor Junction, Appl. Phys. Lett. 84, 2862 (2004).
  6. [2000] J. Konig, HHL and A. H. MacDonald, Theory of diluted magnetic semiconductor ferromagnetism, Phys. Rev. Lett. 84, 5628 (2000).
  7. [1998] HHL, L. Balents and M. P. A. Fisher, Exact SO(8) symmetry in the weakly-interacting two-leg ladder, Phys. Rev. B 58, 1794 (1998).
  8. [1997] HHL, L. Balents and M. P. A. Fisher, The N-chain Hubbard model in weak coupling, Phys. Rev. B 56, 6569 (1997).
    • Recent Publications (Expansible)