Postdoctoral and Research Fellows
His main research interest
involves the study of various lattice models on theoretical physics,
this includes the lattice spin and fermion models in the condensed
matter physics, and the lattice gauge theory in particle physics.
Some of these models in condensed matter physics are related to the
macroscopic quantum phenomena such as magnetism and superconductivity,
while others in quantum field theory describe the strong interactions
within the sub-nuclear particles. The study of these systems relies
on a variety of analytic and numerical techniques requiring the use
His research group has been among the world pioneers in developing
linked-cluster expansion methods for generating perturbation series
in Hamiltonian lattice models. Using this technique, they have generated
the longest series available for a variety of spin and gauge models.
For the Heisenberg antiferromagnet, their series results are very
accurate, rivalling or exceeding the best Monte Carlo estimates. His
research group has also developed the longest spin-wave perturbation
series for several lattice models.
Recently, his research group has successfully developed a linked-cluster
series expansion technique to study the properties of multi-particle
bound states and continuum. The study of multi-particle bound
states remains a challenging problem in many-body physics. The information
of multi-particle bound states is very important for understanding
the nature of low temperature quantum ground states in real experimental
systems, while a controlled numerical framework for the calculation
of multi-particle spectral properties, which can also account for
various singularities as the coupling constants are varied, is currently
missing. The development of high-order series expansion for multi-particle
bound states present significant advances. With this new technique,
they have found several new bound states on various systems, and this
approach appears to be a most productive and exciting line of development.
He is also interested on other numerical techniques, including the
the density matrix renormalization group method, the spin-wave theory,
the t-expansion method , and the finite lattice approach.
- The square lattice Heisenberg
antiferromagnet at T=0. W.H. Zheng, J. Oitmaa and C.J. Hamer, Physical
Review, B43, 8321-8330(1991).
- Spin-wave theory and finite-size
scaling for the Heisenberg antiferromagnet. W.H. Zheng and C.J.
Hamer , Physical Review, B47, 7961-7970(1993).
- Strong coupling series for
Abelian lattice gauge models in 3+1 dimensions. C.J. Hamer, J. Oitmaa
and W.H. Zheng, Physical Review, D49, 535-542 (1994).
- Convergent expansions for properties
of the Heisenberg model for CaV4O9. M.P. Gelfand, W.H. Zheng, R.R.P.
Singh, J. Oitmaa and C.J. Hamer, Physical Review Letter,
77, 2794-2797 (1996)
- Various series expansions for
the bilayer S=1/2 Heisenberg antiferromagnet. W.H. Zheng, Physical
Review B55, 12267-12275 (1997).
- Novel Approach to Description
of Spin-Liquid Phases in Low-Dimensional Quantum Antiferromagnets.
V.N. Kotov, O. Sushkov, W.H. Zheng and J. Oitmaa, Physical Review
Letter, 80, 5790-5793 (1998).
- Multi-layer S=1/2 Heisenberg
antiferromagnet, W.H. Zheng, Physical Review B59,
- Strong-Coupling Expansions
for Multiparticle Excitations: Continuum and Bound States, S. Trebst,
H. Monien, C.J. Hamer, W.H. Zheng, R.R.P. Singh, Physical Review
Letter, 85, 4373-4376(2000).
- Linked cluster series expansions
for two-particle bound states,
W.H. Zheng, C.J. Hamer, R.R. P. Singh, S. Trebst, and H. Monien,
Physical Review B63, 144410 (2001).
- Deconfinement transition and
bound states in frustrated Heisenberg chains: regimes of forced
and spontaneous dimerization, W.H. Zheng, C.J. Hamer, R.R.P. Singh,
S. Trebst, and H. Monien, Physical Review B63,
- Realization of a large J2 quasi-2D
spin-half Heisenberg system: Li2VOSiO4, H. Rosner, R.R. P. Singh,
W. H. Zheng, J. Oitmaa, S. L. Drechsler, W. E. Pickett, Physical
Review Letter, 88, 186405 (2002).
- Spectral weight contributions
of many-particle bound states and continuum, W.H. Zheng, C.J. Hamer,
and R.R.P. Singh, accepted in Physical Review Letter.
School of Physics
The University of New South Wales
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