Group:Research Talk
Title: The ground state phase diagram of the spin 1/2 J1-J2 Antiferromagnetic Heisenber
Speaker: Ling Wang University
Time: 2011-12-14 15:30-2011-12-14 16:30
Venue: FIT 1-222


The spin 1/2 J1-J2 Antiferromagnetic Heisenberg model on square lattice has raised great attention for its intriguing quantum phase transition and possible exotic phases. Due to its frustrated nature, a large scale low temperature quantum Monte Carlo study is prohibited. A tensor network variational wavefunction ansatz, on the other hand, suites very well to describe the strongly correlated quantum many body systems, and the tensor network method is free of the negative sign problem due to its variational nature. We thus explore the ground state phase diagram of this model via a tensor network approach.

Using a recently proposed cluster update algorithm for tensor network states, we are able to access the tensor network ground state with a virtual bond dimension D up to 9. We observed a second order quantum phase transition from an antiferromagnetic ordered phase to a paramagnetic disordered phase at a critical point J2_c = 0.47. The paramagnetic disordered phase preserves all symmetries of the Hamiltonian and does not have any local order. A spin liquid nature of this disordered paramagnetic state is very likely. We further studied the topological entanglement entropy of the disordered paramagnetic phase and discovered that it belongs to the Z2 topological class.


1. L. Wang and F. Verstaete, arXiv: 1110.4362.

2. L. Wang, Z.-C. Gu, X.-G. Wen, A. W. Sandvik, and F. Verstraete, work in preparation.

Short Bio:

Dr. Ling Wang currently works as a postdoc in the group of Prof. Frank Verstraete at University of Vienna in Austria. Her research mainly focuses on the numerical simulation of the strongly correlated quantum many-body physics. She had her Ph.D. from Boston University in 2009 under the supervision of Prof. Anders Sandvik. She is a specialist both in Quantum Monte Carlo and Tensor Network related methods.