### Session T26: Focus Session: Computational Frontiers in Quantum Spin Systems II

2:30 PM–5:30 PM, Wednesday, February 29, 2012
Room: 257B

Chair: Hans Gerd Evertz, Technical University of Graz

Abstract ID: BAPS.2012.MAR.T26.11

### Abstract: T26.00011 : Zero- vs. finite-field transition in S=1 Heisenberg antiferromagnet with single-ion anisotropy

4:54 PM–5:06 PM

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#### Authors:

Pinaki Sengupta
(Nanyang Technological University, Singapore)

Ian Yap
(Nanyang Technological University, Singapore)

Zhifeng Zhang
(Nanyang Technological University, Singapore)

We use large scale quantum Monte Carlo simulation on finite size lattices to study the ground state and finite temperature transitions in a $S=1$ Heisenberg antiferromagnet (HAFM) with single-ion anisotropy ($D$) in the presence of an external magnetic field ($h_z$). The ground state phase diagram (in the $h_z-D$ plane) is characterized by a quantum paramegnetic phase (QPM) at large $D$ and small $h_z$ and an XY-AFM phase at small $D$ and/or large $h_z$ separated by a continuous transition. We show that the QPM to XY-AFM transition belongs to the XY universality class at $h_z=0$ (driven by varying $D$) whereas it belongs to the BEC universality class at $h_z\neq 0$ (driven by either varying $D$ at constant $h_z$ or varying $h_z$ at constant $D$). This has important implication in the behavior of the specific heat at the transition point which can be verified experimentally. Finally, we discuss the experimental relevance of our results in the case of DTN.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.T26.11