Berlin 2012 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 5: Spin Structures and Magnetic Phase Transitions
MA 5.2: Vortrag
Montag, 26. März 2012, 09:45–10:00, H 0112
Frustrated Ising spins simulated by spinless bosons in a tilted lattice: from disordered quantum liquids to antiferromagnetic order — •Susanne Pielawa1,2, Erez Berg1, and Subir Sachdev1 — 1Department of Physics, Harvard University, Cambridge MA 02138, USA — 2Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot, 76100 Israel
Recently a quantum antiferromagnetic spin chain has been simulated experimentally using spinless bosons in a tilted optical lattice [Nature 472, 307 (2011)]. Extending this idea to two dimensions, we theoretically analyze a setup of spinless bosons in a decorated square lattice tilted along the diagonal. This system simulates a quantum Ising model with antiferromagnetic interactions on a non-bipartite lattice. The lattice geometry thus prevents the system from ordering, even in the limit where the effective antiferromagnetic coupling is strong compared to the magnetic fields. This frustration can be reduced by changing the tilt angle slightly away from the diagonal, and the system undergoes a transition to an antiferromagnetically ordered state. We find that the disordered liquid-like state is continuously connected a the paramagnetic state. Using quantum Monte Carlo simulations and exact diagonalization we find that for realistic system sizes the antiferromagnetic order will appear to be one-dimensional; however in the thermodynamic limit the order is two-dimensional.