Hamburg 2009 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 7: Quantengase: Bosonen im Gitter I

Q 7.8: Vortrag

Montag, 2. März 2009, 15:45–16:00, VMP 6 HS-A

Phase diagram of the two-dimensional spin-1/2 XY anisotropic triangular lattice — •Roman Schmied¹, Philipp Hauke¹, Tommaso Roscilde², and J. Ignacio Cirac¹ — ¹MPI für Quantenoptik, Garching, Germany — ²Ecole Normale Supérieure de Lyon, France

Quantum simulators promise to further our understanding of condensed-matter systems which are currently at or beyond the limits of computational methods. One such system is the two-dimensional spin-1/2 XY anisotropic triangular lattice [1], which we have studied using several techniques (Lanczos diagonalization, spin waves, and PEPS [2]). We present its proposed temperature-dependent phase diagram, which includes 1D and 2D Néel ordered phases, a 2D spiraling ordered phase, and several spin-liquid phases. The zero-temperature quantum phase transitions between ordered phases appear to acquire a universal discontinuous structure, passing through a short-range spin-liquid phase similar to what has been predicted for the analogous Heisenberg model. At finite temperatures, Kosterlitz-Thouless and spin-melting transitions complete the picture. We also present preliminary results on the J1-J2-J3 model.

[1] R. Schmied et al., NJP 10 (2008) 045017

[2] F. Verstraete and J. I. Cirac, arXiv:cond-mat/0407066v1