Stuttgart 2012 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 27: Quantengase: Optische Gitter 2

Q 27.5: Vortrag

Dienstag, 13. März 2012, 15:00–15:15, V53.01

Tunable frustration as a discriminator of antiferromagnetic signatures in cold atoms — •Nils Blümer and Elena Gorelik — Institut für Physik, Universität Mainz

Very recently, it has become possible to continuously tune optical lattices from square to triangular (or honeycomb) topology [1]. We propose, based on quantum Monte Carlo simulations within dynamical mean-field theory (DMFT), that the variable frustration introduced by diagonal hopping t′ can help to establish unambiguous signatures of antiferromagnetism, even in the presence of large experimental errors. A concomitant change of energy scales can be avoided by adding suitable inter-plane hopping, effectively allowing for pure tuning of frustration at constant effective coordination number. We show that the recently suggested signature [2] of antiferromagnetic (AF) correlations, an enhanced double occupancy at strong coupling, is suppressed (proportional to t′²) even before the AF order breaks down; in contrast, nonmagnetic phases are unaffected. We expect that this DMFT scenario survives the suppression of long-range order (with dimensionality 2≤ d≤ 3) by spatial fluctuations; in experiments, the dependence of D on t′ then reveals local AF order for entropy s≲ log(2) per particle.

[1] L. Tarruell, D. Greif, T. Uehlinger, G. Jotzu, and T. Esslinger, arXiv:1111.5020.

[2] E. V. Gorelik, I. Titvinidze, W. Hofstetter, M. Snoek, and N. Blümer, Phys. Rev. Lett. 105, 065301 (2010).

[3] E. V. Gorelik, D. Rost, T. Paiva, R. Scalettar, A. Klümper, and N. Blümer, arXiv:1105.3356.