Berlin 2014 – scientific programme

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A: Fachverband Atomphysik

A 29: Ultra-cold atoms, ions and BEC III (with Q)

A 29.3: Talk

Wednesday, March 19, 2014, 14:45–15:00, UDL HS3038

Bose-Einstein condensation of ultra-cold atoms in a frustrated, triangular optical lattice I. — •Ludwig Mathey¹, Robert Höppner¹, Peter Janzen¹, Julian Struck¹, Malte Weinberg¹, Christoph Ölschläger¹, Patrick Windpassinger¹, Juliette Simonet¹, Klaus Sengstock¹, Philipp Hauke², Andre Eckardt³, and Maciej Lewenstein⁴ — ¹Institut für Laserphysik and Zentrum für Optische Quantentechnologien, Universität Hamburg, Hamburg, Germany — ²IQOQI, Innsbruck, Austria — ³MPIKS, Dresden, Germany — ⁴ICFO and ICREA, Barcelona, Spain

We present a study of Bose-Einstein condensation of ultracold atoms in a triangular optical lattice. As demonstrated in Ref. [1], the tunneling energy between neighboring sites in an optical lattice can be controlled via lattice shaking to be negative or complex-valued. For negative, real-valued tunneling, the system condenses at one of two non-zero quasimomenta, corresponding to classical frustration. Tuning the tunneling energy to complex values corresponds to an artificial gauge field. We demonstrate that the nature of the condensation transition is modified due an additional chiral symmetry that is broken. Furthermore, the artificial gauge field acts as the conjugate external field to the chiral order parameter, which allows to map out magnetization curves of the chirality as a function of the article gauge field. In this talk we give analytical results on the nature of the phase transition, based on an expansion of the free energy in the interaction strength and on a renormalization group approach.

[1] J.Struck, et al., Nature Physics 9, 738 (2013)