Jul 2016
July 4-July 8 Bo Liu, July 11-July 15 Biao Huang, July 18-July 22 Haiyuan Zou, July 25-July 29 Ahmet Kel
July 22 arXiv:1607.06352 [pdf, ps, other] Density redistribution effects in fermionic optical lattices Medha Soni, Michele Dolfi, Matthias Troyer Comments: 10 pages, 16 pages Subjects: Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Computational Physics (physics.comp-ph) We simulate a one dimensional fermionic optical lattice to analyse heating due to non-adiabatic lattice loading. Our simulations reveal that, similar to the bosonic case, density redistribution effects are the major cause of heating in harmonic traps. We suggest protocols to modulate the local density distribution during the process of lattice loading, in order to reduce the excess energy. Our numerical results confirm that linear interpolation of the trapping potential and/or the interaction strength is an efficient method of doing so, bearing practical applications relevant to experiments. July 21 arXiv:1607.05908 [pdf, other] Probing an effective-range-induced super fermionic Tonks-Girardeau gas with ultracold atoms in one-dimensional harmonic traps Xiao-Long Chen, Xia-Ji Liu, Hui Hu Comments: 6 pages, 4 figures Subjects: Quantum Gases (cond-mat.quant-gas) We theoretically investigate an ultracold spin-polarized atomic Fermi gas with resonant odd-channel (p-wave) interactions trapped in one-dimensional harmonic traps. We solve the Yang-Yang thermodynamic equations based on the exact Bethe ansatz solution, and predict the finite-temperature density profile and breathing mode frequency, by using a local density approximation to take into account the harmonic trapping potential. The system features an exotic super fermionic Tonks-Girardeau (super-fTG) phase, due to the large effective range of the interatomic interactions. We explore the parameter space for such a fascinating super-fTG phase at finite temperature and provide smoking-gun signatures of its existence in both breathing mode frequencies and density profiles. Our results suggest that the super-fTG phase can be readily probed at temperature at about 0.1TF, where TF is the Fermi temperature. These results are to be confronted with future cold-atom experiments with 6Li and 40K atoms. July 20 arXiv:1607.05589 [pdf, ps, other] Atomic momentum patterns with narrower interval Baoguo Yang, Shengjie Jin, Xiangyu Dong, Zhe Liu, Lan Yin, Xiaoji Zhou Comments: 6 pages, 5 figures Subjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph) We studied the atomic momentum distribution for a superposition of Bloch states spreading in the lowest band of an optical lattice after the action of the standing wave pulse. By designing the imposing pulse on this superposed state, an atomic momentum pattern appears with narrower interval between the adjacent peaks that can be far less than the double recoil momentum. The patterns with narrower interval come from the superposition of the action of the designed pulse on many Bloch states with quasi-momenta over the first Brillouin zone, where for each quasi-momentum there is an interference among several lowest bands. Our experimental result of narrow interval peaks is consistent with the theoretical simulation. The patterns of multi modes with different quasi-momenta are helpful for precise measurement and atomic manipulation. July 19 arXiv:1607.04924 [pdf, ps, other] Type-II Weyl Points in Three-Dimensional Cold Atom Optical Lattices Yong Xu, Lu-Ming Duan Comments: 8 pages including supplementary materials. Comments are welcome Subjects: Quantum Gases (cond-mat.quant-gas) Weyl points can be divided into two classes: type-I and type-II, which are separated by a topological Lifshitz-type quantum phase transition. We propose a scheme to realize both type-I and type-II Weyl points in the single-particle spectra of ultracold atomic gases by introducing an experimentally feasible configuration for three-dimensional spin-orbit coupling. We find three Weyl points in the resultant Hamiltonian, one of which is a four-fold degenerate touching point consisting of two Weyl points carrying the same topological charge. All these Weyl points can transition from type-I to type-II via tuning of a convenient experimental knob. The proposed system provides an ideal platform to study different types of Weyl points and directly probe the Lifshitz phase transition between them. Jul 8 1. arXiv:1607.01930 [pdf, ps, other] Spin squeezing and Quantum Fisher Information in the Jaynes-Cummings Dicke Model Aranya B Bhattacherjee, Deepti Sharma We investigate spin squeezing (SS) and the quantum Fisher information (QFI) for the Jaynes-Cummings Dicke (JC-Dicke) model in a two component atomic Bose-Einstein condensate (BEC) inside an optical cavity. Analytical expressions for spin squeezing and the reciprocal of the quantum Fisher information per particle (RMQFI) are derived using the frozen spin approximation. It is shown that in the superradiant phase near the critical point, maximum squeezing and maximum quantum entanglement occurs. The present study is relevant to quantum information processing and precision spectroscopy. 2. arXiv:1607.01984 (cross-list from quant-ph) [pdf, other] Many-body decoherence dynamics and optimised operation of a single-photon switch Callum R. Murray, Alexey V. Gorshkov, Thomas Pohl We develop a theoretical framework to characterize the decoherence dynamics due to multi-photon scattering in an all-optical switch based on Rydberg atom induced nonlinearities. By incorporating the knowledge of this decoherence process into optimal photon storage and retrieval strategies, we establish optimised switching protocols for experimentally relevant conditions, and evaluate the corresponding limits in the achievable fidelities. Based on these results we work out a simplified description that reproduces recent experiments [arXiv:1511.09445] and provides a new interpretation in terms of many-body decoherence involving multiple incident photons and multiple gate excitations forming the switch. Aside from offering insights into the operational capacity of realistic photon switching capabilities, our work provides a complete description of spin wave decoherence in a Rydberg quantum optics setting, and has immediate relevance to a number of further applications employing photon storage in Rydberg media. Jul 7 1 arXiv:1607.01509 [pdf, other] Effective Field Theory for Few-Boson Systems Betzalel Bazak, Moti Eliyahu, Ubirajara van Kolck We study universal bosonic few-body systems within the framework of effective field theory at leading order (LO). We calculate binding energies of systems of up to six particles and the atom-dimer scattering length. Convergence to the limit of zero-range two- and three-body interactions is shown, indicating that no additional few-body interactions need to be introduced at LO. Generalizations of the Tjon line are constructed, showing correlations between few-body binding energies and the binding energy of the trimer, for a given dimer energy. As a specific example, we implement our theory for 4He atomic systems, and show that the results are in surprisingly good agreement with those of sophisticated 4He-4He potentials. Potential implications for the convergence of the EFT expansion are discussed. Jul 6 1. arXiv:1607.01328 [pdf, other] Interference of fractionalized quasiparticles in AIII topological insulators Carlos G. Velasco, Belén Paredes Fractionalization in one-dimensional topological insulators has not been yet directly observed. Moreover, novel symmetry classes of topological insulators like the AIII class lack experimental realization. Our work might open possibilities for both challenges. We propose a one-dimensional model realizing the AIII symmetry class which can be realized in current experiments with ultracold atomic gases. We further report on a remarkable property of topological edge modes: they are localized in momentum space. This opens a path for the direct observation of fractionalization by imaging the momentum distribution of the particles. Furthermore, we exploit the simultaneous sharp definition of the edge modes in position and momentum, to design a quench protocol in which the two halves of an atom move in opposite directions and interfere with each other, preserving their identity as 1/2-quasiparticles. Jul 5 1. arXiv:1607.00671 [pdf, other] Spectral properties and phase diagram of correlated lattice bosons in an optical cavity within the B-DMFT Jaromir Panas, Anna Kauch, Krzysztof Byczuk We use the Bose-Hubbard model with an effective infinite-range interaction to describe the correlated lattice bosons in an optical cavity. We study both static and spectral properties of such system within the bosonic dynamical mean-field theory (B-DMFT), which is the state of the art method for strongly correlated bosonic systems. Both similarities and differences are found and discussed between our results and these obtained within different theoretical methods and experiment. 2. arXiv:1607.00392 [pdf, other] Antiferromagnetic correlations in two-dimensional fermionic Mott-insulating and metallic phases J. H. Drewes, L. A. Miller, E. Cocchi, C. F. Chan, D. Pertot, F. Brennecke, M. Köhl Near zero temperature, quantum magnetism can non-trivially arise from short-range interactions, but the occurrence of magnetic order depends crucially on the interplay of interactions, lattice geometry, dimensionality and doping. Even though the consequences of this interplay are not yet fully understood, quantum magnetism is believed to be connected to a range of complex phenomena in the solid state, for example, in the context of high-Tc superconductivity and spin liquids in frustrated lattices. Ultracold atomic Fermi gases in optical lattices constitute an experimental system with unrivalled tunability and detection capabilities to explore quantum magnetism by analog quantum simulation. In this work, we study the emergence of antiferromagnetic correlations between ultracold fermionic atoms in two dimensions with decreasing temperature. We determine the magnetic susceptibility of the Hubbard model from simultaneous measurements of the in-situ density of both spin components. At half-filling and strong interactions our data approach the Heisenberg model of localized spins with antiferromagnetic correlations. Moreover, we observe the disappearance of magnetic correlations when the system is doped away from half-filling. Our observation of the dependence of quantum magnetism on doping paves the way for future studies on the emergence of pseudogap and pairing phenomena away from half-filling.
