Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session L32: Invited Session: Magnetism in Quantum Gasses |
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Sponsoring Units: DAMOP Room: 708-712 |
Wednesday, March 5, 2014 8:00AM - 8:36AM |
L32.00001: In situ observation of strongly interacting ferromagnetic domains in a shaken optical lattice Invited Speaker: Cheng Chin . [Preview Abstract] |
Wednesday, March 5, 2014 8:36AM - 9:12AM |
L32.00002: Short-range Quantum Magnetism of Ultracold Fermions in an Optical Lattice Invited Speaker: Daniel Greif Quantum magnetism describes quantum many-body states with spins coupled by exchange interactions. At low temperatures this leads to short- and long-range magnetic ordering, which is for example the case in spin-liquids, valence-bond solids and antiferromagnets.\\ We report on the observation of magnetic spin correlations on neighboring sites of a Fermi gas in an optical lattice. The key to obtaining and detecting the short-range magnetic order is an entropy redistribution technique in a tunable-geometry optical lattice. We load a low-temperature two-component gas with repulsive interactions into either a dimerized or anisotropic simple cubic lattice. The correlations manifest as an excess number of singlets as compared to triplets consisting of two atoms with opposite spins. For the anisotropic lattice, we determine the transverse spin correlator from the singlet-triplet imbalance and observe antiferromagnetic correlations along one spatial axis. [Preview Abstract] |
Wednesday, March 5, 2014 9:12AM - 9:48AM |
L32.00003: Direct observation of interacting Magnons in optical lattices Invited Speaker: Christian Gross The quantum simulation of spinful many-body systems with ultracold atoms in optical lattices promises novel insight into fundamental aspects of magnetism. Here we report on the direct observation of coherent Magnon propagation after a local spin flip in the isotropic Heisenberg regime. Using our quantum gas microscope we track the position of the flipped spins during their propagation in the bath of opposite spins. When the local quantum quench is realized by flipping two adjacent spins the subsequent dynamics shows clear signatures of a stable Two-Magnon bound state propagating through the lattice. We extract the propagation velocity of the bound state and find slower dynamics due to the larger effective mass of the compound object. Tuning the system from the Mott insulating into the superfluid regime, we observe polaronic features in the non-equilibrium dynamics of a single spin impurity. Our results show the potential of local manipulation and detection for the study of correlations in magnetic quantum systems. [Preview Abstract] |
Wednesday, March 5, 2014 9:48AM - 10:24AM |
L32.00004: Realizing a Kondo-correlated state with ultracold atoms Invited Speaker: Johannes Bauer We propose a novel realization of Kondo physics with ultracold atomic gases. It is based on a Fermi sea of two different hyperfine states of one atom species forming bound states with a different species, which is spatially confined in a trapping potential. We show that different situations displaying Kondo physics can be realized when Feshbach resonances between the species are tuned by a magnetic field and the trapping frequency is varied. We illustrate that a mixture of ${}^{40}$K and ${}^{23}$Na atoms can be used to generate a Kondo correlated state and that momentum resolved radio frequency spectroscopy can provide unambiguous signatures of the formation of Kondo resonances at the Fermi energy. We discuss how tools of atomic physics can be used to investigate open questions for Kondo physics, such as the extension of the Kondo screening cloud. [Preview Abstract] |
Wednesday, March 5, 2014 10:24AM - 11:00AM |
L32.00005: Many-body quantum quench in an atomic one-dimensional Ising chain Invited Speaker: Hanns-Christoph Naegerl Quantum tunneling is one of the most fundamental processes in nature. Single particle hopping of ultracold atoms in optical lattices changes its character dramatically when the ensemble is prepared in strongly correlated quantum phases due to atom-atom interactions. Correlated hopping in a Mott-insulating chain of bosons that is tilted to the Mott gap has recently been employed to study long-range order in the 1D transvers Ising model [1,2]. We study correlated tunneling dynamics for an ensemble of tilted 1D Mott chains after a sudden quench to the vicinity of the Ising paramagnetic to antiferromagnetic phase transition point [3]. The quench results in coherent oscillations for the orientation of effective Ising spins, detected via oscillations in the number of doubly occupied lattice sites. We characterize the quench by varying the system parameters. We report significant modification of the tunneling rate induced by interactions and show clear evidence for collective effects in the oscillatory response. We observe higher-order many-body tunneling processes over up to five lattice sites when the tilt per site is tuned to integer fractions of the Mott gap. Second- and third-order tunneling shows up in the transient response after the quench, from which we extract the characteristic scaling in accordance with perturbation theory and numerical simulations. In a second set of experiments we study the response of an ensemble of 1D superfluids in the Bose-Hubbard regime when subject to a tilt [4]. For large values of the tilt, we observe interaction-induced coherent decay and matter-wave quantum phase revivals of the Bloch oscillating ensemble. We analyze the revival period dependence on interactions by means of a Feshbach resonance. When reducing the value of the tilt, we observe the disappearance of the quasi-periodic phase revival signature towards an irreversible decay of Bloch oscillations, indicating the transition from regular to quantum chaotic dynamics.\\[4pt] [1] J. Simon et al., Nature 472, 307 (2011)\\[0pt] [2] S. Sachdev et al., Phys. Rev. B 66, 075128 (2002)\\[0pt] [3] F. Meinert et al., Phys. Rev. Lett. 111, 053003 (2013)\\[0pt] [4] F. Meinert et al., arXiv:1309.4045 (2013) [Preview Abstract] |
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