Bulletin of the American Physical Society
46th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 60, Number 7
Monday–Friday, June 8–12, 2015; Columbus, Ohio
Session P6: Few and Many Body Physics in Lattice Bosons |
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Chair: Ben Olsen, Rice University Room: Delaware AB |
Thursday, June 11, 2015 2:00PM - 2:12PM |
P6.00001: Identifying the local conserved quantities in Many-Body-Localized matter David Pekker, Binbin Tian, Xiongji Yu, Bryan Clark, Vadim Oganesyan Typically, many-body systems with interactions tend to thermalize. However, adding sufficient disorder (or possibly via other mechanisms) one can induce many-body localization. The localization occurs by the spontaneous appearance of local conserved quantities. We describe how to identify these conserved quantities and explore their localization properties. We also comment on how these conserved quantities are reflected in cold atom experiments on localized matter. [Preview Abstract] |
Thursday, June 11, 2015 2:12PM - 2:24PM |
P6.00002: Dynamics at the Many-Body Localization Transition Lea Santos, Jonathan Torres-Herrera Studies about localization in interacting systems have recently boomed. The interest in the subject is motivated by indications of the existence of a many-body localization (MBL) phase and by advances in experiments with optical lattices, which may serve as testbeds for corroborating theoretical predictions. A paradigmatic system for these analysis is the one-dimensional isolated Heisenberg model with random magnetic fields. We study the dynamics of this system for initial states prepared with high energies. Our focus is on the probability for finding the initial state later in time, the so-called survival probability. Two distinct behaviors are identified before the saturation of the relaxation process. At short times, the decay is very fast, as typical of clean systems. It subsequently slows down and develops a powerlaw behavior with an exponent related with the multifractal structure of the eigenstates. The curve of the powerlaw exponent versus the disorder strength exhibits an inflection point that is associated with the metal-insulator transition point. [Preview Abstract] |
Thursday, June 11, 2015 2:24PM - 2:36PM |
P6.00003: Spectroscopy of the Mott insulator to Bose glass transition Carolyn Meldgin, Laura Wadleigh, Philip Russ, Brian DeMarco We present measurements probing the Mott insulator to Bose glass transition in three dimensions using spectroscopic techniques.~Ultracold 87Rb atoms trapped in a cubic optical lattice with independently controlled speckle disorder are used to realize the disordered Bose Hubbard model.~The Mott gap is measured in the clean lattice using Raman spectroscopy.~The addition of disorder causes a phase transition to the Bose glass state, which has a gapless excitation spectrum.~We use this signature to detect the phase transition as the ratio of Hubbard to tunneling energies is varied. [Preview Abstract] |
Thursday, June 11, 2015 2:36PM - 2:48PM |
P6.00004: Quantum Monte Carlo study of dipolar lattice bosons in the presence of random diagonal disorder Chao Zhang, Arghavan Safavi-Naini, Barbara Capogrosso-Sansone We report the results of our study of dipolar bosons in a two dimensional optical lattice in the presence of random diagonal disorders using Path Integral Quantum Monte Carlo simulations. We study the phase diagram at half filling which features three phases: superfluid, checkerboard solid and bose glass. We observe that, in contrast to the standard Bose-Hubbard model in presence of diagonal disorder, superfluidity is destroyed at considerable lower disorder strengths in favor of the Bose glass phase. Additionally we find that as the disorder strength increases, larger dipolar interaction is required in order to stabilize a checkerboard solid. [Preview Abstract] |
Thursday, June 11, 2015 2:48PM - 3:00PM |
P6.00005: Quantum Phase Transitions in mixtures of two Bosonic Species Barbara Capogrosso-Sansone, Fabio Lingua, Marco Guglielmino, Vittorio Penna We investigate the phase diagram of a two-component bosonic system in a square lattice by means of quantum Monte Carlo simulation. Depending on the interplay between inter- and intra-species interactions we show the existence of interesting quantum phases such as, among others, a demixed superfluid, a demixed Mott insulator, supercounterflow. [Preview Abstract] |
Thursday, June 11, 2015 3:00PM - 3:12PM |
P6.00006: An exact study of lattice bosons with coupling to an ohmic bath Arghavan Safavi-Naini, Barbara Capogrosso-Sansone, Ana Maria Rey In an open quantum system the presence of strong coupling between the system and its environment can result in significant changes in the behavior of the system. For instance, in the spin-boson model the coupling between the spin and a heat bath induces a quantum (quantum coherences) to classical (absence of quantum coherences) transition. While systems consisting of one or few spins have been studied in detail, less is known about equivalent many-body models. Using Path Integral Quantum Monte Carlo algorithm we are able to obtain the phase diagram of a system of two-dimensional lattice bosons with ohmic coupling to an external reservoir. We explore the role of the competition between many-body effects and dissipation in stabilizing novel quantum phases, analogous to the recently observed bose liquid phase in a dissipative one-dimensional chain of bosons [1].\\[4pt] [1] Zi Cai, Ulrich Schollw\"ock, and Lode Pollet, Phys. Rev. Lett. 113, 260403, (2014). [Preview Abstract] |
Thursday, June 11, 2015 3:12PM - 3:24PM |
P6.00007: Optical control of interaction strength in ultracold atomic gases with long lifetime Logan W. Clark, Yu-Ting Chen, Li-Chung Ha, Chen-Yu Xu, Cheng Chin The great utility of cold atom systems as quantum simulators arises from the experimenter's ability to continuously tune their Hamiltonians. Recently, there has been a great deal of interest in achieving optical control of Feshbach resonances, which would allow spatial modulation of the interaction strength at short length scales as well as fast temporal modulation. We report on a new scheme for optically controlling interaction strength using the effective magnetic field from a circularly polarized laser near a magnetic Feshbach resonance. This approach is technologically simple and overcomes the major shortcomings of existing methods; it provides access to a wide range of scattering lengths while maintaining long quantum gas lifetimes of many hundreds of milliseconds and avoiding incidental conservative forces on the atoms. We will report progress on experimentally realizing this scheme. [Preview Abstract] |
Thursday, June 11, 2015 3:24PM - 3:36PM |
P6.00008: Effective three-body interaction in an asymmetric double-well optical lattice Saurabh Paul, Eite Tiesinga We study ultracold atoms in a double-well optical lattice, with a view to creating an effective Hamiltonian that has large three-body interaction energy. The lattice has an asymmetric double-well geometry along the $x$ axis and single wells along the perpendicular axes. We obtain tunneling and two-body interaction energies using numerically constructed Wannier functions from an exact band structure calculation. This gives a Bose-Hubbard (BH) Hamiltonian spanning the lowest two bands along the $x$ axis, and the ground band along the perpendicular axes. We then obtain the many-particle (MP) states, $|\nu,N\rangle$, where $N(\le 3)$ is the particle number per site, and $\nu\in \{1,N+1\}$, by diagonalizing the on-site BH Hamiltonian in the particle number basis. Starting with the ground MP states, we show that tunneling is predominantly confined to the ground state in each $N$ sector. We thus create an effective Hamiltonian ($H_{\rm eff}$) in the ground MP states, and show that $H_{\rm eff}$ has large three-body interaction energy ($\Gamma_3$), comparable to or larger than the two-body term ($\Gamma_2$). The ratio $\Gamma_3/\Gamma_2$ can be tuned by changing the lattice parameters. We are now investigating the possibility of having unique many-body ground states for such systems. [Preview Abstract] |
Thursday, June 11, 2015 3:36PM - 3:48PM |
P6.00009: Three-body effective range and other properties for ultracold bosonic atoms near a three-body threshold Shina Tan, Kevin Driscoll, Shangguo Zhu The two-body scattering length and the effective range are important parameters for ultracold atoms. We introduce an analogous concept of \emph{three-body} effective range for three bosonic atoms near a three-body threshold. This will be useful for ultracold atoms near low-energy three-body resonances. It may also be relevant for certain nuclear systems near three-body resonances. For three bosons with large two-body scattering length, which display the Efimov effect, we derive \emph{analytical} results for the three-body effective range and the two-body and three-body contacts at the three-body threshold. [Preview Abstract] |
Thursday, June 11, 2015 3:48PM - 4:00PM |
P6.00010: Complex Networks and Quantum Phase Transitions David L. Vargas, Lincoln D. Carr Complex quantum dynamics will benefit from a new set of complex network theory tools going beyond quantum averages and correlations. As a first step towards quantifying quantum complexity, we show that these tools reproduce known quantum phase diagrams in transverse Ising and Bose-Hubbard models. Such models are realized in ultracold atoms and molecules in optical lattices. We present a finite size scaling analysis of the quantum mutual information networks present in the transverse Ising and Bose-Hubbard Hamiltonians. In the transverse Ising model the first derivative of network density, average disparity, and clustering coefficient with respect to the transverse field ($g$) are maximized at $g=1.002, 0.998, \textrm{ and } 1.002$ respectively as the number of sites in the lattice approaches infinity, and where the known critical point of the model occurs at $g_c=1$. In the Bose-Hubbard model we find the superfluid phase is characterized by a vanishing disparity, non-zero network density, and non-zero clustering coefficient as we extrapolate to an infinite number of lattice sites. Our analysis thus provides evidence that complex network analysis of quantum mutual information is sufficient to identify critical points and phase boundaries of distinct quantum many body models. [Preview Abstract] |
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