tag:blogger.com,1999:blog-80283915617494654462016-09-29T00:52:52.720-07:00cond-mat.quant-gas - Quantum GasesSite for <a href="http://communitypeerreview.blogspot.com/">Community Peer Review</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.comBlogger2476125tag:blogger.com,1999:blog-8028391561749465446.post-44191585416512935022013-08-06T00:02:00.015-07:002013-08-06T00:02:21.475-07:001308.0603 (Johannes Bauer et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0603">Realizing a Kondo-correlated state with ultracold atoms</a> [<a href="http://arxiv.org/pdf/1308.0603">PDF</a>]</h2>Johannes Bauer, Christophe Salomon, Eugene Demler<a name='more'></a><blockquote class="abstract">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.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0603">http://arxiv.org/abs/1308.0603</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-14365488688377177362013-08-06T00:02:00.013-07:002013-08-06T00:02:20.493-07:001308.0681 (Krzysztof Jachymski et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0681">Analytical model of overlapping Feshbach resonances</a> [<a href="http://arxiv.org/pdf/1308.0681">PDF</a>]</h2>Krzysztof Jachymski, Paul S. Julienne<a name='more'></a><blockquote class="abstract">Feshbach resonances in ultracold collisions often result from an interplay between many collision channels. Simple two-channel models can be introduced to capture the basic features, but cannot fully reproduce the situation when several resonances from different closed channels contribute to the scattering process. Using the formalism of multichannel quantum defect theory we develop an analytical model of overlapping Feshbach resonances. We find a general formula for the variation of the scattering length with magnetic field in the vicinity of an arbitrary number of resonances, characterized by simple parameters. Our formula is in excellent agreement with numerical coupled channels calculations for several cases of overlapping resonances in the collisions of two $^7$Li atoms or two Cs atoms.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0681">http://arxiv.org/abs/1308.0681</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-74219683396181245232013-08-06T00:02:00.011-07:002013-08-06T00:02:19.610-07:001308.0750 (M. Burrello et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0750">Topological phase transitions driven by non-Abelian gauge potentials in<br /> optical square lattices</a> [<a href="http://arxiv.org/pdf/1308.0750">PDF</a>]</h2>M. Burrello, I. C. Fulga, E. Alba, L. Lepori, A. Trombettoni<a name='more'></a><blockquote class="abstract">We analyze a tight-binding model of ultracold fermions loaded in an optical square lattice and subjected to a synthetic non-Abelian gauge potential featuring both a magnetic field and a translational invariant SU(2) term. We consider in particular the effect of broken time-reversal symmetry and its role in driving non-trivial topological phase transitions. By varying the spin-orbit coupling parameters, we find both a semimetal/insulator phase transition and a topological phase transition between insulating phases with a different number of edge states. The spin is not a conserved quantity of the system and the topological phase transitions can be detected by analyzing its polarization in time of flight images, providing a clear diagnostics for the characterization of the topological phases through the partial entanglement between spin and lattice degrees of freedom.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0750">http://arxiv.org/abs/1308.0750</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-34788852030568638282013-08-06T00:02:00.009-07:002013-08-06T00:02:16.170-07:001308.0784 (A. M. Kamchatnov et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0784">Nonlinear waves of polarization in two-component Bose-Einstein<br /> condensates</a> [<a href="http://arxiv.org/pdf/1308.0784">PDF</a>]</h2>A. M. Kamchatnov, Y. V. Kartashov, P. -É. Larré, N. Pavloff<a name='more'></a><blockquote class="abstract">Waves with different symmetries exist in two-component Bose-Einstein condensates (BECs) whose dynamics is described by a system of coupled Gross-Pitaevskii (GP) equations. A first type of waves corresponds to excitations for which the motion of both components is locally in phase. In the second type of waves the two components have a counter-phase local motion. In the case of different values of inter- and intra-component interaction constants, the long wave-length behavior of these two modes corresponds to two types of sound with different velocities. In the limit of weak nonlinearity and small dispersion the first mode is described by the well-known Korteweg-de Vries (KdV) equation. We show that in the same limit the second mode can be described by the Gardner (modified KdV) equation, if the intra-component interaction constants have close enough values. This leads to a rich phenomenology of nonlinear excitations (solitons, kinks, algebraic solitons, breathers) which does not exist in the KdV description.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0784">http://arxiv.org/abs/1308.0784</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-33974177132116654222013-08-06T00:02:00.007-07:002013-08-06T00:02:15.224-07:001308.0852 (Davide Proment et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0852">Interaction and decay of Kelvin waves in the Gross-Pitaevskii model</a> [<a href="http://arxiv.org/pdf/1308.0852">PDF</a>]</h2>Davide Proment, Carlo F. Barenghi, Miguel Onorato<a name='more'></a><blockquote class="abstract">By solving numerically the governing Gross-Pitaevskii equation, we study the dynamics of Kelvin waves on a superfluid vortex. After determining the dispersion relation, we monitor the turbulent decay of Kelvin waves with energy initially concentrated at large length scales. At intermediate length scales, we find that the decay is consistent with scaling predictions of theoretical models. Finally we report the unexpected presence of large-length scale phonons in the system.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0852">http://arxiv.org/abs/1308.0852</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-76028821819813808192013-08-06T00:02:00.005-07:002013-08-06T00:02:14.356-07:001308.0922 (Luca Salasnich)<h2 class="title"><a href="http://arxiv.org/abs/1308.0922">Fermionic condensation in ultracold atoms, nuclear matter and neutron<br /> stars</a> [<a href="http://arxiv.org/pdf/1308.0922">PDF</a>]</h2>Luca Salasnich<a name='more'></a><blockquote class="abstract">We investigate the Bose-Einstein condensation of fermionic pairs in three different superfluid systems: ultracold and dilute atomic gases, bulk neutron matter, and neutron stars. In the case of dilute gases made of fermionic atoms the average distance between atoms is much larger than the effective radius of the inter-atomic potential. Here the condensation of fermionic pairs is analyzed as a function of the s-wave scattering length, which can be tuned in experiments by using the technique of Feshbach resonances from a small and negative value (corresponding to the Bardeen-Cooper-Schrieffer (BCS) regime of Cooper Fermi pairs) to a small and positive value (corresponding to the regime of the Bose-Einstein condensate (BEC) of molecular dimers), crossing the unitarity regime where the scattering length diverges. In the case of bulk neutron matter the s-wave scattering length of neutron-neutron potential is negative but fixed, and the condensate fraction of neutron-neutron pairs is studied as a function of the total neutron density. Our results clearly show a BCS-quasiunitary-BCS crossover by increasing the neutron density. Finally, in the case of neutron stars, where again the neutron-neutron scattering length is negative and fixed, we determine the condensate fraction as a function of the distance from the center of the neutron star, finding that the maximum condensate fraction appears in the crust of the neutron star.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0922">http://arxiv.org/abs/1308.0922</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-64836231787871425142013-08-06T00:02:00.003-07:002013-08-06T00:02:13.415-07:001308.0939 (S. Ramanan et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0939">BEC-BCS Crossover in Neutron Matter with Renormalization Group based<br /> Effective Interactions</a> [<a href="http://arxiv.org/pdf/1308.0939">PDF</a>]</h2>S. Ramanan, M. Urban<a name='more'></a><blockquote class="abstract">We study pure neutron matter in the BEC-BCS crossover regime using renormalization group based low-momentum interactions within the Nozi\`eres-Schmitt-Rink framework. This is an attempt to go beyond the mean field description for low-density matter. We work in the basis of so-called Weinberg eigenvectors where the operator $G_0V$ is diagonal, which proves to be an excellent choice that allows one to use non-local interactions in a very convenient way. We study the importance of correlations as a function of density. We notice that there is a significant reduction of the BCS critical temperature at low-densities as the neutron matter approaches the unitary limit.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0939">http://arxiv.org/abs/1308.0939</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-86745015801902505172013-08-06T00:02:00.001-07:002013-08-06T00:02:12.298-07:001308.1032 (F. M. Marchetti et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.1032">Collective pairing of resonantly coupled microcavity polaritons</a> [<a href="http://arxiv.org/pdf/1308.1032">PDF</a>]</h2>F. M. Marchetti, J. Keeling<a name='more'></a><blockquote class="abstract">We consider the collective behavior of microcavity polaritons tuned near a bipolariton Feshbach resonance. We show that as well as the regular polariton superfluid phase a "molecular" superfluid phase exists, with (quasi-)long-range order only for pairs of polaritons. We describe the experimental signatures of this phase. Using variational approaches we find the phase diagram (critical temperature, density and exciton-photon detuning). Unlike ultracold atoms, the molecular superfluid phase is not inherently unstable, and our phase diagram suggests it is attainable in current experiments.</blockquote>View original: <a href="http://arxiv.org/abs/1308.1032">http://arxiv.org/abs/1308.1032</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-85395670211268207492013-08-05T00:01:00.009-07:002013-08-05T00:01:41.387-07:001308.0453 (Alexey N. Pyrkov et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0453">Entanglement generation in quantum networks of Bose-Einstein condensates</a> [<a href="http://arxiv.org/pdf/1308.0453">PDF</a>]</h2>Alexey N. Pyrkov, Tim Byrnes<a name='more'></a><blockquote class="abstract">Two component (spinor) Bose-Einstein condensates (BECs) are considered as the nodes of an interconnected quantum network. Unlike standard single-system qubits, in a BEC the quantum information is duplicated in a large number of identical bosonic particles, thus can be considered to be a "macroscopic" qubit. One of the difficulties with such a system is how to effectively interact such qubits together in order to transfer quantum information and create entanglement. Here we propose a scheme of cavities containing spinor BECs coupled by optical fiber in order to achieve this task. We discuss entanglement generation and quantum state transfer between nodes using such macroscopic BEC qubits.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0453">http://arxiv.org/abs/1308.0453</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-89149594715876867242013-08-05T00:01:00.007-07:002013-08-05T00:01:40.466-07:001308.0468 (R. Kishor Kumar et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0468">Vortical and fundamental solitons in dipolar Bose-Einstein condensates<br /> trapped in isotropic and anisotropic nonlinear potentials</a> [<a href="http://arxiv.org/pdf/1308.0468">PDF</a>]</h2>R. Kishor Kumar, P. Muruganandam, B. A. Malomed<a name='more'></a><blockquote class="abstract">We predict the existence of stable fundamental and vortical bright solitons in dipolar Bose-Einstein condensates (BECs) with repulsive dipole-dipole interactions (DDI). The condensate is trapped in the 2D plane with the help of the repulsive contact interactions whose local strength grows $\sim r^{4}$ from the center to periphery, while dipoles are oriented perpendicular to the self-trapping plane. The confinement in the perpendicular direction is provided by the usual harmonic-oscillator potential. The objective is to extend the recently induced concept of the self-trapping of bright solitons and solitary vortices in the pseudopotential, which is induced by the repulsive local nonlinearity with the strength growing from the center to periphery, to the case when the trapping mechanism competes with the long-range repulsive DDI. Another objective is to extend the analysis for elliptic vortices and solitons in an anisotropic nonlinear pseudopotential. Using the variational approximation (VA) and numerical simulations, we construct families of self-trapped modes with vorticities $\ell =0$ (fundamental solitons), $\ell =1$, and $\ell =2$. The fundamental solitons and vortices with $\ell =1$ exist up to respective critical values of the eccentricity of the anisotropic pseudopotential, being stable in the entire existence regions. The vortices with $\ell =2$ are stable solely in the isotropic model.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0468">http://arxiv.org/abs/1308.0468</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-22122889306302814872013-08-05T00:01:00.005-07:002013-08-05T00:01:39.842-07:001308.0487 (Vivek M. Vyas et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0487">On Berezinskii-Kosterlitz-Thouless phase transition and universal<br /> breathing mode in two dimensional photon gas</a> [<a href="http://arxiv.org/pdf/1308.0487">PDF</a>]</h2>Vivek M. Vyas, Prasanta K. Panigrahi, J. Banerji<a name='more'></a><blockquote class="abstract">A system of two dimensional photon gas has recently been realized experimentally. It is pointed out that this setup can be used to observe a universal breathing mode of photon gas. It is shown that a modification in the experimental setup would open up a possibility of observing the Berezinskii-Kosterlitz-Thouless (BKT) phase transition in such a system. It is shown that the universal jump in the superfluid density of light in the output channel can be used as an unambiguous signature for the experimental verification of the BKT transition.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0487">http://arxiv.org/abs/1308.0487</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-50082075534625716342013-08-05T00:01:00.003-07:002013-08-05T00:01:38.841-07:001308.0528 (K. Stannigel et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0528">Constrained dynamics via the Zeno effect in quantum simulation:<br /> Implementing non-Abelian lattice gauge theories with cold atoms</a> [<a href="http://arxiv.org/pdf/1308.0528">PDF</a>]</h2>K. Stannigel, P. Hauke, D. Marcos, M. Hafezi, S. Diehl, M. Dalmonte, P. Zoller<a name='more'></a><blockquote class="abstract">We show how engineered classical noise can be used to generate constrained Hamiltonian dynamics in atomic quantum simulators of many-body systems, taking advantage of the continuous Zeno effect. After discussing the general theoretical framework, we focus on applications in the context of lattice gauge theories, where imposing exotic, quasi-local constraints is usually challenging. We demonstrate the effectiveness of the scheme for both Abelian and non-Abelian gauge theories, and discuss how engineering dissipative constraints substitutes complicated, non-local interaction patterns by global coupling to laser fields.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0528">http://arxiv.org/abs/1308.0528</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-40647768153072200472013-08-05T00:01:00.001-07:002013-08-05T00:01:37.749-07:001308.0567 (Przemyslaw Bienias et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0567">Ground state of a two component dipolar Fermi gas in a harmonic<br /> potential</a> [<a href="http://arxiv.org/pdf/1308.0567">PDF</a>]</h2>Przemyslaw Bienias, Krzysztof Pawlowski, Tilman Pfau, Kazimierz Rzazewski<a name='more'></a><blockquote class="abstract">Interacting two component Fermi gases are at the heart of our understanding of macroscopic quantum phenomena like superconductivity. Changing nature of the interaction is expected to head to novel quantum phases. Here we study the ground state of a two component fermionic gas in a harmonic potential with dipolar and contact interactions. Using a variational Wigner function we present the phase diagram of the system with equal but opposite values of the magnetic moment. We identify the second order phase transition from paramagnetic to ferronematic phase. Moreover, we show the impact of the experimentally relevant magnetic field on the stability and the magnetization of the system. We also investigate a two component Fermi gas with large but almost equal values of the magnetic moment to study how the interplay between contact and dipolar interactions affects the stability properties of the mixture. To be specific we discuss experimentally relevant parameters for ultracold $^{161}$Dy.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0567">http://arxiv.org/abs/1308.0567</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-76703354370703368342013-08-04T00:02:00.013-07:002013-08-04T00:02:47.264-07:000912.5379 (Bo Xiong et al.)<h2 class="title"><a href="http://arxiv.org/abs/0912.5379">Distortion of Interference Fringes and the Resulting Vortex Production<br /> of Merging Bose-Einstein Condensates</a> [<a href="http://arxiv.org/pdf/0912.5379">PDF</a>]</h2>Bo Xiong, Tao Yang, Keith A. Benedict<a name='more'></a><blockquote class="abstract">We investigate the effects of interatomic interactions and expansion on the distortion of interference fringes of a pair of initially well-separated, but coherent, condensate clouds trapped in a harmonic trap. The distortion of interference fringes, which can lead to the spontaneous formation of vortices in the atom clouds, depends crucially on two relevant parameters: the center-of-mass velocity and peak density of the initial state. We identify three qualitatively distinct regimes for the interfering condensates: collision, expansion, and merging, by the spatial and temporal features of the fringe spacings. Using a comprehensive set of numerical simulations based on the Gross-Pitaevskii equation, we specify the cross-overs between these regimes and propose the optimal the system parameters required for dynamical instabilities and vortex creation.</blockquote>View original: <a href="http://arxiv.org/abs/0912.5379">http://arxiv.org/abs/0912.5379</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-5320901849968564912013-08-04T00:02:00.011-07:002013-08-04T00:02:42.389-07:001308.0058 (Roger R. Sakhel et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0058">Momentum density and phase maps of a two-dimensional trapped<br /> Bose-Einstein condensate excited by a red laser</a> [<a href="http://arxiv.org/pdf/1308.0058">PDF</a>]</h2>Roger R. Sakhel, Asaad R. Sakhel, Humam B. Ghassib<a name='more'></a><blockquote class="abstract">We investigate numerically the momentum density and phase maps $-$in coordinate and momentum space$-$ of a two dimensional Bose-Einstein condensate (BEC) excited by a moving red-detuned laser potential. The BEC is confined in a harmonic trap cutoff by hard walls. The system and excitation scheme are as in our previous work (Roger R. Sakhel {\it et al.} to appear in J. Low Temp. Phys. (2013)); but with twice the number of particles and interaction strength. We solve the time-dependent Gross-Pitaevskii equation numerically using the split-step Crank-Nicolson method in real time. It is demonstrated that the red-detuned laser has a phase-imprinting effect like a repulsive potential barrier. Signatures of excitations are extracted from the dynamics of the momentum densities and phase maps. Further, a new phase is defined in momentum space, which is used to reveal excitations. Therefore, phase maps in coordinate space and momentum space are compared for different BEC evolution times. We argue, that this momentum-space phase is especially important with regard to the studies of BEC momentum distributions. In addition, this work presents a new method of BEC interferometry and should contribute to the ongoing research in that field. One of our significant findings is the presence of substantial differences betwteen the momentum density obtained by a Fourier transform (FT) of the spatial density distribution and the one obtained from the modulus of the wavefunction in momentum space; the latter is obtained by a FT of the spatial wavefunction.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0058">http://arxiv.org/abs/1308.0058</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-66430710613429225572013-08-04T00:02:00.009-07:002013-08-04T00:02:40.812-07:001308.0205 (M. M. Valado et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0205">Rydberg tomography of an ultra-cold atomic cloud</a> [<a href="http://arxiv.org/pdf/1308.0205">PDF</a>]</h2>M. M. Valado, N. Malossi, S. Scotto, D. Ciampini, E. Arimondo, O. Morsch<a name='more'></a><blockquote class="abstract">One of the most striking features of the strong interactions between Rydberg atoms is the dipole blockade effect, which allows only a single excitation to the Rydberg state within the volume of the blockade sphere. Here we present a method that spatially visualizes this phenomenon in an inhomogeneous gas of ultra-cold rubidium atoms. In our experiment we scan the position of one of the excitation lasers across the cold cloud and determine the number of Rydberg excitations detected as a function of position. Comparing this distribution to the one obtained for the number of ions created by a two-photon ionization process via the intermediate 5P level, we demonstrate that the blockade effect modifies the width of the Rydberg excitation profile. Furthermore, we study the dynamics of the Rydberg excitation and find that the timescale for the excitation depends on the atomic density at the beam position.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0205">http://arxiv.org/abs/1308.0205</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-47769758892336971782013-08-04T00:02:00.007-07:002013-08-04T00:02:39.992-07:001308.0264 (H. Schempp et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0264">Full counting statistics of laser excited Rydberg aggregates in a<br /> one-dimensional geometry</a> [<a href="http://arxiv.org/pdf/1308.0264">PDF</a>]</h2>H. Schempp, G. Günter, M. Robert-de-Saint-Vincent, C. S. Hofmann, D. Breyel, A. Komnik, D. W. Schönleber, M. Gärttner, J. Evers, S. Whitlock, M. Weidemüller<a name='more'></a><blockquote class="abstract">We experimentally study the full counting statistics of few-body Rydberg aggregates excited from a quasi-one-dimensional Rydberg gas. We measure asymmetric excitation spectra and increased second and third order statistical moments of the Rydberg number distribution, from which we determine the average aggregate size. Direct comparisons with numerical simulations reveal the presence of liquid-like spatial correlations, and indicate sequential growth of the aggregates around an initial grain. These findings demonstrate the importance of dissipative effects in strongly correlated Rydberg gases and introduce a way to study spatio-temporal correlations in strongly-interacting many-body quantum systems without imaging.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0264">http://arxiv.org/abs/1308.0264</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-22883394884376616122013-08-04T00:02:00.005-07:002013-08-04T00:02:35.113-07:001308.0280 (D. Neilson et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0280">Excitonic Superfluidity and Screening in Electron-Hole Bilayer Systems</a> [<a href="http://arxiv.org/pdf/1308.0280">PDF</a>]</h2>D. Neilson, A. Perali, A. R. Hamilton<a name='more'></a><blockquote class="abstract">We address the controversy on the effectiveness of screening and the importance of vertex corrections in the long range interactions that generate superfluid pairing in electron-hole bilayer systems in graphene and GaAs. We assess proposed mean-field approximations that treat screening very differently and which neglect vertex corrections, by comparing their predictions for the superfluid condensate fraction with recent Diffusion Quantum Monte Carlo results. We find that screening in the superfluid state is the best mean-field approximation and that vertex corrections are negligible.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0280">http://arxiv.org/abs/1308.0280</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-16731834444636014952013-08-04T00:02:00.003-07:002013-08-04T00:02:34.320-07:001308.0281 (Lih-King Lim et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0281">Mass and chirality inversion of a Dirac cone pair in Stückelberg<br /> interferometry</a> [<a href="http://arxiv.org/pdf/1308.0281">PDF</a>]</h2>Lih-King Lim, Jean-Noël Fuchs, Gilles Montambaux<a name='more'></a><blockquote class="abstract">The aim of the present work is to show that a St\"{u}ckelberg interferometer made of two massive Dirac cones can reveal information on band eigenstates such as the chirality and mass sign of the cones. For a given spectrum featuring two gapped cones, we propose several low-energy Hamiltonians differing by their eigenstates properties. The corresponding inter-band transition probability is affected by such differences in its interference fringes being shifted by a new phase of geometrical origin. This phase can be a useful bulk probe for cold atoms in topological optical lattices.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0281">http://arxiv.org/abs/1308.0281</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-57873644608266764042013-08-04T00:02:00.001-07:002013-08-04T00:02:30.409-07:001308.0321 (M. Aidelsburger et al.)<h2 class="title"><a href="http://arxiv.org/abs/1308.0321">Realization of the Hofstadter Hamiltonian with ultracold atoms in<br /> optical lattices</a> [<a href="http://arxiv.org/pdf/1308.0321">PDF</a>]</h2>M. Aidelsburger, M. Atala, M. Lohse, J. T. Barreiro, B. Paredes, I. Bloch<a name='more'></a><blockquote class="abstract">We demonstrate the experimental implementation of an optical lattice that allows for the generation of large homogeneous and tunable artificial magnetic fields with ultracold atoms. Using laser-assisted tunneling in a tilted optical potential we engineer spatially dependent complex tunneling amplitudes. Thereby atoms hopping in the lattice accumulate a phase shift equivalent to the Aharonov-Bohm phase of charged particles in a magnetic field. We determine the local distribution of fluxes through the observation of cyclotron orbits of the atoms on lattice plaquettes, showing that the system is described by the Hofstadter model. Furthermore, we show that for two atomic spin states with opposite magnetic moments, our system naturally realizes the time-reversal symmetric Hamiltonian underlying the quantum spin Hall effect, i.e., two different spin components experience opposite directions of the magnetic field.</blockquote>View original: <a href="http://arxiv.org/abs/1308.0321">http://arxiv.org/abs/1308.0321</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-66447310941308049492013-08-01T00:31:00.015-07:002013-08-01T00:31:54.109-07:001307.8126 (K. Saha et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8126">Phases and collective modes of Rydberg atoms in an optical lattice</a> [<a href="http://arxiv.org/pdf/1307.8126">PDF</a>]</h2>K. Saha, S. Sinha, K. Sengupta<a name='more'></a><blockquote class="abstract">We chart out the possible phases of laser driven Rydberg atoms in the presence of a hypercubic optical lattice. We define a pseudospin degree of freedom whose up(down) components correspond to the excited(ground) states of the Rydberg atoms and use them to demonstrate the realization of a canted Ising antiferromagnetic (CIAF) Mott phase of the atoms in these systems. We also show that on lowering the lattice depth, the quantum melting of the CIAF and density-wave (DW) Mott states (which are also realized in these systems) leads to supersolid (SS) phases of the atoms. We provide analytical expressions for the phase boundaries and collective excitations of these phases in the hardcore limit within mean-field theory and discuss possible experiments to test our theory.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8126">http://arxiv.org/abs/1307.8126</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-68871287696253044412013-08-01T00:31:00.013-07:002013-08-01T00:31:53.146-07:001307.8129 (Mikhail Lemeshko)<h2 class="title"><a href="http://arxiv.org/abs/1307.8129">Manipulating scattering of ultracold atoms with light-induced<br /> dissipation</a> [<a href="http://arxiv.org/pdf/1307.8129">PDF</a>]</h2>Mikhail Lemeshko<a name='more'></a><blockquote class="abstract">Recently it has been shown that pairs of atoms can form metastable bonds due to non-conservative forces induced by dissipation [Lemeshko&Weimer, Nature Comm. 4, 2230 (2013)]. Here we study the dynamics of interaction-induced coherent population trapping - the process responsible for the formation of dissipatively bound molecules. We derive the effective dissipative potentials induced between ultracold atoms by laser light, and study the time evolution of the scattering states. We demonstrate that binding occurs on short timescales of ~10 microseconds, even if the initial kinetic energy of the atoms significantly exceeds the depth of the dissipative potential. Dissipatively-bound molecules with preordained bond lengths and vibrational wavefunctions can be created and detected in current experiments with ultracold atoms.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8129">http://arxiv.org/abs/1307.8129</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-90309823474187065652013-08-01T00:31:00.011-07:002013-08-01T00:31:52.320-07:001307.8231 (Supratik Sarkar et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8231">Nonlocality induced spread of phonon spectrum in the Gross-Pitaevskii<br /> model of BEC</a> [<a href="http://arxiv.org/pdf/1307.8231">PDF</a>]</h2>Supratik Sarkar, A. Bhattacharyay<a name='more'></a><blockquote class="abstract">We add a minimal correction term to the local Gross-Pitaevskii equation to represent non-locality. Within the scope of Born approximation, we show that, the $\delta$-correlated interactions of the local Gross-Pitaevskii equation captures qualitatively correct features of the nonlocal scenario even when the s-wave scattering length is as large as the average separation of the particles in the dilute gas. We show that, the effective minimal nonlocality enhances the effective mass of particles in the kinetic energy part of the spectrum causing a spread of the phonon part of the Bogoliubov spectrum.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8231">http://arxiv.org/abs/1307.8231</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-2873742479727990422013-08-01T00:31:00.009-07:002013-08-01T00:31:51.284-07:001307.8282 (V. Bolpasi et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8282">An ultra-bright atom laser</a> [<a href="http://arxiv.org/pdf/1307.8282">PDF</a>]</h2>V. Bolpasi, N. K. Efremidis, M. J. Morrissey, P. Condylis, D. Sahagun, M. Baker, W. von Klitzing<a name='more'></a><blockquote class="abstract">We present a novel, ultra-bright atom-laser and ultra-cold thermal atom beam. Using rf-radiation we strongly couple the magnetic hyperfine levels of 87Rb atoms in a magnetically trapped Bose-Einstein condensate. At low rf-frequencies gravity opens a small hole in the trapping potenital and a well collimated, extremely bright atom laser emerges from just below the condensate. As opposed to traditional atom lasers based on weak coupling, this technique allows us to outcouple atoms at an arbitrarily large rate. We demonstrate an increase in flux per atom in the BEC by a factor of sixteen compared to the brightest quasi-continuous atom laser. Furthermore, we produce by two orders of magnitude the coldest thermal atom beam to date (200 nK).</blockquote>View original: <a href="http://arxiv.org/abs/1307.8282">http://arxiv.org/abs/1307.8282</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0tag:blogger.com,1999:blog-8028391561749465446.post-69077612806272695432013-08-01T00:31:00.007-07:002013-08-01T00:31:50.348-07:001307.8349 (A. Celi et al.)<h2 class="title"><a href="http://arxiv.org/abs/1307.8349">Synthetic gauge fields in synthetic dimensions</a> [<a href="http://arxiv.org/pdf/1307.8349">PDF</a>]</h2>A. Celi, P. Massignan, J. Ruseckas, N. Goldman, I. B. Spielman, G. Juzeliunas, M. Lewenstein<a name='more'></a><blockquote class="abstract">We propose a simple scheme to generate a cold-atom lattice pierced by a uniform magnetic field. Our method is based on a one-dimensional optical lattice extended by a synthetic dimension provided by the internal atomic degrees of freedom, effectively yielding a synthetic 2D lattice. Suitable laser-coupling of different internal states leads to a uniform magnetic flux within the 2D lattice. We show that this setup allows to study the main features of magnetic lattice systems, such as the fractal Hofstadter butterfly spectrum and the chiral edge states of the associated Chern insulating phases.</blockquote>View original: <a href="http://arxiv.org/abs/1307.8349">http://arxiv.org/abs/1307.8349</a>C.P.R.http://www.blogger.com/profile/13598012384534951656noreply@blogger.com0