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Wolfgang Ketterle - One of the best experts on this subject based on the ideXlab platform.
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observation of bose Einstein Condensation in a strong synthetic magnetic field
Nature Physics, 2015Co-Authors: Colin Kennedy, William Cody Burton, Woo Chang Chung, Wolfgang KetterleAbstract:Extensions of Berry’s phase and the quantum Hall effect have led to the discovery of new states of matter with topological properties. Traditionally, this has been achieved using magnetic fields or spin–orbit interactions, which couple only to charged particles. For neutral ultracold atoms, synthetic magnetic fields have been created that are strong enough to realize the Harper–Hofstadter model. We report the first observation of Bose–Einstein Condensation in this system and study the Harper–Hofstadter Hamiltonian with one-half flux quantum per lattice unit cell. The diffraction pattern of the superfluid state directly shows the momentum distribution of the wavefunction, which is gauge-dependent. It reveals both the reduced symmetry of the vector potential and the twofold degeneracy of the ground state. We explore an adiabatic many-body state preparation protocol via the Mott insulating phase and observe the superfluid ground state in a three-dimensional lattice with strong interactions. The Bose–Einstein Condensation of ultracold atoms in a strong synthetic magnetic field in a cubic lattice realizes the Harper–Hofstadter model used in the study of topological states of matter.
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Observation of Bose-Einstein Condensation of molecules.
Physical review letters, 2003Co-Authors: Martin Zwierlein, Claudiu A. Stan, Christian H. Schunck, S. M. F. Raupach, Subhadeep Gupta, Zoran Hadzibabic, Wolfgang KetterleAbstract:We have observed Bose-Einstein Condensation of molecules. When a spin mixture of fermionic $^{6}\mathrm{L}\mathrm{i}$ atoms was evaporatively cooled in an optical dipole trap near a Feshbach resonance, the atomic gas was converted into $^{6}\mathrm{L}\mathrm{i}_{2}$ molecules. Below 600 nK, a Bose-Einstein condensate of up to 900 000 molecules was identified by the sudden onset of a bimodal density distribution. This condensate realizes the limit of tightly bound fermion pairs in the crossover between BCS superfluidity and Bose-Einstein Condensation.
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Bose-Einstein Condensation of atomic gases.
Nature, 2002Co-Authors: James R. Anglin, Wolfgang KetterleAbstract:The early experiments on Bose-Einstein Condensation in dilute atomic gases accomplished three long-standing goals. First, cooling of neutral atoms into their motional ground state, thus subjecting them to ultimate control, limited only by Heisenberg's uncertainty relation. Second, creation of a coherent sample of atoms, in which all occupy the same quantum state, and the realization of atom lasers - devices that output coherent matter waves. And third, creation of a gaseous quantum fluid, with properties that are different from the quantum liquids helium-3 and helium-4. The field of Bose-Einstein Condensation of atomic gases has continued to progress rapidly, driven by the combination of new experimental techniques and theoretical advances. The family of quantum-degenerate gases has grown, and now includes metastable and fermionic atoms. Condensates have become an ultralow-temperature laboratory for atom optics, collisional physics and many-body physics, encompassing phonons, superfluidity, quantized vortices, Josephson junctions and quantum phase transitions.
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bose Einstein Condensation
Physics World, 1997Co-Authors: Christopher Townsend, Wolfgang Ketterle, Sandro StringariAbstract:In 1924 the Indian physicist Satyendra Nath Bose sent Einstein a paper in which he derived the Planck law for black-body radiation by treating the photons as a gas of identical particles. Einstein generalized Bose's theory to an ideal gas of identical atoms or molecules for which the number of particles is conserved and, in the same year, predicted that at sufficiently low temperatures the particles would become locked together in the lowest quantum state of the system. We now know that this phenomenon, called Bose-Einstein Condensation (BEC), only happens for "bosons" – particles with a total spin that is an integer multiple of h, the Planck constant divided by 2π.
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bose Einstein Condensation in a tightly confining dc magnetic trap
Physical Review Letters, 1996Co-Authors: M O Mewes, M R Andrews, N J Van Druten, D M Kurn, Dallin Durfee, Wolfgang KetterleAbstract:Bose-Einstein Condensation of sodium atoms has been observed in a novel ``cloverleaf'' trap. This trap combines tight confinement with excellent optical access, using only dc electromagnets. Evaporative cooling in this trap produced condensates of $5\ifmmode\times\else\texttimes\fi{}{10}^{6}$ atoms, a tenfold improvement over previous results. We measured the condensate fraction and the repulsive mean-field energy, finding agreement with theoretical predictions.
A N Slavin - One of the best experts on this subject based on the ideXlab platform.
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bose Einstein Condensation in an ultra hot gas of pumped magnons
Nature Communications, 2014Co-Authors: A A Serga, Dmytro A. Bozhko, Vasil Tiberkevich, C W Sandweg, V I Vasyuchka, A V Chumak, Timo Neumann, Bjorn Obry, Gennadii A Melkov, A N SlavinAbstract:Bose-Einstein Condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein Condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.
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thermalization of a parametrically driven magnon gas leading to bose Einstein Condensation
Physical Review Letters, 2007Co-Authors: V E Demidov, S O Demokritov, O Dzyapko, G A Melkov, A N SlavinAbstract:The thermalization of parametrically pumped magnons caused by nonlinear multimagnon scattering processes and leading to the magnon Bose-Einstein Condensation is investigated experimentally with high temporal resolution. The threshold pumping power necessary for the thermalization is determined. For pumping powers above this threshold the thermalization time has been found to decrease rapidly with power reaching the value down to 50 ns, which is much smaller than the magnon lifetime.
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bose Einstein Condensation of quasi equilibrium magnons at room temperature under pumping
Nature, 2006Co-Authors: S O Demokritov, V E Demidov, O Dzyapko, G A Melkov, A A Serga, B Hillebrands, A N SlavinAbstract:Bose–Einstein Condensation (BEC), a form of matter first postulated in 1924, has famously been demonstrated in dilute atomic gases at ultra-low temperatures. Much effort is now being devoted to exploring solid-state systems in which BEC can occur. In theory semiconductor microcavities, where photons are confined and coupled to electronic excitations leading to the creation of polaritons, could allow BEC at standard cryogenic temperatures. Kasprzak et al. now present experiments in which polaritons are excited in such a microcavity. Above a critical polariton density, spontaneous onset of a macroscopic quantum phase occurs, indicating a solid-state BEC. BEC should also be possible at higher temperatures if coupling of light with solid excitations is sufficiently strong. Demokritov et al. have achieved just that, BEC at room temperature in a gas of magnons, which are a type of magnetic excitation. Bose–Einstein Condensation, the formation of a collective quantum state of identical particles, called bosons, is observed at room temperature in a gas of magnons, which are a type of magnetic excitation. Bose–Einstein Condensation1,2 is one of the most fascinating phenomena predicted by quantum mechanics. It involves the formation of a collective quantum state composed of identical particles with integer angular momentum (bosons), if the particle density exceeds a critical value. To achieve Bose–Einstein Condensation, one can either decrease the temperature or increase the density of bosons. It has been predicted3,4 that a quasi-equilibrium system of bosons could undergo Bose–Einstein Condensation even at relatively high temperatures, if the flow rate of energy pumped into the system exceeds a critical value. Here we report the observation of Bose–Einstein Condensation in a gas of magnons at room temperature. Magnons are the quanta of magnetic excitations in a magnetically ordered ensemble of magnetic moments. In thermal equilibrium, they can be described by Bose–Einstein statistics with zero chemical potential and a temperature-dependent density. In the experiments presented here, we show that by using a technique of microwave pumping it is possible to excite additional magnons and to create a gas of quasi-equilibrium magnons with a non-zero chemical potential. With increasing pumping intensity, the chemical potential reaches the energy of the lowest magnon state, and a Bose condensate of magnons is formed.
D Zvezdov - One of the best experts on this subject based on the ideXlab platform.
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bose Einstein Condensation of magnons in atomic hydrogen gas
Physical Review Letters, 2015Co-Authors: O Vainio, J Ahokas, J Jarvinen, L Lehtonen, Steffen Novotny, S Sheludiakov, Kalleantti Suominen, S Vasiliev, D ZvezdovAbstract:: We report on experimental observation of Bose-Einstein Condensation (BEC)-like behavior of quantized electron spin waves (magnons) in a dense gas of spin-polarized atomic hydrogen. The magnons are trapped and controlled with inhomogeneous magnetic fields and described by a Schrodinger-like wave equation, in analogy to the BEC experiments with neutral atoms. We have observed the appearance of a sharp feature in the ESR spectrum displaced from the normal spin wave spectrum. We believe that this observation corresponds to a sudden growth of the ground-state population of the magnons and emergence of their spontaneous coherence for hydrogen gas densities exceeding a critical value, dependent on the trapping potential. We interpret the results as a BEC of nonequilibrium magnons which were formed by applying the rf power.
Sajeev John - One of the best experts on this subject based on the ideXlab platform.
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photonic crystal architecture for room temperature equilibrium bose Einstein Condensation of exciton polaritons
Physical Review X, 2014Co-Authors: Jianhua Jiang, Sajeev JohnAbstract:Bose-Einstein condensates have previously been shown to exist at cryogenic temperatures. New results reveal that a microcavity based on CdTe can yield room-temperature, equilibrium Bose-Einstein Condensation.
G V Shlyapnikov - One of the best experts on this subject based on the ideXlab platform.
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bose Einstein Condensation in trapped dipolar gases
Physical Review Letters, 2000Co-Authors: L Santos, G V Shlyapnikov, P Zoller, Maciej LewensteinAbstract:We discuss Bose-Einstein Condensation in a trapped gas of bosonic particles interacting dominantly via dipole-dipole forces. We find that in this case the mean-field interparticle interaction and, hence, the stability diagram are governed by the trapping geometry. Possible physical realizations include ultracold heteronuclear molecules, or atoms with laser induced electric dipole moments.
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bose Einstein Condensation in quasi 2d trapped gases
Physical Review Letters, 2000Co-Authors: G V Shlyapnikov, D S Petrov, Markus HolzmannAbstract:We discuss Bose-Einstein Condensation (BEC) in quasi-2D trapped gases and find that well below the transition temperature ${T}_{c}$ the equilibrium state is a true condensate, whereas at intermediate temperatures $Tl{T}_{c}$ one has a quasicondensate (condensate with fluctuating phase). The mean-field interaction in a quasi-2D gas is sensitive to the frequency ${\ensuremath{\omega}}_{0}$ of the (tight) confinement in the ``frozen'' direction, and one can switch the sign of the interaction by changing ${\ensuremath{\omega}}_{0}$. Variation of ${\ensuremath{\omega}}_{0}$ can also reduce the rates of inelastic processes. This offers promising prospects for tunable BEC in trapped quasi-2D gases.