Ultracold atom

Physics

Crossover

Embedded system

Thermalisation

Artificial intelligence

Composite material

Ecology

Materials science

Integrable system

Range (aeronautics)

Bose gas

Trapping

Thermal equilibrium

Ideal gas

Bose–Einstein condensate

Mathematical physics

Computer science

Atom (system on chip)

Quantum mechanics

Quantum

Biology

Physical Review Letters

The emergence of a special type of fluidlike behavior at large scales in one-dimensional (1D) quantum integrable systems, theoretically predicted in O. A. Castro-Alvaredo et al., Emergent Hydrodynamics in Integrable Quantum Systems Out of Equilibrium, Phys. Rev. X 6, 041065 (2016) and B. Bertini et al., Transport in Out-of-Equilibrium XXZ Chains: Exact Profiles of Charges and Currents, Phys. Rev. Lett. 117, 207201 (2016), is established experimentally, by monitoring the time evolution of the in situ density profile of a single 1D cloud of Rb87 atoms trapped on an atom chip after a quench of the longitudinal trapping potential. The theory can be viewed as a dynamical extension of the thermodynamics of Yang and Yang, and applies to the whole range of repulsive interaction strength and temperature of the gas. The measurements, performed on weakly interacting atomic clouds that lie at the crossover between the quasicondensate and the ideal Bose gas regimes, are in very good agreement with the theory. This contrasts with the previously existing "conventional" hydrodynamic approach—that relies on the assumption of local thermal equilibrium—which is unable to reproduce the experimental data.Received 24 October 2018Revised 12 December 2018DOI:https://doi.org/10.1103/PhysRevLett.122.090601© 2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBose gasesCold atoms & matter wavesCold gases in optical latticesNonequilibrium statistical mechanicsQuantum quenchQuantum statistical mechanicsAtomic, Molecular & OpticalCondensed Matter, Materials & Applied PhysicsStatistical Physics

Generalized Hydrodynamics on an Atom Chip