Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:physics/0208065 · Physical Review Letters

Evanescent-Wave Trapping and Evaporative Cooling of an Atomic Gas at the Crossover to Two Dimensions

M. Hammes, D. Rychtarik, B. Engeser, Hanns‐Christoph Nägerl, Rudolf Grimm

Published Apr 29, 2003• 60 citations
arXivHTMLPDF

Abstract

A dense gas of cesium atoms at the crossover to two dimensions is prepared in a highly anisotropic surface trap that is realized with two evanescent light waves. Temperatures as low as 100 nK are reached with 20,000 atoms at a phase-space density close to 0.1. The lowest quantum state in the tightly confined direction is populated by more than 60%. The system provides atoms at a mean distance from the surface as low as 1 microm, and offers intriguing prospects for future experiments on degenerate quantum gases in two dimensions.

DOI
10.1103/physrevlett.90.173001

Related papers

Crossover to 2D in a double-evanescent wave trap

D. Rychtarik, B. Engeser, M. Hammes +2 more

\nWe report the preparation of a dense gas of cesium atoms at the\ncrossover to two-dimensionality in a highly anisotropic surface\ntrap that is realized with two evanescent light waves.\nTemperatures as low as 100 nK are reached with 20.000 atoms at a\nphase-space density close to 0.1. The lowest quantum state in the\ntightly confined direction is populated by more than 60%. The\nsystem offers intriguing prospects for future experiments on\ndegenerate quantum gases in two dimensions.\n

Journal de Physique IV (Proceedings)•Oct 1, 2004•1 citation

Evanescent-wave trapping of Cs at the crossover to two-dimensionality

D. Rychtarik, B. Engeser, M. Hammes +2 more

Summary form only given. Our experiment aims at investigating a two-dimensional degenerate quantum gas of cesium atoms. For this purpose, we exploit a double evanescent-wave trap (DEW trap) consisting of a repulsive and an attractive evanescent wave and providing a highly anisotropic dipole potential. Efficient loading is accomplished by a multi-stage sequence. Cesium atoms are laser cooled in a MOT and then transferred into a gravito-optical dipole trap that serves as a surface reservoir. In the next stage, the phase-space density is enhanced by creating a dimple in the potential with a far-detuned, attractive laser beam that is focused to the center of the reservoir. Finally, we transfer the atoms into the DEW trap. The vertical dipole potential provides a well close to the surface, and depends on the power of the attractive evanescent wave. Ramping down the power of the attractive evanescent wave leads to efficient evaporation. A situation at the crossover to two-dimensionality is reached when the thermal energy of k/sub B/ /spl times/ 100 nK equals the level spacing h/spl nu/; thus the vertical ground state is populated by over 60 percent. Since the final phase-space density is as high as 0.1, the creation of a degenerate two-dimensional quantum gas of Cs comes into experimental reach. In present experiments we polarize the atoms into the F = 3, m/sub F/ = 3 state. As a consequence of the resonant interaction properties of cesium, the scattering length can be tuned in a wide range by applying a magnetic field. We use the tunability of interactions to optimize the evaporation efficiency on the way to a two-dimensional degenerate quantum gas of cesium.

European Quantum Electronics Conference (EQEC)•Jan 1, 2003•0 citations

Evaporative cooling of cesium in a surface trap

M. Hammes, D. Rychtarik, В. В. Дружиніна +1 more

Summary form only given. Optical dipole traps facilitate storage of atoms independent of their magnetic sub-state. Trapping at high densities is thus not limited by two-body collisions changing the spin state of the atom, which in the particular case of cesium have so far prevented the attainment of Bose-Einstein condensation in magnetic traps. For evaporative cooling of Cs we use the gravito-optical surface trap (GOST) which consists of a horizontal evanescent-wave (EW) atom mirror in combination with a blue-detuned hollow beam (HE) for transverse confinement. Starting conditions for evaporative cooling are prepared by optical cooling, based on inelastic reflections from the EW.

Conference on Lasers and Electro-Optics•Aug 29, 2005•0 citations

Two-Dimensional Bose-Einstein Condensate in an Optical Surface Trap

D. Rychtarik, B. Engeser, Hanns‐Christoph Nägerl +1 more

We report on the creation of a two-dimensional Bose-Einstein condensate of cesium atoms in a gravito-optical surface trap. The condensate is produced a few microm above a dielectric surface on an evanescent-wave atom mirror. After evaporative cooling by all-optical means, expansion measurements for the tightly confined vertical motion show energies well below the vibrational energy quantum. The presence of a condensate is observed in two independent ways by a magnetically induced collapse at negative scattering length and by measurements of the horizontal expansion.

arXiv:cond-mat/0309536•Physical Review Letters•Apr 27, 2004•194 citations

Optical and evaporative cooling of caesium atoms in the gravito-optical surface trap

M. Hammes, D. Rychtarik, В. В. Дружиніна +3 more

We report on cooling of an atomic caesium gas closely above an evanescent-wave atom mirror. At high densities, optical cooling based on inelastic reflections is found to be limited by a density-dependent excess temperature and trap loss due to ultracold collisions involving repulsive molecular states. Nevertheless, very good starting conditions for subsequent evaporative cooling are obtained. Our first evaporation experiments show a temperature reduction from 10 μK down to 300 nK along with a gain in phase-space density of almost two orders of magnitude.

arXiv:physics/0005035•Journal of Modern Optics•Nov 1, 2000•31 citations

Cold atoms near a surface

Tilman Pfau, H. Gauck, Dominik Schneble +3 more

Two-dimensional systems are of great interest in physics as the celebrated quantum-Hall effects show, which are based on a 2D electron gas. Neutral systems involve thin He films and spin polarized atomic hydrogen in a cryogenic environment, where the successful creation of a 2D quasi-condensate was recently reported. Over the last years, with laser cooling and trapping techniques at hand, several schemes for the preparation of laser cooled atomic 2D gases have been proposed. Low dimensional gases are discussed as keys to achieve high density samples of purely optically cooled atoms, since the reabsorption of scattered photons is greatly suppressed compared to the situation in 3D. On the other hand, by structuring 2D waveguide light fields laterally, very versatile "integrated atom optical" elements can be realized. We have prepared a quasi-2D gas of argon atoms confined in a planar matter waveguide less than 1 /spl mu/m away from a reflecting surface. We trap metastable Ar/sup +/ atoms in the ls/sub 5/(J=2) state in a magneto-optical trap. Upon release, they fall towards a gold coated prism surface where an evanescent light field is generated by resonant excitation of surface plasmons in the gold layer. This light field is blue detuned from the 1s/sub 5//spl hArr/2p/sub 9/(J=3) transition and hence creates a repulsive potential which slows down the falling atoms.

Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR)•Jan 20, 2003•0 citations
A dense gas of cesium atoms at the crossover to two dimensions is prepared in a highly anisotropic surface trap that is realized with two evanescent light waves. Temperatures as low as 100 nK are reached with 20,000 atoms at a phase-space density close to 0.1. The lowest quantum state in the tightly confined direction is populated by more than 60%. The system provides atoms at a mean distance from the surface as low as 1 microm, and offers intriguing prospects for future experiments on degenerate quantum gases in two dimensions.
Summary form only given. Our experiment aims at investigating a two-dimensional degenerate quantum gas of cesium atoms. For this purpose, we exploit a double evanescent-wave trap (DEW trap) consisting of a repulsive and an attractive evanescent wave and providing a highly anisotropic dipole potential. Efficient loading is accomplished by a multi-stage sequence. Cesium atoms are laser cooled in a MOT and then transferred into a gravito-optical dipole trap that serves as a surface reservoir. In the next stage, the phase-space density is enhanced by creating a dimple in the potential with a far-detuned, attractive laser beam that is focused to the center of the reservoir. Finally, we transfer the atoms into the DEW trap. The vertical dipole potential provides a well close to the surface, and depends on the power of the attractive evanescent wave. Ramping down the power of the attractive evanescent wave leads to efficient evaporation. A situation at the crossover to two-dimensionality is reached when the thermal energy of k/sub B/ /spl times/ 100 nK equals the level spacing h/spl nu/; thus the vertical ground state is populated by over 60 percent. Since the final phase-space density is as high as 0.1, the creation of a degenerate two-dimensional quantum gas of Cs comes into experimental reach. In present experiments we polarize the atoms into the F = 3, m/sub F/ = 3 state. As a consequence of the resonant interaction properties of cesium, the scattering length can be tuned in a wide range by applying a magnetic field. We use the tunability of interactions to optimize the evaporation efficiency on the way to a two-dimensional degenerate quantum gas of cesium.
Summary form only given. Optical dipole traps facilitate storage of atoms independent of their magnetic sub-state. Trapping at high densities is thus not limited by two-body collisions changing the spin state of the atom, which in the particular case of cesium have so far prevented the attainment of Bose-Einstein condensation in magnetic traps. For evaporative cooling of Cs we use the gravito-optical surface trap (GOST) which consists of a horizontal evanescent-wave (EW) atom mirror in combination with a blue-detuned hollow beam (HE) for transverse confinement. Starting conditions for evaporative cooling are prepared by optical cooling, based on inelastic reflections from the EW.
We report on the creation of a two-dimensional Bose-Einstein condensate of cesium atoms in a gravito-optical surface trap. The condensate is produced a few microm above a dielectric surface on an evanescent-wave atom mirror. After evaporative cooling by all-optical means, expansion measurements for the tightly confined vertical motion show energies well below the vibrational energy quantum. The presence of a condensate is observed in two independent ways by a magnetically induced collapse at negative scattering length and by measurements of the horizontal expansion.
We report on cooling of an atomic caesium gas closely above an evanescent-wave atom mirror. At high densities, optical cooling based on inelastic reflections is found to be limited by a density-dependent excess temperature and trap loss due to ultracold collisions involving repulsive molecular states. Nevertheless, very good starting conditions for subsequent evaporative cooling are obtained. Our first evaporation experiments show a temperature reduction from 10 μK down to 300 nK along with a gain in phase-space density of almost two orders of magnitude.
Two-dimensional systems are of great interest in physics as the celebrated quantum-Hall effects show, which are based on a 2D electron gas. Neutral systems involve thin He films and spin polarized atomic hydrogen in a cryogenic environment, where the successful creation of a 2D quasi-condensate was recently reported. Over the last years, with laser cooling and trapping techniques at hand, several schemes for the preparation of laser cooled atomic 2D gases have been proposed. Low dimensional gases are discussed as keys to achieve high density samples of purely optically cooled atoms, since the reabsorption of scattered photons is greatly suppressed compared to the situation in 3D. On the other hand, by structuring 2D waveguide light fields laterally, very versatile "integrated atom optical" elements can be realized. We have prepared a quasi-2D gas of argon atoms confined in a planar matter waveguide less than 1 /spl mu/m away from a reflecting surface. We trap metastable Ar/sup +/ atoms in the ls/sub 5/(J=2) state in a magneto-optical trap. Upon release, they fall towards a gold coated prism surface where an evanescent light field is generated by resonant excitation of surface plasmons in the gold layer. This light field is blue detuned from the 1s/sub 5//spl hArr/2p/sub 9/(J=3) transition and hence creates a repulsive potential which slows down the falling atoms.