Throughout physics, stable composite objects are usually formed by way of attractive forces, which allow the constituents to lower their energy by binding together. Repulsive forces separate particles in free space. However, in a structured environment such as a periodic potential and in the absence of dissipation, stable composite objects can exist even for repulsive interactions. Here we report the observation of such an exotic bound state, which comprises a pair of ultracold rubidium atoms in an optical lattice. Consistent with our theoretical analysis, these repulsively bound pairs exhibit long lifetimes, even under conditions when they collide with one another. Signatures of the pairs are also recognized in the characteristic momentum distribution and through spectroscopic measurements. There is no analogue in traditional condensed matter systems of such repulsively bound pairs, owing to the presence of strong decay channels. Our results exemplify the strong correspondence between the optical lattice physics of ultracold bosonic atoms and the Bose–Hubbard model1,2—a link that is vital for future applications of these systems to the study of strongly correlated condensed matter and to quantum information.
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Jaksch, D. & Zoller, P. The cold atom Hubbard toolbox. Ann. Phys. 315, 52–79 (2005)
Bloch, I. Ultracold quantum gases in optical lattices. Nature Phys. 1, 23–30 (2005)
Fisher, M. P. A., Weichman, P. B., Grinstein, G. & Fisher, D. S. Boson localization and the superfluid insulator transition. Phys. Rev. B. 40, 546–570 (1989)
Greiner, M., Mandel, O., Esslinger, T., Hänsch, T. W. & Bloch, I. Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms. Nature 415, 39–44 (2002)
Paredes, B. et al. Tonks–Girardeau gas of ultracold atoms in an optical lattice. Nature 429, 277–281 (2004)
Stöferle, T., Moritz, H., Schori, C., Köhl, M. & Esslinger, T. Transition from a strongly interacting 1D superfluid to a Mott insulator. Phys. Rev. Lett. 92, 130403 (2004)
Kinoshita, T., Wenger, T. & Weiss, D. S. Observation of a one-dimensional Tonks-Girardeau gas. Science 305, 1125–1128 (2004)
Laburthe Tolra, B. et al. Observation of reduced three-body recombination in a correlated 1D degenerate Bose gas. Phys. Rev. Lett. 92, 190401 (2004)
Fallani, L., Lye, J. E., Guarrera, V., Fort, C. & Inguscio, M. Onset of a Bose-glass of ultra-cold atoms in a disordered crystal of light. Preprint at http://arxiv.org/abs/cond-mat/0603655 (2006).
Fedichev, P. O., Bijlsma, M. J. & Zoller, P. Extended molecules and geometric scattering resonances in optical lattices. Phys. Rev. Lett. 92, 080401 (2004)
Ryu, C. et al. Raman-induced oscillation between an atomic and a molecular quantum gas. Preprint at http://arxiv.org/abs/cond-mat/0508201 (2005).
Stöferle, T., Moritz, H., Günter, K., Köhl, M. & Esslinger, T. Molecules of fermionic atoms in an optical lattice. Phys. Rev. Lett. 96, 030401 (2006)
Thalhammer, G. et al. Long-lived Feshbach molecules in a 3D optical lattice. Phys. Rev. Lett. 96, 050402 (2006)
Donley, E. A., Claussen, N. R., Thompson, S. T. & Wieman, C. E. Atom–molecule coherence in a Bose–Einstein condensate. Nature 417, 529–533 (2002)
Regal, C. A., Ticknor, C., Bohn, J. L. & Jin, D. S. Creation of ultracold molecules from a Fermi gas of atoms. Nature 424, 47–50 (2003)
Herbig, J. et al. Preparation of a pure molecular quantum gas. Science 301, 1510–1513 (2003)
Xu, K. et al. Formation of quantum-degenerate sodium molecules. Phys. Rev. Lett. 91, 210402 (2003)
Cubizolles, J., Bourdel, T., Kokkelmans, S. J. J. M. F., Shlyapnikov, G. V. & Salomon, C. Production of long-lived ultracold Li2 molecules from a Fermi gas. Phys. Rev. Lett. 91, 240401 (2003)
Dürr, S., Volz, T., Marte, A. & Rempe, G. Observation of molecules produced from a Bose-Einstein condensate. Phys. Rev. Lett. 92, 020406 (2004)
Koehler, T., Goral, K. & Julienne, P. S. Production of cold molecules via magnetically tunable Feshbach resonances. Preprint at http://arxiv.org/abs/cond-mat/0601420 (2006).
Vidal, G. Efficient classical simulation of slightly entangled quantum computations. Phys. Rev. Lett. 91, 147902 (2003)
Daley, A. J., Kollath, C., Schollwöck, U. & Vidal, G. Time-dependent density-matrix renormalization-group using adaptive effective Hilbert spaces. J. Stat. Mech. Theor. Exp. P04005 (2004)
White, S. R. & Feiguin, A. E. Real-time evolution using the density matrix renormalization group. Phys. Rev. Lett. 93, 076401 (2004)
Greiner, M., Bloch, I., Mandel, O., Hänsch, T. W. & Esslinger, T. Exploring phase coherence in a 2D lattice of Bose-Einstein condensates. Phys. Rev. Lett. 87, 160405 (2001)
Hecker Denschlag, J. et al. A Bose-Einstein condensate in an optical lattice. J. Phys. B. 35, 3095–3110 (2002)
Volz, T., Dürr, S., Ernst, S., Marte, A. & Rempe, G. Characterization of elastic scattering near a Feshbach resonance in 87Rb. Phys. Rev. A 68, 010702 (2003)
Joannopoulos, J. D., Meade, R. D. & Winn, J. N. Photonic Crystals: Molding the Flow of Light (Princeton Univ. Press, Princeton, 1995)
Berman, P. (ed.) Cavity Quantum Electrodynamics (Academic, New York, 1994)
Hofstetter, W., Cirac, J. I., Zoller, P., Demler, E. & Lukin, M. D. High-temperature superfluidity of fermionic atoms in optical lattices. Phys. Rev. Lett. 89, 220407 (2002)
Lewenstein, M., Santos, L., Baranov, M. A. & Fehrmann, H. Atomic Bose-Fermi mixtures in an optical lattice. Phys. Rev. Lett. 92, 050401 (2004)
We thank H. Ritsch for discussions, and M. Theis and S. Schmid for help in setting up the experiment. We acknowledge support from the Austrian Science Fund (FWF) within the Spezialforschungsbereich 15, from the European Union within the OLAQUI and SCALA networks, from the TMR network ‘Cold Molecules’, and from the Tiroler Zukunftsstiftung. Author Contributions This work is a collaboration between teams of experimental (K.W., G.T., F.L., R.G. and J.H.D.) and theoretical (A.J.D., A.K., H.P.B. and P.Z.) physicists.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
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Winkler, K., Thalhammer, G., Lang, F. et al. Repulsively bound atom pairs in an optical lattice. Nature 441, 853–856 (2006). https://doi.org/10.1038/nature04918
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