We calculate the band structure of ultracold atoms located inside a laser-driven optical cavity. For parameters where the atom-cavity system exhibits bistability, the atomic band structure develops loop structures akin to the ones predicted for Bose-Einstein condensates in ordinary (noncavity) optical lattices. However, in our case the nonlinearity derives from the cavity back-action rather than from direct interatomic interactions. We find both bi- and tristable regimes associated with the lowest band, and show that the multistability we observe can be analyzed in terms of swallowtail catastrophes. Dynamic and energetic stability of the mean-field solutions is also discussed, and we show that the bistable solutions have, as expected, one unstable and two stable branches. The presence of loops in the atomic band structure has important implications for proposals concerning Bloch oscillations of atoms inside optical cavities [Peden et al., Phys. Rev. A 80, 043803 (2009); Prasanna Venkatesh et al., Phys. Rev. A 80, 063834 (2009)].We calculate the band structure of ultracold atoms located inside a laser-driven optical cavity. For parameters where the atom-cavity system exhibits bistability, the atomic band structure develops loop structures akin to the ones predicted for Bose-Einstein condensates in ordinary (noncavity) optical lattices. However, in our case the nonlinearity derives from the cavity back-action rather than from direct interatomic interactions. We find both bi- and tristable regimes associated with the lowest band, and show that the multistability we observe can be analyzed in terms of swallowtail catastrophes. Dynamic and energetic stability of the mean-field solutions is also discussed, and we show that the bistable solutions have, as expected, one unstable and two stable branches. The presence of loops in the atomic band structure has important implications for proposals concerning Bloch oscillations of atoms inside optical cavities [Peden et al., Phys. Rev. A 80, 043803 (2009); Prasanna Venkatesh et al., Phys. Rev. A 80, 063834 (2009)].

arXiv:1101.1570Physical Review AJun 7, 201126 citations

Nonlinear atomic cavity for ultracold atoms

Weiping Zhang, Pierre Meystre, Ewan M. Wright

Aug 24, 20050 citations

Controlling higher-orbital quantum phases of ultracold atoms via coupling to optical cavities

Hui Tan, Jinsen Han, Wei Zheng +2 more

The orbital degree of freedom plays an important role in understanding exotic phenomena of strongly correlated materials. In this work, we study strongly correlated ultracold bosonic gases coupled to a high-finesse cavity, pumped by a blue-detuned laser in the transverse direction. By controlling the reflection of the pump laser, we find that atoms can be selectively transferred to the odd-parity $p$ -orbital band or to the even-parity $d$ -orbital band of a two-dimensional square lattice, accompanied by pronounced cavity-photon excitations. By interacting with the cavity field, atoms self-organize to form stable higher-orbital superfluid and Mott-insulating phases with orbital-density waves, as a result of cavity-induced orbital-flip hoppings. Our study opens a route to manipulate orbital degrees of freedom in strongly correlated quantum gases via coupling to optical cavities.The orbital degree of freedom plays an important role in understanding exotic phenomena of strongly correlated materials. In this work, we study strongly correlated ultracold bosonic gases coupled to a high-finesse cavity, pumped by a blue-detuned laser in the transverse direction. By controlling the reflection of the pump laser, we find that atoms can be selectively transferred to the odd-parity $p$-orbital band or to the even-parity $d$-orbital band of a two-dimensional square lattice, accompanied by pronounced cavity-photon excitations. By interacting with the cavity field, atoms self-organize to form stable higher-orbital superfluid and Mott-insulating phases with orbital-density waves, as a result of cavity-induced orbital-flip hoppings. Our study opens a route to manipulate orbital degrees of freedom in strongly correlated quantum gases via coupling to optical cavities.

arXiv:2108.10495Physical Review AAug 24, 20225 citations

Experiments with Ultracold Atoms in an Optical Cavity

Subhadeep Gupta, Kevin L. Moore, Thomas Purdy +3 more

Bulletin of the American Physical SocietyMar 22, 20050 citations

Quantum Control with Ultracold Atoms

Ivan Deutsch

Bulletin of the American Physical SocietyMar 10, 20080 citations

Probing Bloch band geometry with ultracold atoms in optical lattices

Tracy M.W.Y. Li

Ultracold atoms in optical lattices have recently emerged as promising candidates for investigating the geometric and topological aspects of band structures. In this thesis, we exploit the high degree of control available in these systems to directly probe the band geometry of an optical honeycomb lattice. In the first series of experiments, we realize an atomic interferometer in quasimomentum space to measure the singular Berry flux associated with a Dirac point. This technique enables us to determine the distribution of Berry curvature in the Brillouin zone with high quasimomentum resolution. Next, we realize strong-force dynamics that are described by matrix-valued Wilson lines, which are generalizations of the Berry phase to degenerate systems. In this strong-force regime, we show that the evolution in the band populations directly reveals the band geometry. This method enables the reconstruction of both the cell-periodic Bloch states at every quasimomentum and the eigenvalues of Wilson-Zak loops. Our techniques can be used to determine the topological invariants, such as the Chern and Z2 numbers, that characterize the band structure. Lastly, having established our ability to detect the band geometry, we present preliminary experiments on engineering band structures.Ultracold atoms in optical lattices have recently emerged as promising candidates for investigating the geometric and topological aspects of band structures. In this thesis, we exploit the high degree of control available in these systems to directly probe the band geometry of an optical honeycomb lattice. In the first series of experiments, we realize an atomic interferometer in quasimomentum space to measure the singular Berry flux associated with a Dirac point. This technique enables us to determine the distribution of Berry curvature in the Brillouin zone with high quasimomentum resolution. Next, we realize strong-force dynamics that are described by matrix-valued Wilson lines, which are generalizations of the Berry phase to degenerate systems. In this strong-force regime, we show that the evolution in the band populations directly reveals the band geometry. This method enables the reconstruction of both the cell-periodic Bloch states at every quasimomentum and the eigenvalues of Wilson-Zak loops. Our techniques can be used to determine the topological invariants, such as the Chern and Z2 numbers, that characterize the band structure. Lastly, having established our ability to detect the band geometry, we present preliminary experiments on engineering band structures.

Jan 1, 20160 citations

p

-orbital band or to the even-parity

d

-orbital band of a two-dimensional square lattice, accompanied by pronounced cavity-photon excitations. By interacting with the cavity field, atoms self-organize to form stable higher-orbital superfluid and Mott-insulating phases with orbital-density waves, as a result of cavity-induced orbital-flip hoppings. Our study opens a route to manipulate orbital degrees of freedom in strongly correlated quantum gases via coupling to optical cavities.