Emergence of Artificial Photons in an Optical Lattice

Tewari, Sumanta; Scarola, V. W.; Senthil, T.; Sarma, S. Das

doi:10.1103/physrevlett.97.200401

Cited by 35 publications

(50 citation statements)

References 23 publications

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“…This is in contrast to the common approach to derive effective many-body terms from Hubbard models involving two-body interactions, which are obtained in a J U perturbation theory, and are thus necessarily small. 24 The main part of the present work is concerned with the microscopic derivation of the Hamiltonian in Eq. (2), and the tunability of the parameters by external fields.…”

Section: Fig 1: Strengths Of the Dominant Three-body Interactionsmentioning

confidence: 99%

Three-body interactions with cold polar molecules

Büchler¹,

Micheli²,

Zoller³

2007

Nature Phys

280

319

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We show that polar molecules driven by microwave fields give naturally rise to strong three-body interactions, while the two-particle interaction can be independently controlled and even switched off. The derivation of these effective interaction potentials is based on a microscopic understanding of the underlying molecular physics, and follows from a well controlled and systematic expansion into many-body interaction terms. For molecules trapped in an optical lattice, we show that these interaction potentials give rise to Hubbard models with strong nearest-neighbor two-body and three-body interaction. As an illustration, we study the one-dimensional Bose-Hubbard model with dominant three-body interaction and derive its phase diagram.Fundamental interactions between particles, such as the Coulomb law, involves pairs of particles, and our understanding of the plethora of phenomena in condensed matter physics rests on models involving effective twobody interactions. On the other hand, exotic quantum phases, such as topological phases or spin liquids, are often identified as ground states of Hamiltonians with three or more body terms. While the study of these phases and properties of their excitations is presently one of the most exciting developments in theoretical condensed matter physics, it is difficult to identify real physical systems exhibiting such properties -a noticeable exception being the Fractional Quantum Hall effect. Here we show that polar molecules in optical lattices driven by microwave fields give naturally rise to Hubbard models with strong nearest-neighbor three-body interactions, while the twobody terms can be tuned (even switched off) with external fields.The many-body Hamiltonians underlying condensed matter physics are derived within an effective low energy theory, obtained by integrating out the high energy excitations. In general, this gives rise to interaction termswhere V (r) describes the two-particle interaction depending only on the separation between the particles. The second term W (r i , r j , r k ) is the three-body interaction, which depends on the distance and orientation of three particles, and vanishes if one particle is far apart from the other two. The ellipsis denotes possible higher many-body term terms. While for Helium atoms in the context of superfluidity the two-particle interaction dominates and determines the ground state properties with the three-body interactions providing small corrections, 1 model Hamiltonians with strong three-body interactions have attracted a lot of interest in the search for microscopic Hamiltonians exhibiting exotic ground state properties. Well known examples are the fractional quantum Hall states described by the Pfaffian wave functions which appear as ground states of a Hamiltonian with three-body interaction. 2,3,4 These topological phases admit anyonic excitations with non-abelian braiding statistic. Of special interest are also spin systems and bosonic Hamiltonians with complex many-body interactions, such as ring exchange model, whic...

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Section: Fig 1: Strengths Of the Dominant Three-body Interactionsmentioning

confidence: 99%

Three-body interactions with cold polar molecules

Büchler¹,

Micheli²,

Zoller³

2007

Nature Phys

280

319

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“…The expansion of observables in terms of occupancies [Eq. (12)] is a general procedure that can be applied to other order parameters. We also define a core superfluid stiffness in terms of doubly occupied sites.…”

Section: Core Compressibility and Core Stiffnessmentioning

confidence: 99%

“…Ongoing work seeks to explore properties of interesting but poorly understood quantum many-body states using quantum degenerate atoms. Proposals include the use of optical lattice bosons to study novel superfluid order in higher bands [7][8][9] or topological phases [10][11][12]. Fermi gases in optical lattices are also under study as a route to explore the controversial phase diagram of the Fermi-Hubbard model [6,13,14].…”

Section: Introductionmentioning

confidence: 99%

Boson core compressibility

Khorramzadeh¹,

Lin²,

Scarola³

2012

Phys. Rev. A

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Strongly interacting atoms trapped in optical lattices can be used to explore phase diagrams of Hubbard models. Spatial inhomogeneity due to trapping typically obscures distinguishing observables. We propose that measures using boson double occupancy avoid trapping effects to reveal two key correlation functions. We define a boson core compressibility and core superfluid stiffness in terms of double occupancy. We use quantum Monte Carlo on the Bose-Hubbard model to empirically show that these quantities intrinsically eliminate edge effects to reveal correlations near the trap center. The boson core compressibility offers a generally applicable tool that can be used to experimentally map out phase transitions between compressible and incompressible states.

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“…Thus, experiments with polar molecules go beyond quantum simulation of effective theories motivated by electronic systems and aim at exploring a genuinely new domain of many-body quantum behavior, unique to dipolar interactions. Dipolar interactions can be utilized to generate long-range interactions of arbitrary shape using microwave fields [11], simulate exotic spin Hamiltonians [12,13] and are theoretically predicted to give rise to numerous interesting collective phenomena such as roton softening [14][15][16], supersolidity [17][18][19][20][21], p-wave superfluidity [22], emergence of artificial photons [23], bilayer quantum phase transitions [24], multi-layer self-assembled chains [25] for bosonic molecules, dimerization and inter-layer pairing [26,27], spontaneous inter-layer coherence [28], itinerant ferroelectricity [29], anisotropic Fermi liquid theory and anisotropic sound modes [30][31][32][33], fractional quantum Hall effect [34], Wigner crystallization [35], density-wave and striped order [36,37], biaxial nematic phase [38], topological superfluidity [39] and Z 2 topological phase [40], just to mention a few.…”

Section: Introductionmentioning

confidence: 99%

Collective phenomena in a quasi-two-dimensional system of fermionic polar molecules: Band renormalization and excitons

Babadi

Demler

2011

Phys. Rev. A

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We theoretically analyze a quasi-two-dimensional system of fermionic polar molecules in a harmonic transverse confining potential. The renormalized energy bands are calculated by solving the Hartree-Fock equation numerically for various trap and dipolar interaction strengths. The inter-subband excitations of the system are studied in the conserving time-dependent Hartree-Fock (TDHF) approximation from the perspective of lattice modulation spectroscopy experiments. We find that the excitation spectrum consists of both intersubband particle-hole excitation continuums and anti-bound excitons, arising from the anisotropic nature of dipolar interactions. The excitonic modes capture the majority of the spectral weight. We also evaluate the inter-subband transition rates in order to investigate the nature of the excitonic modes and find that they are antibound states formed from particle-hole excitations arising from several subbands. Our results indicate that the excitonic effects are present for interaction strengths and temperatures accessible in current experiments with polar molecules. I. INTRODUCTIONIn the past decade, much of the experimental and theoretical progress in the field of ultracold atoms [1][2][3] are motivated by the prospect of realizing novel strongly correlated many-body states of matter. In particular, experimental realization of quantum degenerate gases of fermionic polar molecules has witnessed a very rapid progress. By association of atoms via a Feshbach resonance to form deeply bound ultracold molecules [4,5], a nearly degenerate gas of KRb polar molecules in their rotational and vibrational ground state has been recently realized [6][7][8][9][10]. The molecules can be polarized by applying a d.c. electric field, resulting in strong dipole-dipole inter-molecular interactions.A strikingly new feature of systems of fermionic polar molecules is the anisotropy of dipolar interactions, making them unparalleled among the traditional condensed matter systems. Thus, experiments with polar molecules go beyond quantum simulation of effective theories motivated by electronic systems and aim at exploring a genuinely new domain of many-body quantum behavior, unique to dipolar interactions. Dipolar interactions can be utilized to generate long-range interactions of arbitrary shape using microwave fields [11], simulate exotic spin Hamiltonians [12,13] and are theoretically predicted to give rise to numerous interesting collective phenomena such as roton softening [14][15][16] Despite the theoretical prediction of numerous exotic quantum many-body phenomena in polar molecules, realization and observation of many of these novel predictions are still an experimental challenge. At the time this paper was written, the coldest gas of fermionic polar molecules has been realized with KRb molecules at a temperature of 1.4 T F [6-10], where T F is the Fermi temperature. The majority of the mentioned quantum phenomena require strong suppression of thermal fluctuations, i.e. strong degeneracy condition (T T F ).A major...

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Emergence of Artificial Photons in an Optical Lattice

Cited by 35 publications

References 23 publications

Three-body interactions with cold polar molecules

Three-body interactions with cold polar molecules

Boson core compressibility

Collective phenomena in a quasi-two-dimensional system of fermionic polar molecules: Band renormalization and excitons

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