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Author: Hsiang-Hsuan Hung
Publisher:
ISBN: 9781124841243
Category :
Languages : en
Pages : 179
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Book Description
The progress of ultracold atoms renders numerous possibilities to investigate exotic magnetism and superfluidity, which are rarely observed in solid state systems. In this thesis, we will introduce two novel physical descriptions: "frustrated Cooper pairing" and "large-hyperfine spin physics". Geometric frustration in quantum magnetism refers to which magnetic interactions on different bonds cannot be simultaneously minimized, and usually Cooper pairing favors uniform phases among different lattice sites. Here, we introduce "frustration" in Cooper pairing in a fermionic p-orbital model. By mean-field calculations, we show that the system exhibits behavior analogous to frustrated magnetism, and an unconventional supersolid state with the f-wave symmetry. Next, we introduce large-spin physics. In usual condensed matter systems, large spin is not intriguing because large values of spin suppress quantum fluctuations. In contrast, in ultracold fermion systems, large-hyperfine spin enhances quantum fluctuations and brings exotic quantum magnetism. Here the simplest large-spin fermionic system, a spin-3/2 exchange system is proposed, which can be characterized by an Sp(4)/SO(5) symmetry. In one dimension, the ground states exhibit either a dimerized state with a finite spin gap or a gapless spin liquid state by means of the density matrix renormalization group method. In the latter case, the spin-spin correlation functions are identified to have 4-site periodicities, which behaves similarly to the SU(4) chain. In two dimension, we infer that there exist three competing phases: Neel ordering, columnar dimerization and 2 x 2 plaquette formation, in the thermodynamic limit by exact diagonalization calculation on small sizes. Finally we perform the projector Quantum Monte Carlo method to study another large-spin system: the half-filled SU(N) Hubbard model. We show that at half-filling there is no sign problem such that our simulations are accurate. By finite size scaling, it is clearly found that the magnetic Neel ordering can exist not only for N = 2 but also in the N = 4 case at strong interactions. For N>̲ 6 or N = 4 at small U, the numerical results do not have any prominent signal that the long-range ordering exists in the thermodynamic limit. Due to strong finite size effects and finite numerical accuracy, however, we are unable to make any conclusion to identify the physics in the regimes.
Author: Hsiang-Hsuan Hung
Publisher:
ISBN: 9781124841243
Category :
Languages : en
Pages : 179
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Book Description
The progress of ultracold atoms renders numerous possibilities to investigate exotic magnetism and superfluidity, which are rarely observed in solid state systems. In this thesis, we will introduce two novel physical descriptions: "frustrated Cooper pairing" and "large-hyperfine spin physics". Geometric frustration in quantum magnetism refers to which magnetic interactions on different bonds cannot be simultaneously minimized, and usually Cooper pairing favors uniform phases among different lattice sites. Here, we introduce "frustration" in Cooper pairing in a fermionic p-orbital model. By mean-field calculations, we show that the system exhibits behavior analogous to frustrated magnetism, and an unconventional supersolid state with the f-wave symmetry. Next, we introduce large-spin physics. In usual condensed matter systems, large spin is not intriguing because large values of spin suppress quantum fluctuations. In contrast, in ultracold fermion systems, large-hyperfine spin enhances quantum fluctuations and brings exotic quantum magnetism. Here the simplest large-spin fermionic system, a spin-3/2 exchange system is proposed, which can be characterized by an Sp(4)/SO(5) symmetry. In one dimension, the ground states exhibit either a dimerized state with a finite spin gap or a gapless spin liquid state by means of the density matrix renormalization group method. In the latter case, the spin-spin correlation functions are identified to have 4-site periodicities, which behaves similarly to the SU(4) chain. In two dimension, we infer that there exist three competing phases: Neel ordering, columnar dimerization and 2 x 2 plaquette formation, in the thermodynamic limit by exact diagonalization calculation on small sizes. Finally we perform the projector Quantum Monte Carlo method to study another large-spin system: the half-filled SU(N) Hubbard model. We show that at half-filling there is no sign problem such that our simulations are accurate. By finite size scaling, it is clearly found that the magnetic Neel ordering can exist not only for N = 2 but also in the N = 4 case at strong interactions. For N>̲ 6 or N = 4 at small U, the numerical results do not have any prominent signal that the long-range ordering exists in the thermodynamic limit. Due to strong finite size effects and finite numerical accuracy, however, we are unable to make any conclusion to identify the physics in the regimes.
Author: Fernanda Pinheiro
Publisher: Springer
ISBN: 3319434640
Category : Science
Languages : en
Pages : 137
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Book Description
This highly interdisciplinary thesis covers a wide range of topics relating to the interface of cold atoms, quantum simulation, quantum magnetism and disorder. With a self-contained presentation, it provides a broad overview of the rapidly evolving area of cold atoms and is of interest to both undergraduates and researchers working in the field. Starting with a general introduction to the physics of cold atoms and optical lattices, it extends the theory to that of systems with different multispecies atoms. It advances the theory of many-body quantum systems in excited bands (of optical lattices) through an extensive study of the properties of both the mean-field and strongly correlated regimes. Particular emphasis is given to the context of quantum simulation, where as shown here, the orbital degree of freedom in excited bands allows the study of exotic models of magnetism not easily achievable with the previous alternative systems. In addition, it proposes a new model Hamiltonian that serves as a quantum simulator of various disordered systems in different symmetry classes that can easily be reproduced experimentally. This is of great interest, especially for the study of disorder in 2D quantum systems.
Author: Maciej Lewenstein
Publisher: OUP Oxford
ISBN: 0191627437
Category : Science
Languages : en
Pages : 494
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Book Description
Quantum computers, though not yet available on the market, will revolutionize the future of information processing. Quantum computers for special purposes like quantum simulators are already within reach. The physics of ultracold atoms, ions and molecules offer unprecedented possibilities of control of quantum many body systems and novel possibilities of applications to quantum information processing and quantum metrology. Particularly fascinating is the possibility of using ultracold atoms in lattices to simulate condensed matter or even high energy physics. This book provides a complete and comprehensive overview of ultracold lattice gases as quantum simulators. It opens up an interdisciplinary field involving atomic, molecular and optical physics, quantum optics, quantum information, condensed matter and high energy physics. The book includes some introductory chapters on basic concepts and methods, and then focuses on the physics of spinor, dipolar, disordered, and frustrated lattice gases. It reviews in detail the physics of artificial lattice gauge fields with ultracold gases. The last part of the book covers simulators of quantum computers. After a brief course in quantum information theory, the implementations of quantum computation with ultracold gases are discussed, as well as our current understanding of condensed matter from a quantum information perspective.
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Advances in pure optical trapping techniques now allow the creation of degenerate Bose gases with internal degrees of freedom. Systems such as 87Rb, 39K or 23Na in the F = 1 hyperfine state offer an ideal platform for studying the interplay of super fluidity and quantum magnetism. Motivated by the experimental developments, we study ground state phases of a two-component Bose gas loaded on an optical lattice. We describe this effectively by the Bose-Hubbard Hamiltonian with onsite and near neighbor spin-spin interactions. One important feature of our investigation is the inclusion of interconversion (spin-flip) terms between the two species, which has been observed in optical lattice experiments. Furthermore, using mean-field theory and quantum Monte Carlo simulations, we map out the phase diagram of the system. A rich variety of phases is identified, including antiferromagnetic (AF) Mott insulators, ferromagnetic and AF super fluids.
Author: G. E. Volovik
Publisher: World Scientific
ISBN: 9789810207069
Category : Science
Languages : en
Pages : 244
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Book Description
This book discusses the unique properties of superfluid phases of 3He, the condensed matter with the outmost broken symmetry, which combine in a surprising way the properties of ordered magnets, liquid crystals and superfluids. The complicated vacuum state of these phases with a large number of fermionic and bosonic quasiparticles and topological objects remains the vacuum in modern quantum field theories. Some of the objects and physical phenomena in 3He have strong analogy with the neutrino, W-bosons, weak interactions, gravity, chiral anomaly, Quantum Hall Effect and fractional statistics. As an example of topological objects, the quantized vortices in 3He phases are discussed in detail, including singular and continuous vortices, half-quantum vortices, broken symmetry in the vortex core and phase transitions between the vortex states with different symmetry and topology.
Author: Wujie Huang
Publisher:
ISBN:
Category :
Languages : en
Pages : 176
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Book Description
Quantum simulation is emerging as an exciting and active frontier in atomic physics. It allows us not only to verify existing models with high precision, but also to engineer novel systems with strong correlations and exotic topologies. Recent efforts have been made to include synthetic gauge fields and spin-orbit couplings into ultracold quantum gas experiments, which would enable us to study the quantum Hall effect, topological insulators as well as topological superfluids. This thesis will describe the experimental implementation of a new spin-orbit coupled system using pseudospin-1/2 in an optical superlattices, as well as progress towards detecting the stripe phase in this system. The first part of this thesis describes the development of a new apparatus for performing quantum simulations with sodium and lithium in optical lattices. A quantum simulation program is challenging itself, therefore having a stable platform for preparing quantum gases is essential for this task. We'll describe our development in reliable and efficient production of sodium Bose-Einstein condensates and lithium degenerate Fermi gases, as well as the characterization of our optical lattice system in a superfluid to a Mott-insulator quantum phase transition. The dynamics of a Bloch oscillation in a tilted lattice has also been studied as an important step towards the implementation of synthetic magnetic fields in our system. The second part of this thesis describes the experimental realization of spin-orbit coupling in a pseudospin-1/2 system using an optical superlattice. This new scheme uses orbital states in a tilted double-well as the pseudospins, therefore does not require near-resonant Raman light to flip the spins and promise longer lifetimes compared to earlier spin-orbit coupling experiments in atomic gases. It also features a robust miscible ground state with stationary density stripes, which is closely related to the concept of supersolidity in condensed matter systems. We'll present our experimental implementation of this new system, signatures of the resonant spin-orbit coupling, as well as progress toward experimental detection of the stripe phase via Bragg scattering. This pseudospin-1/2 system could also be used for simulating quantum magnetism,and potentially novel models with topological properties and Majorana excitations.
Author: Maciej Lewenstein
Publisher: Oxford University Press
ISBN: 0199573123
Category : Science
Languages : en
Pages : 494
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Book Description
This book explores the physics of atoms frozen to ultralow temperatures and trapped in periodic light structures. It introduces the reader to the spectacular progress achieved on the field of ultracold gases and describes present and future challenges in condensed matter physics, high energy physics, and quantum computation.
Author: Karl-Heinz Bennemann
Publisher: OUP Oxford
ISBN: 0191029998
Category : Science
Languages : en
Pages : 657
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Book Description
Volume 2 of Novel Superfluids continues the presentation of recent results on superfluids, including novel metallic systems, superfluid liquids, and atomic/molecular gases of bosons and fermions, particularly when trapped in optical lattices. Since the discovery of superconductivity (Leyden, 1911), superfluid 4He (Moscow and Cambridge, 1937), superfluid 3He (Cornell, 1972), and observation of Bose-Einstein Condensation (BEC) of a gas (Colorado and MIT, 1995), the phenomenon of superfluidity has remained one of the most important topics in physics. Again and again, novel superfluids yield surprising and interesting behaviors. The many classes of metallic superconductors, including the high temperature perovskite-based oxides, MgB2, organic systems, and Fe-based pnictides, continue to offer challenges. The technical applications grow steadily. What the temperature and field limits are remains illusive. Atomic nuclei, neutron stars and the Universe itself all involve various aspects of superfluidity, and the lessons learned have had a broad impact on physics as a whole.
Author: M. Inguscio
Publisher: IOS Press
ISBN: 1614996946
Category : Science
Languages : en
Pages : 590
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Book Description
The Enrico Fermi summer school on Quantum Matter at Ultralow Temperatures held on 7-15 July 2014 at Varenna, Italy, featured important frontiers in the field of ultracold atoms. For the last 25 years, this field has undergone dramatic developments, which were chronicled by several Varenna summer schools, in 1991 on Laser Manipulation of Atoms, in 1998 on Bose-Einstein Condensation in Atomic Gases, and in 2006 on Ultra-cold Fermi Gases. The theme of the 2014 school demonstrates that the field has now branched out into many different directions, where the tools and precision of atomic physics are used to realise new quantum systems, or in other words, to quantum-engineer interesting Hamiltonians. The topics of the school identify major new directions: Quantum gases with long range interactions, either due to strong magnetic dipole forces, due to Rydberg excitations, or, for polar molecules, due to electric dipole interactions; quantum gases in lower dimensions; quantum gases with disorder; atoms in optical lattices, now with single-site optical resolution; systems with non-trivial topological properties, e.g. with spin-orbit coupling or in artificial gauge fields; quantum impurity problems (Bose and Fermi polarons); quantum magnetism. Fermi gases with strong interactions, spinor Bose-Einstein condensates and coupled multi-component Bose gases or Bose-Fermi mixtures continue to be active areas. The current status of several of these areas is systematically summarized in this volume.
Author: Mario G Rasetti
Publisher: World Scientific
ISBN: 9814513962
Category : Science
Languages : en
Pages : 242
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Book Description
This collection of articles provides authoritative and up-to-date reviews on the Hubbard Model. It will be useful to graduate students and researchers in the field.
