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Magnetic phases of orbital bipartite optical lattices
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.
Number of Authors: 22020 (English)In: New Journal of Physics, E-ISSN 1367-2630, Vol. 22, no 2, article id 023023Article in journal (Refereed) Published
Abstract [en]

In the Hamburg cold atom experiment with orbital states in an optical lattice, s- and p-orbital atomic states hybridize between neighboring sites. In this work we show how this alternation of sites hosting s- and p-orbital states gives rise to a plethora of different magnetic phases, quantum and classical. We focus on phases whose properties derive from frustration originating from a competition between nearest and next nearest neighboring exchange interactions. The physics of the Mott insulating phase with unit filling is described by an effective spin-1/2 Hamiltonian showing great similarities with the J(1)-J(2) model. Based on the knowledge of the J(1)-J(2) model, supported by numerical simulations, we discuss the possibility of a quantum spin liquid phase in the present optical lattice system. In the superfluid regime we consider the parameter regime where the s-orbital states can be adiabatically eliminated to give an effective model for the p-orbital atoms. At the mean-field level we derive a generalized classical XY model, and show that it may support maximum frustration. When quantum fluctuations can be disregarded, the ground state should be a spin glass.

Place, publisher, year, edition, pages
2020. Vol. 22, no 2, article id 023023
Keywords [en]
cold atoms, optical lattice, phase diagram, quantum simulation, magnetic models
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-182921DOI: 10.1088/1367-2630/ab6cdfISI: 000537571400001OAI: oai:DiVA.org:su-182921DiVA, id: diva2:1447308
Available from: 2020-06-25 Created: 2020-06-25 Last updated: 2024-01-17Bibliographically approved
In thesis
1. A quantum for a quantum: Quantum simulators in exotic lattices
Open this publication in new window or tab >>A quantum for a quantum: Quantum simulators in exotic lattices
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis centers on how to use exotic lattices in different ways to design potential quantum simulators. These exotic lattices are either real physical objects in the form of ultra cold atoms in  bipartite optical lattice systems or lattice models revealed in state space. For optical lattices, the potential wells forms a lattice, such that the atoms of the system will be highly localized at the potential minima, and where the bipartite nature of the lattice ensures that the lattice sites will alternate between two different types.  When studying the atoms in the optical lattices they can be described by a Bose-Hubbard model, where it turns out that bipartite lattice systems provides a route to realizing frustration through competing nearest and next nearest neighbor couplings in both the superfluid phase and the Mott insulating phase.

For state space lattices are no longer objects in real space, but instead they live in state space. Though such state space lattice models can be represented as single particle systems, they still hold a potential for realizing quantum simulators. For this type of exotic lattices, the focus is on how to study quantum optical models in terms of their Fock space lattices (FSLs). Such models only have a few degrees-of-freedom which together with symmetries of these system, make it simple to identify the emerging FSLs with know lattice models from the condensed matter. Thus shedding new light on the quantum optical systems at hand. The three-mode Jaynes-Cummings model in the large detuned limit, is used as an example to display the strength of this method. It is the growth of a systems state space, that determines whether the system is a potential quantum simulator or not. For a system to be a quantum simulator, the growth of the phase space has to be such, that it becomes computational hard to find the systems energy. This means, that if we can design a state space lattice, which grows exponential, then we have a potential candidate for a quantum simulator. The Bethe lattice is one such example that grows exponentially.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2022. p. 148
Keywords
quantum physics, condensed matter physics, quantum optics, optical lattices. Fock state lattices, exotic lattices, frustration
National Category
Condensed Matter Physics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-206468 (URN)978-91-7911-940-9 (ISBN)978-91-7911-941-6 (ISBN)
Public defence
2022-09-09, Albano, details about the location is available at the department website, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2022-08-17 Created: 2022-06-15 Last updated: 2022-08-10Bibliographically approved

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Saugmann, PilLarson, Jonas

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