Magnetic Phases of Large-Spin Ultracold Bosons: Quantum Dimer Models and Spin Liquid Phases
by
 
Rutkowski, Todd C., author.

Title
Magnetic Phases of Large-Spin Ultracold Bosons: Quantum Dimer Models and Spin Liquid Phases

Author
Rutkowski, Todd C., author.

ISBN
9780355941784

Personal Author
Rutkowski, Todd C., author.

Physical Description
1 electronic resource (184 pages)

General Note
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
 
Advisors: Michael Lawler Committee members: Pegor Aynajian; Christof Grewer; Charles Nelson.

Abstract
This thesis investigates the plausibility of producing a quantum spin liquid (QSL) with ultracold bosonic atoms optically confined to the Mott insulating state. QSLs have received a great deal of attention for being an antiferromagnetic groundstate with many exotic properties, including the absence of local order, long-range entanglement, and fractionalized excitations. However, the identification and characterization of these phases in solid state systems remains a great challenge. Here we outline an alternate route to uncovering the QSL phase, which from the nature of spin angular momentum for ultracold atoms encounters many properties unique to these systems along the way. This proposal is possible because the magnetic exchange interactions for Mott insulating ultracold atoms are mediated by the hopping of whole atoms. Whole-atom exchange---a unique property of cold atoms---allows large fluctuations between the quantized Zeeman sublevels of each atomic spin. As we demonstrate, these fluctuations increase when large-spin atoms are used, or when interactions are tuned via optical Feshbach resonance (OFR). These strong quantum spin fluctuations inhibit classical magnetic ordering, and lead to a QSL ground state.
 
To illustrate the relationship between the spin magnitude, interaction strength, and QSL ground state, we present two distinct approaches to solving the relevant Hamiltonian. With mean field theory we find that for large spin (f > 2), and strong scattering through the spin-singlet channel, that magnetically-ordered Bose-Einstein condensates are unstable to the formation of a QSL. We then utilize Rayleigh-Schodinger perturbation theory to derive an effective Hamiltonian for our system in the Hilbert space of nearest-neighbor singlet coverings. At large spin this Hamiltonian produces a type of quantum dimer model (QDM), which are known to possess QSL phases. We derive the QDM parameters t, t' and V as a function of spin on several lattices, finding they scale with the inverse number of Zeeman sublevels. We then determine the proximity of the physically accessible states to the QSL phase, and discuss how other regions of the phase diagram may be accessed. We then conclude by highlighting several advantages to studying QSLs and QDMs with ultracold bosons.

Local Note
School code: 0792

Subject Term
Physics.
 
Condensed matter physics.
 
Atomic physics.

Added Corporate Author
State University of New York at Binghamton. Physics, Applied Physics, and Astronomy.

Electronic Access
http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:10816619


Shelf NumberItem BarcodeShelf LocationShelf LocationHolding Information
XX(681396.1)681396-1001Proquest E-Thesis CollectionProquest E-Thesis Collection