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Dynamics and Quantum Fluctuations of Many-body States of Interacting Ultracold Gases

Li, Zehan (2021) Dynamics and Quantum Fluctuations of Many-body States of Interacting Ultracold Gases. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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We explored interaction cold atoms in new quantum regimes that have no prior analogue in condensed matter materials in three related main topics. First, motivated by recent advance in orbitally tuned Feshbach resonance experiments, we analyze the ground-state phase diagram and related low-energy excitation spectra of a high partial wave interacting Bose gas. Remarkably different from what was previously known in the p-wave case, the atomic superfluid is found to be momentum-independent in the present d-wave case. What is more, we study the quantum fluctuations in the condensates of a mixture of bosonic atoms and molecules with interspecies p-wave interaction. Our analysis shows that the quantum phase of coexisting atomic and molecular condensates is unstable at the mean-field level. The quantum Lee-Huang-Yang correction to the mean-field energy provides a remarkable mechanism to self-stabilize the phase. The correlated order spontaneously breaks a rich set of global U(1) gauge, atomic spin, spatial rotation and translation, and time-reversal symmetries.
Second, we study the dynamics of a non-integrable spin chain model composed of two ingredients - a nearest neighbor Ising coupling, and an infinite range XX interaction. Unlike other fast scrambling many-body systems, this model is not known to be dual to a black hole. We demonstrate that our model exhibits fast scrambling for a wide parameter regime, accompanied by a fast growth of the entanglement entropy, as well as a swift change in the magnetization.
Third, to extend the study of the highly chaotic many-body model, we analyze the ground state phases of the model with a nearest neighbor XXZ interaction and an infinite range XX interaction. By employing spin-wave theory, we find that there is a large parameter regime where the continuous U(1) symmetry of this model is spontaneously broken, which is not possible in the absence of the infinite range interaction by the Mermin-Wagner theorem. Furthermore, we demonstrate that in the U(1) symmetry broken phase, the half chain entanglement entropy violates the area law logarithmically. Our work demonstrates that the interplay of short and long range interactions can lead to novel quantum phases of matter.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Li, Zehanzel6@pitt.eduzel60000-0002-4203-3156
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairLiu, W. Vincentwvliu@pitt.eduwvliu
Committee MemberBatell, Brianbatell@pitt.edubatell
Committee MemberBoyanovsky, Danielboyan@pitt.eduboyan
Committee MemberRothstein,
Committee MemberSnoke, Davidsnoke@pitt.edusnoke
Date: 3 May 2021
Date Type: Publication
Defense Date: 29 January 2021
Approval Date: 3 May 2021
Submission Date: 3 March 2021
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 134
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: p-wave interaction, d-wave interaction, fast scrambling, quantum phase
Date Deposited: 03 May 2021 15:25
Last Modified: 03 May 2021 15:25


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