TY - JOUR

T1 - Vortex lattices in binary Bose-Einstein condensates

T2 - Collective modes, quantum fluctuations, and intercomponent entanglement

AU - Yoshino, Takumi

AU - Furukawa, Shunsuke

AU - Ueda, Masahito

N1 - Funding Information:
TY is grateful to Kazuya Fujimoto, Yuki Kawaguchi, and Terumichi Ohashi for stimulating discussions during his stay at Nagoya University. This work was supported by KAKENHI Grant Nos. JP18H01145 and JP18K03446, a Grant-in-Aid for Scientific Research on Innovative Areas ‘Topological Materials Science’ (KAKENHI Grant No. JP15H05855) from the Japan Society for the Promotion of Science (JSPS), and Keio Gijuku Academic Development Funds. TY was supported by JSPS through the Program for Leading Graduate School (ALPS).
Publisher Copyright:
© 2022 The Author(s). Published by IOP Publishing Ltd.

PY - 2022/5/18

Y1 - 2022/5/18

N2 - We study binary Bose-Einstein condensates subject to synthetic magnetic fields in mutually parallel or antiparallel directions. Within the mean-field theory, the two types of fields have been shown to give the same vortex-lattice phase diagram. We develop an improved effective field theory to study properties of collective modes and ground-state intercomponent entanglement. Here, we point out the need to introduce renormalized coupling constants for coarse-grained densities. We show that the low-energy excitation spectra for the two types of fields are related to each other by suitable rescaling with the renormalized coupling constants. By calculating the entanglement entropy, we find that for an intercomponent repulsion (attraction), the two components are more strongly entangled in the case of parallel (antiparallel) fields, in qualitative agreement with recent studies for a quantum (spin) Hall regime. We also find that the entanglement spectrum exhibits an anomalous square-root dispersion relation, which leads to a subleading logarithmic term in the entanglement entropy. All of these are confirmed by numerical calculations based on the Bogoliubov theory with the lowest-Landau-level approximation. Finally, we investigate the effects of quantum fluctuations on the phase diagrams by calculating the correction to the ground-state energy due to zero-point fluctuations in the Bogoliubov theory. We find that the boundaries between rhombic-, square-, and rectangular-lattice phases shift appreciably with a decrease in the filling factor.

AB - We study binary Bose-Einstein condensates subject to synthetic magnetic fields in mutually parallel or antiparallel directions. Within the mean-field theory, the two types of fields have been shown to give the same vortex-lattice phase diagram. We develop an improved effective field theory to study properties of collective modes and ground-state intercomponent entanglement. Here, we point out the need to introduce renormalized coupling constants for coarse-grained densities. We show that the low-energy excitation spectra for the two types of fields are related to each other by suitable rescaling with the renormalized coupling constants. By calculating the entanglement entropy, we find that for an intercomponent repulsion (attraction), the two components are more strongly entangled in the case of parallel (antiparallel) fields, in qualitative agreement with recent studies for a quantum (spin) Hall regime. We also find that the entanglement spectrum exhibits an anomalous square-root dispersion relation, which leads to a subleading logarithmic term in the entanglement entropy. All of these are confirmed by numerical calculations based on the Bogoliubov theory with the lowest-Landau-level approximation. Finally, we investigate the effects of quantum fluctuations on the phase diagrams by calculating the correction to the ground-state energy due to zero-point fluctuations in the Bogoliubov theory. We find that the boundaries between rhombic-, square-, and rectangular-lattice phases shift appreciably with a decrease in the filling factor.

KW - multicomponent Bose-Einstein condensates

KW - quantum entanglement

KW - synthetic gauge fields

KW - vortex lattices

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U2 - 10.1088/1361-6455/ac68b6

DO - 10.1088/1361-6455/ac68b6

M3 - Article

AN - SCOPUS:85130796291

SN - 0953-4075

VL - 55

JO - Journal of Physics B: Atomic, Molecular and Optical Physics

JF - Journal of Physics B: Atomic, Molecular and Optical Physics

IS - 10

M1 - 105302

ER -