Superfluid density and collective modes of fermion superfluid in dice lattice

Abstract The superfluid properties of attractive Hubbard model in dice lattice are investigated. It is found that three superfluid order parameters increase as the interaction increases. When the filling factor falls into the flat band, due to the infinite large density of states, the resultant supe...

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Autores principales:	Yu-Rong Wu, Xiao-Fei Zhang, Chao-Fei Liu, Wu-Ming Liu, Yi-Cai Zhang
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/f53df59bd4b0470c91e08fb3838e6325
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spelling	oai:doaj.org-article:f53df59bd4b0470c91e08fb3838e63252021-12-02T18:18:51ZSuperfluid density and collective modes of fermion superfluid in dice lattice10.1038/s41598-021-93007-z2045-2322https://doaj.org/article/f53df59bd4b0470c91e08fb3838e63252021-06-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-93007-zhttps://doaj.org/toc/2045-2322Abstract The superfluid properties of attractive Hubbard model in dice lattice are investigated. It is found that three superfluid order parameters increase as the interaction increases. When the filling factor falls into the flat band, due to the infinite large density of states, the resultant superfluid order parameters are proportional to interaction strength, which is in striking contrast with the exponentially small counterparts in usual superfluid (or superconductor). When the interaction is weak, and the filling factor is near the bottom of the lowest band (or the top of highest band), the superfluid density is determined by the effective mass of the lowest (or highest) single-particle band. When the interaction is strong and filling factor is small, the superfluid density is inversely proportional to interaction strength, which is related to effective mass of tightly bound pairs. In the strong interaction limit and finite filling, the asymptotic behaviors of superfluid density can be captured by a parabolic function of filling factor. Furthermore, when the filling is in flat band, the superfluid density shows a logarithmic singularity as the interaction approaches zero. In addition, there exist three undamped collective modes for strong interactions. The lowest excitation is gapless phonon, which is characterized by the total density oscillations. The two others are gapped Leggett modes, which correspond relative density fluctuations between sublattices. The collective modes are also reflected in the two-particle spectral functions by sharp peaks. Furthermore, it is found that the two-particle spectral functions satisfy an exact sum-rule, which is directly related to the filling factor (or density of particle). The sum-rule of the spectral functions may be useful to distinguish between the hole-doped and particle-doped superfluid (superconductor) in experiments.Yu-Rong WuXiao-Fei ZhangChao-Fei LiuWu-Ming LiuYi-Cai ZhangNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-17 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Yu-Rong Wu Xiao-Fei Zhang Chao-Fei Liu Wu-Ming Liu Yi-Cai Zhang Superfluid density and collective modes of fermion superfluid in dice lattice
description	Abstract The superfluid properties of attractive Hubbard model in dice lattice are investigated. It is found that three superfluid order parameters increase as the interaction increases. When the filling factor falls into the flat band, due to the infinite large density of states, the resultant superfluid order parameters are proportional to interaction strength, which is in striking contrast with the exponentially small counterparts in usual superfluid (or superconductor). When the interaction is weak, and the filling factor is near the bottom of the lowest band (or the top of highest band), the superfluid density is determined by the effective mass of the lowest (or highest) single-particle band. When the interaction is strong and filling factor is small, the superfluid density is inversely proportional to interaction strength, which is related to effective mass of tightly bound pairs. In the strong interaction limit and finite filling, the asymptotic behaviors of superfluid density can be captured by a parabolic function of filling factor. Furthermore, when the filling is in flat band, the superfluid density shows a logarithmic singularity as the interaction approaches zero. In addition, there exist three undamped collective modes for strong interactions. The lowest excitation is gapless phonon, which is characterized by the total density oscillations. The two others are gapped Leggett modes, which correspond relative density fluctuations between sublattices. The collective modes are also reflected in the two-particle spectral functions by sharp peaks. Furthermore, it is found that the two-particle spectral functions satisfy an exact sum-rule, which is directly related to the filling factor (or density of particle). The sum-rule of the spectral functions may be useful to distinguish between the hole-doped and particle-doped superfluid (superconductor) in experiments.
format	article
author	Yu-Rong Wu Xiao-Fei Zhang Chao-Fei Liu Wu-Ming Liu Yi-Cai Zhang
author_facet	Yu-Rong Wu Xiao-Fei Zhang Chao-Fei Liu Wu-Ming Liu Yi-Cai Zhang
author_sort	Yu-Rong Wu
title	Superfluid density and collective modes of fermion superfluid in dice lattice
title_short	Superfluid density and collective modes of fermion superfluid in dice lattice
title_full	Superfluid density and collective modes of fermion superfluid in dice lattice
title_fullStr	Superfluid density and collective modes of fermion superfluid in dice lattice
title_full_unstemmed	Superfluid density and collective modes of fermion superfluid in dice lattice
title_sort	superfluid density and collective modes of fermion superfluid in dice lattice
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/f53df59bd4b0470c91e08fb3838e6325
work_keys_str_mv	AT yurongwu superfluiddensityandcollectivemodesoffermionsuperfluidindicelattice AT xiaofeizhang superfluiddensityandcollectivemodesoffermionsuperfluidindicelattice AT chaofeiliu superfluiddensityandcollectivemodesoffermionsuperfluidindicelattice AT wumingliu superfluiddensityandcollectivemodesoffermionsuperfluidindicelattice AT yicaizhang superfluiddensityandcollectivemodesoffermionsuperfluidindicelattice
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Superfluid density and collective modes of fermion superfluid in dice lattice

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