Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi–Hubbard model

doi:10.1088/1674-1056/adfbd9

中国物理B ›› 2025, Vol. 34 ›› Issue (11): 117102-117102.doi: 10.1088/1674-1056/adfbd9

Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi–Hubbard model

Huaisong Zhao(赵怀松)¹, Feng Yuan(袁峰)^1,†, Tianxing Ma(马天星)^2,‡, and Peng Zou(邹鹏)^1,§

1 Centre for Theoretical and Computational Physics, College of Physics, Qingdao University, Qingdao 266071, China;
2 School of Physics and Astronomy, Beijing Normal University, Beijing 100875, China

收稿日期:2025-08-08 修回日期:2025-08-08 接受日期:2025-08-15 发布日期:2025-10-30
基金资助:
This work was supported by the National Natural Science Foundation of China [Grant Nos. U23A2073 (P.Z.) and 11547034 (H.Z.)].

Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi–Hubbard model

Huaisong Zhao(赵怀松)¹, Feng Yuan(袁峰)^1,†, Tianxing Ma(马天星)^2,‡, and Peng Zou(邹鹏)^1,§

1 Centre for Theoretical and Computational Physics, College of Physics, Qingdao University, Qingdao 266071, China;
2 School of Physics and Astronomy, Beijing Normal University, Beijing 100875, China

Received:2025-08-08 Revised:2025-08-08 Accepted:2025-08-15 Published:2025-10-30
Contact: Feng Yuan, Tianxing Ma, Peng Zou E-mail:yuan@qdu.edu.cn;txma@bnu.edu.cn;phy.zoupeng@gmail.com
Supported by:
This work was supported by the National Natural Science Foundation of China [Grant Nos. U23A2073 (P.Z.) and 11547034 (H.Z.)].

摘要/Abstract

摘要： The measurement of the pairing gap is crucial for investigating the physical properties of superconductors or superfluids. We propose a strategy to measure the pairing gap through the dynamical excitations. With the random phase approximation (RPA), we study the dynamical excitations of a two-dimensional attractive Fermi–Hubbard model by calculating its dynamical structure factor. Two distinct collective modes emerge: a Goldstone phonon mode at transferred momentum q = [0,0] and a roton mode at q = [π,π]. The roton mode exhibits a sharp molecular peak in the low-energy regime. Notably, the area under the roton molecular peak scales with the square of the pairing gap, which holds even in three-dimensional and spin–orbit coupled (SOC) optical lattices. This finding suggests an experimental approach to measure the pairing gap in lattice systems by analyzing the dynamical structure factor at q = [π,π].

关键词: attractive Fermi–Hubbard model, superfluid, dynamical excitations, roton mode, pairing gap measurement

Abstract: The measurement of the pairing gap is crucial for investigating the physical properties of superconductors or superfluids. We propose a strategy to measure the pairing gap through the dynamical excitations. With the random phase approximation (RPA), we study the dynamical excitations of a two-dimensional attractive Fermi–Hubbard model by calculating its dynamical structure factor. Two distinct collective modes emerge: a Goldstone phonon mode at transferred momentum q = [0,0] and a roton mode at q = [π,π]. The roton mode exhibits a sharp molecular peak in the low-energy regime. Notably, the area under the roton molecular peak scales with the square of the pairing gap, which holds even in three-dimensional and spin–orbit coupled (SOC) optical lattices. This finding suggests an experimental approach to measure the pairing gap in lattice systems by analyzing the dynamical structure factor at q = [π,π].

Key words: attractive Fermi–Hubbard model, superfluid, dynamical excitations, roton mode, pairing gap measurement

中图分类号: (Lattice fermion models (Hubbard model, etc.))

71.10.Fd

03.75.Kk (Dynamic properties of condensates; collective and hydrodynamic excitations, superfluid flow) 67.85.-d (Ultracold gases, trapped gases)

Huaisong Zhao(赵怀松), Feng Yuan(袁峰), Tianxing Ma(马天星), and Peng Zou(邹鹏). Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi–Hubbard model[J]. 中国物理B, 2025, 34(11): 117102-117102.

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Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi–Hubbard model

Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi–Hubbard model

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