Quantum Monte Carlo study of magnetic ordering and superconducting pairing symmetry in twisted bilayer graphene

Shi-Chao Fang, Guang-Kun Liu, Hai-Qing Lin, and Zhong-Bing Huang
Phys. Rev. B 100, 115135 – Published 16 September 2019

Abstract

To understand correlated insulating and unconventional superconducting states in twisted bilayer graphene, we perform a systematic study of spin and pairing correlations in an effective two-orbital Hubbard model, by using the ground-state constrained-path quantum Monte Carlo method. Our numerical simulations reveal that when only the on-site Hubbard U is considered, the long-range magnetic order develops for U3.2t at half filling. Upon doping away from half filling, an analysis based on the pairing correlations and corresponding vertex contributions identifies that pairing with the d+id symmetry is the dominant pairing channel. As the on-site Coulomb interaction is increased, both spin correlation and effective pairing interaction are enhanced simultaneously, indicating the intimate relation between magnetism and superconductivity. An inclusion of nearest neighbor Coulomb interaction V results in a suppression of the d+id superconductivity, but it can survive in the small V regime. Our findings are useful for clarifying the ongoing controversy on the superconducting pairing symmetry in twisted bilayer graphene.

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  • Received 23 May 2019
  • Revised 10 September 2019

DOI:https://doi.org/10.1103/PhysRevB.100.115135

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Shi-Chao Fang1, Guang-Kun Liu2, Hai-Qing Lin2, and Zhong-Bing Huang1,2,*

  • 1Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062, China
  • 2Beijing Computational Science Research Center, Beijing 100193, China

  • *huangzb@hubu.edu.cn

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Issue

Vol. 100, Iss. 11 — 15 September 2019

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