Vignale, Giovanni

Email Address
c2dvg@nus.edu.sg


Organizational Units
OrgUnit Logo
Organizational Unit
OrgUnit Logo
Organizational Unit

Filters

2019 - 201912020 - 20211
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Publication
    Antiferromagnetism and chiral d-wave superconductivity from an effective $t-J-D$ model for twisted bilayer graphene
    (2019-01-31) Gu, Xingyu; Chen, Chuan; Leaw, Jia Ning; Laksono, Evan; Pereira, Vitor M; Vignale, Giovanni; Adam, Shaffique; Dr Chen Chuan; CENTRE FOR ADVANCED 2D MATERIALS; YALE-NUS COLLEGE; PHYSICS
    Starting from the strong-coupling limit of an extended Hubbard model, we develop a spin-fermion theory to study the insulating phase and pairing symmetry of the superconducting phase in twisted bilayer graphene. Assuming that the insulating phase is an anti-ferromagnetic insulator, we show that fluctuations of the anti-ferromagnetic order in the conducting phase can mediate superconducting pairing. Using a self-consistent mean-field analysis, we find that the pairing wave function has a chiral d-wave symmetry. Consistent with this observation, we show explicitly the existence of chiral Majorana edge modes by diagonalizing our proposed Hamiltonian on a finite-sized system. These results establish twisted bilayer graphene as a promising platform to realize topological superconductivity.
  • No Thumbnail Available
    Publication
    Carrier transport theory for twisted bilayer graphene in the metallic regime
    (NATURE PORTFOLIO, 2021-09-30) Sharma, Girish; Yudhistira, Indra; Chakraborty, Nilotpal; Ho, Derek YH; Al Ezzi, MM; Fuhrer, Michael S; Vignale, Giovanni; Adam, Shaffique; Assoc Prof Shaffique Adam; CENTRE FOR ADVANCED 2D MATERIALS; MATERIALS SCIENCE AND ENGINEERING
    Understanding the normal-metal state transport in twisted bilayer graphene near magic angle is of fundamental importance as it provides insights into the mechanisms responsible for the observed strongly correlated insulating and superconducting phases. Here we provide a rigorous theory for phonon-dominated transport in twisted bilayer graphene describing its unusual signatures in the resistivity (including the variation with electron density, temperature, and twist angle) showing good quantitative agreement with recent experiments. We contrast this with the alternative Planckian dissipation mechanism that we show is incompatible with available experimental data. An accurate treatment of the electron-phonon scattering requires us to go well beyond the usual treatment, including both intraband and interband processes, considering the finite-temperature dynamical screening of the electron-phonon matrix element, and going beyond the linear Dirac dispersion. In addition to explaining the observations in currently available experimental data, we make concrete predictions that can be tested in ongoing experiments.