Giovanni Vignale

@article{ISI:001247474400001,
title = {High conductivity from cross-band electron pairing in flat-band systems},
author = {Maxim Trushin and Liangtao Peng and Gargee Sharma and Giovanni Vignale and Shaffique Adam},
doi = {10.1103/PhysRevB.109.245118},
times_cited = {0},
issn = {2469-9950},
year = {2024},
date = {2024-06-13},
journal = {PHYSICAL REVIEW B},
volume = {109},
number = {24},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {Electrons in condensed matter may transition into a variety of broken-symmetry phase states due to electronelectron interactions. Applying diverse mean-field approximations to the interaction term is arguably the simplest way to identify the phase states theoretically possible in a given setting. Here, we explore electron-electron attraction in a two-band system comprising symmetric conduction and valence bands touching each other at a single point. We assume a mean-field pairing between the electrons having opposite spins, momenta, and in contrast to the conventional superconducting pairing, residing in opposite bands, i.e., having opposite energies. We show that electrons transition into a correlated ground state if and only if the bands are flat enough, i.e., the transition is impossible in the case of conventional parabolic bands. Although this state is not superconducting in the usual sense and does not exhibit a gap in its excitation spectrum, it is nevertheless immune to elastic scattering caused by any kind of disorder and is therefore expected to exhibit high electric conductivity at low temperature, mimicking the behavior of a real superconductor. Having in mind the recent experimental realizations of flat-band electronic systems in twisted multilayers, we foresee an exciting opportunity for observing a class of highly conductive materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{ISI:001173887400003,
title = {Theoretical determination of the effect of a screening gate on plasmon-induced superconductivity in twisted bilayer graphene},
author = {Liangtao Peng and Indra Yudhistira and Giovanni Vignale and Shaffique Adam},
doi = {10.1103/PhysRevB.109.045404},
times_cited = {1},
issn = {2469-9950},
year = {2024},
date = {2024-01-05},
journal = {PHYSICAL REVIEW B},
volume = {109},
number = {4},
publisher = {AMER PHYSICAL SOC},
address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA},
abstract = {The microscopic pairing mechanism for superconductivity in magic-angle twisted bilayer graphene remains an open question. Recent experimental studies seem to rule out a purely electronic mechanism due to the insensitivity of the critical superconducting temperature to either a highly doped screening layer or the proximity to a metallic screening gate. In this theoretical work, we explore the role of external screening layers on the superconducting properties of twisted bilayer graphene within a purely electronic mechanism. Consistent with the experimental observations, we find that the critical temperature is unaffected by screening unless the screening layer is closer than 3 nm from the superconductor. Thus, the available transport data are not in contradiction with a plasmon-mediated mechanism. We also investigate other properties of this plasmon-mediated superconductivity, including signatures in the tunneling density of states as probed in spectroscopy experiments.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}