Unconventional Superconductivity in Magic-Angle Twisted Trilayer Graphene

TL;DR

This paper investigates the unconventional superconductivity in magic-angle twisted trilayer graphene, highlighting the role of spin-fluctuations, phase diagram features, and the effects of electric fields, with implications for experimental detection.

Contribution

It introduces a theoretical framework linking spin-fluctuations to nematic superconductivity and maps the phase diagram, including the influence of electric fields on superconducting regions.

Findings

Superconducting dome with $T_c \\approx 2$ K between fillings -2 and -3.

Nematic superconductivity is influenced by spin-fluctuations and electric fields.

Signatures in local density of states are detectable by scanning tunneling spectroscopy.

Abstract

Magic-angle twisted trilayer graphene (MATTG) recently emerged as a highly tunable platform for studying correlated phases of matter, such as correlated insulators and superconductivity. Superconductivity occurs in a range of doping levels that is bounded by van Hove singularities which stimulates the debate of the origin and nature of superconductivity in this material. In this work, we discuss the role of spin-fluctuations arising from atomic-scale correlations in MATTG for the superconducting state. We show that in a phase diagram as function of doping ($\nu$) and temperature, nematic superconducting regions are surrounded by ferromagnetic states and that a superconducting dome with $T_c \approx 2\,\mathrm{K}$ appears between the integer fillings $\nu =-2$ and $\nu = -3$. Applying a perpendicular electric field enhances superconductivity on the electron-doped side which we relate to changes in the spin-fluctuation spectrum. We show that the nematic unconventional superconductivity leads to pronounced signatures in the local density of states detectable by scanning tunneling spectroscopy measurements.