Quantum twist angle disorder hides 2D superconductor signature

Ilaria Maccari of ETH Zurich, Louk Rademaker of the University of Geneva and Leiden University, and Giulia Venditti of the University of Geneva demonstrate that spatially correlated disorder in two-dimensional superconductors can obscure a hallmark transition known as the BKT transition, replacing it with a “smeared percolative transition”. Their work reveals that twist angle inhomogeneities, naturally occurring in moiré systems like twisted multilayer graphene, can effectively hide the ability to distinguish between different types of superconducting order at low temperatures. The researchers propose using the real part of conductivity as a diagnostic tool to assess the impact of this correlated disorder. Elasticity theory reveals that twist angle inhomogeneities, inherent to moiré structures, exhibit logarithmic long-range correlations, a finding that fundamentally alters expectations for two-dimensional superconductivity. These correlations arise from the solid’s response to atomic-scale defects, creating a spatially fluctuating landscape of local superconducting properties. The research demonstrates…