Anomalous Weak Localisation Phase in Ultra-Clean van der Waals Heterostructures

Over the past two decades, two-dimensional (2D) van der Waals (vdW) materials have been the subject of numerous theoretical and experimental quantum transport investigations. In this talk we present a non-perturbative analysis of quantum corrections to the DC conductivity in 2D Dirac materials with symmetry-breaking spin-orbit coupling (SOC). We find that the commonly reported weak localisation to weak anti-localisation (WL-to-WAL) transition that is driven by increasing the strength of SOC is reversed in ultra-clean graphene heterostructures (i.e. WAL-to-WL). This counter-intuitive result can be traced back to the strong non-perturbative coupling between the pseudospin and spin degrees of freedom induced by SOC, which gaps out the delocalised modes of the Cooperon for large SOC strengths. Our results suggest that the nature of localisation in spin-orbit coupled 2D vdW materials is richer than first thought, highlighting the importance of non-perturbative methods in quantum interference studies of ultra-clean vdW heterostructures.