Abstract : Magic angles are a topic of current interest in condensed matter physics and refer to a remarkable theoretical (Bistritzer–MacDonald, 2011) and experimental (Jarillo-Herrero et al, 2018) discovery: two sheets of graphene twisted by a certain (magic) angle display unusual electronic properties, such as superconductivity. In this talk, we shall discuss a simple periodic Hamiltonian describing the chiral limit of twisted bilayer graphene (Tarnopolsky-Kruchkov-Vishwanath, 2019), whose spectral properties are thought to determine which angles are magical. We show that the corresponding eigenfunctions decay exponentially in suitable geometrically determined regions as the angle of twisting decreases, which can be viewed as a form of semiclassical analytic hypoellipticity. This is joint work with Maciej Zworski.

Keywords : twisted bilayer graphene; exponential decay; Poisson bracket