Polarons in two-dimensional atomic crystals

The polaron is the archetypal example of a quasiparticle emerging from the interaction between fermionic and bosonic fields in quantum field theory. In crystalline solids, polarons are formed when electrons and holes become dressed by the quanta of lattice vibrations. While experimental signatures of polarons in bulk three-dimensional materials abound, only rarely have polarons been observed in two-dimensional atomic crystals. Here, we shed light on this asymmetry by developing a quantitative ab initio theory of polarons in atomically-thin crystals. Using this conceptual framework, we unravel the real-space structure of the recently-observed hole polaron in hexagonal boron nitride, we discover an unexpected critical condition for the existence of polarons in two-dimensional crystals, and we establish the key materials descriptors and the universal laws that underpin polaron physics in two dimensions.