Turning a corner on entanglement entropy

Roger Melko (Waterloo)

The entanglement entropy of a quantum critical system receives a logarithmic contribution when the entangling boundary contains a sharp corner. Calculations on free and interacting quantum theories indicate that the coefficient of this logarithm is a new universal number. In particular, numerical results on interacting models tuned to 2+1 dimensional Wilson-Fisher fixed points indicate that this coefficient contains information about the low-energy theory, scaling for example with the number of vector components of the field. Recently, these numerical results have been confirmed analytically, revealing a relationship between the corner coefficient and a central charge defined from the stress tensor two-point correlation function. The combination of analytical understanding and easy numerical accessibility promises to make the corner entanglement an important theoretical tool, providing a new window on universality for a variety of conventional and unconventional quantum critical points encountered in condensed-matter systems.