  The interface between different quantum phases of matter can give rise to
novel physics, such as exotic topological phases or non-unitary conformal field
theories. Here we investigate the interface between two spin chains in
different chiral phases. Surprisingly, the mean-field theory description of
this interacting composite system is given in terms of Dirac fermions in a
curved space-time geometry. In particular, the boundary between the two phases
represents a black hole horizon. We demonstrate that this representation is
faithful both analytically, by employing bosonisation to obtain a Luttinger
liquid model, and numerically, by employing Matrix Product State methods. A
striking prediction from the black hole equivalence emerges when a quench, at
one side of the interface between two opposite chiralities, causes the other
side to thermalise with the Hawking temperature for a wide range of parameters
and initial conditions.
