  Hawking radiation, a manifestation of quantum field theory in curved
spacetime, has stimulated extensive theoretical and experimental studies of
various black-hole (BH) analogs. However, an undisputed confirmation of Hawking
radiation remains elusive. One challenge is BH analog structures with
long-lived horizons are difficult to achieve. Here, we theoretically
demonstrate a new type of optical BH analog based on light cone evolution
associated with topological phase transition of Dirac cones. The transition
from a type-II to type-I Dirac/Weyl cone creates an analogous curved spacetime
that crosses a type-III Dirac/Weyl cone, which affords a stationary
configuration of long-lived event horizon. Photons tunneling through the
horizon emit a spectrum of Hawking radiation. As an example, we design a
laboratory version in an inhomogeneous two-dimensional graphyne-like
topological photonic lattice with a Hawking temperature of 0.14 mK.
Understanding Hawking-like radiation in this unique topological BH is not only
of fundamental interest in its own right but may also provide new hints to
gravitational physics.
