  The creation of pseudo-magnetic fields in strained graphene has emerged as a
promising route to allow observing intriguing physical phenomena that would be
unattainable with laboratory superconducting magnets. Scanning tunneling
spectroscopy experiments have successfully measured the pseudo-Landau levels
and proved the existence of pseudo-magnetic fields in various strained graphene
systems. These giant pseudo-magnetic fields observed in highly deformed
graphene can substantially alter the optical properties of graphene beyond a
level that can be feasible with an external magnetic field, but the
experimental signatures of the influence of such pseudo-magnetic fields have
yet to be unveiled. Here, using time-resolved infrared pump-probe spectroscopy,
we provide unambiguous evidence for ultra-slow carrier dynamics enabled by
pseudo-magnetic fields in periodically strained graphene. Strong
pseudo-magnetic fields of ~100 T created by non-uniform strain in graphene
nanopillars are found to significantly decelerate the relaxation processes of
hot carriers by more than an order of magnitude. Our finding presents
unforeseen opportunities for harnessing the new physics of graphene enabled by
pseudo-magnetic fields for optoelectronics and condensed matter physics.
