  We present the fabrication and electrical transport characterization of
underdoped YBa$_2$Cu$_3$O$_{7-{\delta}}$ nanowires. The nanowires have been
realized without any protective capping layer and they show transport
properties similar to those of the parent thin film, demonstrating that they
have not been damaged by the nanopatterning. The current-voltage
characteristics of the underdoped nanowires show large hysteretic voltage
switching at the critical current, in contrast to the flux-flow like
characteristics of optimally doped nanostructures, indicating the formation of
a self-stabilizing hot spot. These results open up new possibilities of using
the underdoped nanowires for single photon detection and for exploring the
underdoped side of the YBa$_2$Cu$_3$O$_{7-{\delta}}$ phase diagram at the
nanoscale.
