  Ultrathin bismuth exhibits rich physics including strong spin-orbit coupling,
ferroelectricity, nontrivial topology, and light-induced structural dynamics.
We use \textit{ab initio} calculations to show that light can induce structural
transitions to four transient phases in bismuth monolayers. These light-induced
phases exhibit nontrivial topological character, which we illustrate using the
recently introduced concept of spin bands and spin-resolved Wilson loops.
Specifically, we find that the topology changes via the closing of the electron
and spin band gaps during photo-induced structural phase transitions, leading
to distinct edge states. Our study provides strategies to tailor electronic and
spin topology via ultrafast control of photo-excited carriers and associated
structural dynamics.
