  We study the persistent current in a one dimensional Dirac ring and show that
the change of spin current with respect to an applied perpendicular electric
field can be used to identify the topological phases. We further study the
effect of Rashba spin orbit coupling and show that the Aharonov-Casher phase
appearing due to Rashba spin orbit coupling vanishes in topologically
nontrivial regime and thus can identify the topological phases. This
Aharonov-Casher phase causes a finite spin-valley current in presence of valley
mixing perturbation and is thus useful to detect the topological phases even in
presence of such impurity.
