Electroweak Z-string in Two-Higgs-Doublet Standard Model
  We derive electroweak Z-string solutions in the Glashow-Weinberg-Salam model with two Higgs doublets. The existence of such solutions in particular requires a specific relation between the ratio of the two Higgs vacuum expectation values, {\it i.e.} $\tan\beta$, and the couplings in the Higgs potential. 
HoSeong La