Is it possible to add indexes in Greek letters in geom_text?

Question

I'm plotting a graphic, and I need to put an index on my greek letter, like $\lambda_1$ and $\lambda_2$. But I just don't know hot to put these indexes $1$ and $2$ into $\lambda$'s.

Here is what I tried:

 gridd1 = c(0.10, 1.08, 8.92, 9.90) 
 gridd2 = c(0.10, 1.08, 8.92, 9.90) 
 gridd = expand.grid(gridd1,gridd2)
 grid1 = gridd$Var1
 grid2 = gridd$Var2
 gridd<-    
  data.frame(x=gridd$Var1,y=gridd$Var2,col=as.character("Other Points"),stringsAsFactors=FALSE)
 gridd[c(1,2,5,6),"col"]<-"A"
 gridd[c(3,4,7,8),"col"]<-"B"
 gridd[c(9,10,13,14),"col"]<-"c"
 gridd[c(11,12,15,16),"col"]<-"D"

bellow is the code for the graphic

ggplot(gridd, aes(x=grid1, y=grid2, group=col)) +
  geom_point(aes(shape=col, color=col, size = col),show.legend = FALSE)+
  scale_shape_manual(values=c(19,19,19,19))+
  coord_cartesian(xlim = c(.42, 9.57), ylim = c(.43,9.6))+
  scale_size_manual(values=c(4,4,4,4)) +
  scale_color_manual(values=c('green','blue','yellow','black'))+
  #geom_abline(slope=1, intercept=0)+
  geom_hline(yintercept=4.8)+
  geom_text(label ="lambda",
            parse = TRUE, x = 5, y = 7.5,cex=10)+
  geom_text(label ="lambda",
            parse = TRUE, x = 5, y = 2.5,cex=10)

I expect to put indexes 1 and 2, for the $\lambda$'s on the graphic. I tried to using lambda_1, without success.