Change geom_text to bold when parse=TRUE

Question

I am annotating faceted plots to include a superscript, yet am having trouble making the text bold. I realise that this has something to do with creating an expression outside the plot call and then specifying parse=TRUE. There is probably quite a simple solution but so far nothing I have tried has worked, including the use of bquote() and bold(). Thanks

library(ggplot2)

data(iris)

rsq<-c(.3,.6,.75)
pos<-c(5,6,7)
Species<-levels(iris$Species)

big_data<-as.data.frame(cbind(pos, rsq))
big_data$Species<-Species

lab <- paste("r^2 == ", round(big_data$rsq,2))

ggplot(iris, aes(x=Sepal.Length, y=Sepal.Width)) +
  facet_wrap(~Species,scales='free_x')+
  geom_point(size=3,show.legend = F) +
  geom_text(aes(x=pos,y=1,label=as.character(lab)),parse=TRUE,data=big_data,fontface='bold')

Answer 1

A little cheat - over plotting the text 3 times with slight increases in size.

ggplot(iris, aes(x=Sepal.Length, y=Sepal.Width)) +
  facet_wrap(~Species,scales='free_x')+
  geom_point(size=3,show.legend = F) +
  geom_text(aes(x=pos,y=1,label=as.character(lab)),parse=TRUE,data=big_data,size=4)+
  geom_text(aes(x=pos,y=1,label=as.character(lab)),parse=TRUE,data=big_data,size=4.07)+
  geom_text(aes(x=pos,y=1,label=as.character(lab)),parse=TRUE,data=big_data,size=4.08)