R package ‘latex2exp’

library(latex2exp)
alpha=seq(1,20)
beta=runif(20)
plot(alpha,beta)

Add in maths symbols: TeX()

par(mar=c(6,6,1,1))
plot(alpha,beta,xlab=TeX('$\\alpha$'),ylab=TeX('$\\beta$'),cex.lab=1.2)

Add in sub and superscripts

par(mar=c(6,6,1,1))
plot(alpha,beta^3,xlab=TeX('$\\alpha_{22}$'),ylab=TeX('$\\beta^3$'),
     cex.lab=1.2)

Add in normal text

par(mar=c(6,6,1,1))
plot(alpha,beta^3,xlab=TeX('Some parameter, $\\alpha_{22}$'),ylab=TeX('Some other parameter,  $\\beta^3$ (m$^2$)'))