How to match alignment of subscripts if one of main characters is \overline-d?

Question

I can align dagger and non-dagger expressions using, for example, $\psi_i^\dagger \psi_i^{\vphantom\dagger}$. How do I do the same for overlines, for example: in $\overline{\psi}_i \psi_i$, the subscript on the second $\psi$ will not be at the same height as the first one.

Answer 1

You should probably not be typing \overline{\psi}_i anyway -- try \bar{\psi}_i instead. For sure, the subscript in \psi_i has the same vertical position as in \bar{\psi}_i.

If for some reason you simply must write \overline{\psi}_i, you should write \psi^{}_i, i.e., insert an empty superscript "atom", in order to get a conformable vertical position (though not a perfectly equal vertical position) of the subscript.

\documentclass{article}
\begin{document}
$\bar{\psi}_i$ $\psi_i$ \quad $\overline{\psi}_i$ $\psi^{}_i$
\end{document}