Sans serif symbols in XeLaTeX

Question

I want to introduce a family of sans serif symbols using the TeX Gyre Heros italic font. I have only managed to use the upright font, How do I achieve this with the italic font?

\documentclass{article}
\usepackage{fontspec}
\setmathsf{TeX Gyre Heros}

\newcommand{\sfmu}{\mathsf{μ}}

\begin{document}

\[
\sfmu : X \to Y
\]

\end{document}

Answer 1

You can search "texgyrehero" in your computer and you can get a font texgyreheros-italic.otf, set mathsf to it like

\documentclass{article}
\usepackage{fontspec}
\setmathsf{texgyreheros-italic.otf}

\newcommand{\sfmu}{\mathsf{μ}}

\begin{document}

\[
\sfmu : X \to Y
\]

\end{document}

Another solution: Use unicode-math package

First you can refer to Greek sans serif math .

And you can try another opentype font which support "Math" script, like "Fira Math". Here are two examples:

1. If you want to use sans serif \mu in total paper, you can use

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{latinmodern-math.otf}
\setmathfont[range=\mitmu]{FiraMath-Regular.otf}

\begin{document}

\[
    \mitmu : X \to Y,
\]

\end{document}

2. As you said, you can declare a sfit family, here I call it fira, you can use

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{latinmodern-math.otf}
\setmathfontface\fira{FiraMath-Regular.otf}


\begin{document}

\[
    \fira{\mupmu, \mitmu} : X \to Y,
\]

\end{document}

3. If you insist on using TeX Gyre Heros, you can use

\documentclass{article}
\usepackage{amsmath}
\usepackage{unicode-math}
\setmathfont{latinmodern-math.otf}
\setmathfontface\sfit{texgyreheros-italic.otf}
\setmathfontface\sfup{texgyreheros-regular.otf}

\begin{document}

\[
    \sfit{\mupmu}, \sfup{\mupmu} : X \to Y,
\]

\end{document}

Because TeX Gyre Heros doesn't contain "Math" script, so we can't use \sfit{\mitmu} to get a italic \mu.

In those examples, \mupmu is a command declared by unicode-math, which means m(math)up(upright)mu(μ), so you can easily guess what \mitmu means.