I have this piece of code
\begin{equation}
\begin{split}
n_1 &= Tr (O^{eff} \sigma_1 ) \\
&= Tr\Bigg [O^{eff} \begin{pmatrix} 0 & 1 \\ 1 & 0 \end{pmatrix} \Bigg ] \\
\end{split}
\end{equation}
and I get this when I compile with texmaker
Copy-pasted the same code in Overleaf, the 2x2 matrix looks normal. Any ideas?
Here is a list of the packages I use:
\usepackage{siunitx}
\usepackage{dcolumn}
\usepackage{sidecap}
\usepackage{braket}
\usepackage{amsmath}
\usepackage{caption}
\usepackage{wrapfig}
\usepackage{bbold}
\usepackage{amsthm}
\usepackage{url}
\usepackage{titlesec}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{appendix}

