[Tex/LaTex] Amsmath error occurs

amsmath

I have error

! Missing } inserted.

}
l.9 { -1+2/[1+3\exp(-2|J|/k_BT)],&
$T

MWE

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{eqnarray}  \label{eq:Cd}
\tilde C(T)=
\begin{cases}
{ -1+2/[1+3\exp(-2|J|/k_BT)],& $T<T_e$;\cr\cr 0,& $T\ge T_e$.\cr}
\end{cases}
\end{eqnarray}

\end{document}

When i comment \usepackage{amsmath} there is no error. I can't understand how to fix it, without \usepackage{amsmath} commenting.

Best Answer

The problem is you are trying to use math inside math: $T<T_e$. Take off those $$:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{eqnarray}  \label{eq:Cd}
\tilde C(T)=
\begin{cases}
    -1+2/[1+3\exp (-2|J|/k_BT)], & T<T_e \\ 0,& T\ge T_e.    \end{cases}
\end{eqnarray}

\end{document}
Related Question