\documentclass{article}
\usepackage{threeparttable}
\usepackage{multirow}
\usepackage{booktabs}
\usepackage{xcolor}
\usepackage{tikz}
\begin{document}
\begin{table}[!ht]
\setlength\tabcolsep{0pt}
\centering
\begin{threeparttable}
\begin{tabular}{@{\extracolsep{2ex}}*{2}{cc}}
\toprule
1.41 & 1.24e7 \\
1.06e8 & 0.00111 \\
1.23 \& 0.00123 & \begin{tabular}{@{}c@{}}1.23 \\ 0.00123\end{tabular} \\
\bottomrule
\end{tabular}
\end{threeparttable}
\end{table}
\end{document}