Remove left margin from a single {turnpage} page in RevTex class

I have a large plot that I put on a {turnpage} page in a mainly portrait document using RevTex4. As shown in the attached figure below, I was able to hspace*{-2cm} after the rotating command to move it downward on the page. However, when I tried to move the plot toward the left, the trick doesn’t work for vspace{}. I have also tried newenvironment{changemargin} and addtolength{leftmargin}. The result appeared to be compilable but unaffected, so I don’t really know whether the commands were ignored or just didn’t have visible effect due to other reasons…

Thanks for help!!

• Yen-Yung

documentclass[a4paper]{revtex4}

usepackage{graphicx}

usepackage[margin=1cm]{geometry}
begin{document}
    

begin{turnpage}
begin{figure}
includegraphics[width=0.8pageheight,keepaspectratio]{example-image-a} 
end{figure}
end{turnpage}  

end{document}