\documentclass{standalone}
\input{palette}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.15}
\usepgfplotslibrary{colormaps}
\usepgfplotslibrary{groupplots} 
\sffamily
\pgfplotsset{colormap/jet}

\begin{document}
	\begin{tikzpicture}
	\def\yPosRel{\pgfkeysvalueof{/pgfplots/ymax}*.85}
	\def\xLeftPosRel{-0.03*\pgfkeysvalueof{/pgfplots/xmax}}
	\def\xRightPosRel{\pgfkeysvalueof{/pgfplots/xmax}*.96}
	
	\begin{groupplot}[view={0}{90},
	xlabel=$k$,
	ylabel={$\hbar \omega$ (meV)},
	ylabel style = {yshift=-0.1cm},
	xmin=0,
	ymin=0,
	ymax=0.69,
	height=4cm,
	point meta min=0,
	point meta max=1,
	group/xlabels at = edge bottom,
	group style = {group size = 3 by 1,	%cols by rows
		horizontal sep=0.1cm,
		vertical sep=0.1cm,
		xlabels at = edge bottom
	}]
	
	%%% Row 1
	\nextgroupplot[title={$P_x$}, title style = {at = {(axis description cs:0.5,.9)}}, 
	xtick = {0,1.5708,3.14159,4.7123889,6.28318},
	xticklabels = {0,$\frac{\pi}{2}$,$\pi$,$\frac{3\pi}{2}$,},
	ytick={0.0,0.25,0.5},
	yticklabels={0.0,,0.5},
	yticklabel style = {/pgf/number format/fixed, /pgf/number format/zerofill, /pgf/number format/precision=1, },
	enlargelimits=false,
	axis on top,
	colorbar horizontal, 
	every colorbar/.append style={
		at={(0,1.45)},anchor=north west,
		width=
		3*\pgfkeysvalueof{/pgfplots/parent axis width}+
		2*\pgfkeysvalueof{/pgfplots/group/horizontal sep},
		xlabel={Value},
		xlabel near ticks,
		xtick={0,0.25,0.5,0.75,1},
		xticklabels = {$0$,$0.25$,$0.5$,$0.75$,$1$},
		axis on top,
		xtick pos=top,
		xticklabel pos=top,
		xticklabel style={
			/pgf/number format/.cd,
			fixed,
			precision=2,
			fixed zerofill,
		}
	}]
	\addplot [matrix plot*,point meta=explicit] table [meta index={2}] {PolarizationFactors/Px.pgfplots};
	\node [color=black, anchor=west] at ($(\xLeftPosRel,\yPosRel)$) {(a)};
	
	
	\nextgroupplot[title={$P_y$}, title style = {at = {(axis description cs:0.5,0.9)}},
	enlargelimits=false,
	axis on top,
	xtick = {0,1.5708,3.14159,4.7123889,6.28318},
	xticklabels = {0,$\frac{\pi}{2}$,$\pi$,$\frac{3\pi}{2}$,},
	ytick={0.0,0.25,0.5},
	yticklabels = {,,},
	ylabel={}]
	\addplot [matrix plot*,point meta=explicit] table [meta index={2}] {PolarizationFactors/Py.pgfplots};
	\node [color=black, anchor=west] at ($(\xLeftPosRel,\yPosRel)$) {(b)};
		
	
	\nextgroupplot[title={$P_z$}, title style = {at = {(axis description cs:0.5,0.9)}},
	enlargelimits=false,
	axis on top,
	xtick = {0,1.5708,3.14159,4.7123889,6.28318},
	xticklabels = {0,$\frac{\pi}{2}$,$\pi$,$\frac{3\pi}{2}$,},
	ytick={0.0,0.25,0.5},
	yticklabels = {,,},
	ylabel={}]
	\addplot [matrix plot*,point meta=explicit] table [meta index={2}] {PolarizationFactors/Pz.pgfplots};
	\node [color=black, anchor=west] at ($(\xLeftPosRel,\yPosRel)$) {(c)};
	
	
	\end{groupplot}
	\end{tikzpicture}
\end{document}
