Best way to align my equations

Question

I'm trying to align my equations so that the align takes up a fresh line. My code at the moment is

\begin{align}
\frac{d}{d x_3}(|\hat R(\omega,x_3)|^2 + |\hat T(\omega,x_3)|^2) &= \frac{d\hat R}{d x_3}\overline{\hat R} + \frac{d \overline {\hat R}}{d x_3}\hat R + \frac{d \hat T}{d x_3} \overline {\hat T} + \frac{d \overline {\hat T}}{d x_3}\hat T \\ \nonumber
&+ \hat R \overline{\hat R}(\Delta_{4}-\Delta_1)-\hat{R}^2\overline{\hat R} \Delta_2+\overline{\hat R}\Delta_3 \\ \nonumber
&+\hat R \overline{\hat R}(\overline{\Delta_4}-\overline{\Delta_1})-\overline{\hat R}^2\hat{R} \overline{\Delta_2}+\hat R \overline{\Delta_3} \\ \nonumber
&- \hat T \overline{\hat T}(\Delta_1+\Delta_2\hat R) \\ \nonumber
&- \hat T \overline{\hat T}(\overline{\Delta_1}+\overline{\Delta_2}\overline{\hat R}). \\ \nonumber
\end{align}

How can I align this such that the right hand side starts under the derivative? I want to fill the page better. Thanks in advance.

Answer 1

Add a \phantom{={}} from the second line on. Unrelated: I took the liberty to modify some layout details, as I think the \overline should not be above the indices.

\documentclass{article}
\usepackage{mathtools}

\begin{document}

\begin{align}
\frac{d}{d x_3}\bigl(|\hat R(\omega,x_3)|^2 + |\hat T(\omega,x_3)|^2\bigr) &= \frac{d\hat R}{d x_3}\overline{\hat R} + \frac{d \overline {\hat R}}{d x_3}\hat R + \frac{d \hat T}{d x_3} \overline {\hat T} + \frac{d \overline {\hat T}}{d x_3}\hat T \\ \nonumber
&\phantom{={}}+ \hat R \overline{\hat R}(\Delta_{4}-\Delta_1)-\hat{R}^2\overline{\hat R} \Delta_2+\overline{\hat R}\Delta_3 \\ \nonumber
&\phantom{={}}+\hat R \overline{\hat R}(\overline{\Delta}_4-\overline{\Delta}_1)-\overline{\hat R}^2\hat{R} \overline{\Delta}_2+\hat R \overline{\Delta}_3 \\ \nonumber
&\phantom{={}}- \hat T \overline{\hat T}(\Delta_1+\Delta_2\hat R) \\ \nonumber
&\phantom{={}}- \hat T \overline{\hat T}(\overline{\Delta}_1+\overline{\Delta}_2\overline{\hat R}). \\ \nonumber
\end{align}

\end{document}