Tikz：在轴环境内将箭头绘制为节点

Question

是的，我知道有一个类似问题，但我需要一些最简单的东西。我想重现这幅图，我的想法是将两个箭头（对应于 m=+1/2 和 m=-1/2 的箭头）绘制为两个节点，然后将单词报告为节点的节点。我怎样才能将两个节点绘制为箭头？

\documentclass[12pt]{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[full]{textcomp}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,
                positioning}

\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}[
    >={Stealth}
    ]
    \begin{axis}[
            grid=none,
            xticklabel style={rotate=90, anchor=near xticklabel},
            ymin=0,ymax=100,
            xmin=0,xmax=100,
            ticks=none,
            axis lines = middle,
            %y axis line style = {stealth-},
            width=7cm,
            height=7cm,
            set layers,
            x label style={at={(1,0)},right},
            y label style={at={(0,1)},above},
            xlabel={$B_0$},ylabel={$E$},
            style={thick}
        ]
        \addplot [blue,dotted,very thick,domain=0:80] {+0.4*x + 50};
        \addplot [blue,dotted,very thick,domain=0:80] {-0.4*x + 50};
        \draw[<->] (65,76) -- (65,24) node [midway, left] {$\Delta E$};
    \end{axis}
\end{tikzpicture}

\end{document}

Answer 1

另一种方法是使用非常小的 MWE：

\documentclass[12pt]{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}

\usepackage{nccmath}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\usetikzlibrary{arrows.meta,
                positioning}

\begin{document}
    \begin{tikzpicture}[
         > = Stealth,
lbl/.style = {font=\footnotesize, text=black, right}
                        ]
\begin{axis}[
    width=7cm,
    height=8cm,
    axis lines = left,
    xmin=0, xmax=120,
    ymin=0, ymax=100,
    ticks=none,
    xlabel={$B_0$}, ylabel={$E$},
    no marks,
    samples=2,  domain=0:75,
every axis plot post/.append style={blue, very thick, densely dotted},
        ]
\addplot    {+0.4*x + 50} node[lbl]  {$\left\downarrow m = -\mfrac{1}{2}\right.$};
\addplot    {-0.4*x + 50} node[lbl]  {$\left\uparrow   m =  \mfrac{1}{2}\right.$};

\draw[<->] (65,76) --  node [lbl] {$\Delta E$} (65,24);
\end{axis}
    \end{tikzpicture}
\end{document}