# How to plot rectangular potential in matlab

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Pouyan Msgn on 8 Nov 2018
Commented: Star Strider on 8 Nov 2018
I will try to plot something like this : Observ that this is a rectangular potential barrier, the dashed line is the classical result of the potential U and the blue line is the quantum mechanics. The tunneling regime takes the place at intersection of the dashed line and the blue line; and the tops of the blue line is called the resonance which I have to show. My attempt is
clc
clear all
m=9.11 * 10^(-31);
U=5e-19;
E=0e-19:0.001e-19:12e-19;
a=3e-9;
h=1.36e-34;
k=sqrt(2*m.*(U-E));
k2=k/h;
c=(U^2)*(sinh(0.5*a*k2).^2)./(4*E.*(U-E));
T=1./(1+c);
plot(E,T)
But how can I get a plot like this ?

Star Strider on 8 Nov 2018
Your code appears to be correct. If you want the labels, try this:
m=9.11E-31;
U=5e-19;
E=0e-19:0.001e-19:12e-19;
a=3e-9;
h=1.36e-34;
k=sqrt(2*m.*(U-E));
k2=k/h;
c=(U^2)*(sinh(0.5*a*k2).^2)./(4*E.*(U-E));
T=1./(1+c);
[respks, locs] = findpeaks(T);
figure
plot(E,T)
hold on
plot([0.5 0.5]*1E-18, ylim, '--r')
hold off
text(E(locs+275), respks*0.99, compose('\\bf{\\leftarrow res %d}', 1:3), 'HorizontalAlignment','left', 'VerticalAlignment','top', 'Rotation', -75)
text(0.5E-18, 0.1, sprintf('\\bftunneling \\rightarrow'), 'HorizontalAlignment','right')
Experiment to get the result you want.
Star Strider on 8 Nov 2018
As always, my pleasure!