Update 7_tight_binding_model_solutions.md - plot fix 2

docs/7_tight_binding_model_solutions.md

@@ -135,7 +135,7 @@ $$
 m^* = \frac{\hbar^2}{2a^2}\frac{1}{t\cos(ka)+4t'\cos(2ka)}
 $$
 
-Plot for t=t':
+Plot for $t=t'$:
 
 ```python
 k1 = np.linspace(-pi, -pi/2-0.01, 300);
@@ -171,7 +171,7 @@ pyplot.xlabel('$k$'); pyplot.ylabel('$m_{eff}(k)$');
 pyplot.xticks([-pi,0,pi],[r'$-\pi/a$',0,r'$\pi/a$']);
 pyplot.yticks([0],[]);
 pyplot.tight_layout();
-
+pyplot.ylim(-3,3)
 pyplot.plot(k1, m(k1,4),'r');
 pyplot.plot(k2, m(k2,4),'r');
 pyplot.plot(k3, m(k3,4),'r',label='t=4t\'');