Position operators and wavefunctions

jeudi 29 mai 2014

1. The problem statement, all variables and given/known data



Find the eigenfunctions and the eigenvalues of the following Hamiltonian

[itex]\hat{H} = \frac{1}{2m} \left ( \frac{ \hbar}{i} \vec{\nabla}-\frac{q}{c}(0, B_z x,0) \right ) ^2 = \frac{1}{2m} \left ( - \hbar^2 \vec{\nabla}^2-\frac{\hbar q}{ic}(\vec{\nabla}·(0, B_z\hat{x},0) + (0,B_z x, 0)·\vec{\nabla}) +\left(\frac{q}{c}\right)^2(0, B_z x,0)^2\right ) ^2 = [/itex]



Assume the wavefunction is of the form [itex]\Psi(x) = e ^{i(k_y y + k_z z)}\chi(x)[/itex]

2. Relevant equations



The time dependent Schrodinger Equation:

[itex]\hat{H} \psi(x) = E \psi (x)[/itex]



3. The attempt at a solution

Computing the scalar products we obtain:

[itex]\hat{H} =\frac{1}{2m} \left ( - \hbar^2 \vec{\nabla}^2-\frac{q}{c}B_z x \frac{\hbar \partial}{i \partial y} + \left(\frac{q}{c}B_z x\right)^2 \right ) ^2 [/itex]



And we can rewrite [itex]\frac{\hbar \partial}{i \partial y}[/itex] as [itex]\hat{p} _y[/itex], so:

[itex]\hat{H} =\frac{1}{2m} \left ( - \hbar^2 \vec{\nabla}^2-\frac{q}{c}B_z x \hat{p}_y + \left(\frac{q}{c}B_z x\right)^2 \right ) ^2 [/itex]



Next I state the time-dependent Shcrodinger Equation:

[itex]\frac{-\hbar ^2}{2m}\vec{\nabla}^2\psi-\frac{q}{2mc}B_z\hat{x}\hat{p}_y \psi+\frac{1}{2m}\left (\frac{q}{c} B_z \hat{x}\right)^2 \psi = E \psi[/itex]



The x that appears along in the Bz term: is it the position operator or an scalar operator with the value x? If its the position operator how does it interact with the wavefunction?





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