Learning goals
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@@ -8,24 +8,17 @@ from common import draw_classic_axes, configure_plotting
@@ -8,24 +8,17 @@ from common import draw_classic_axes, configure_plotting
- how Drude theory predicts the generation of a 'Hall voltage' for electrons moving through a conductor in an electric and a magnetic field.
- how to calculate the electron density of states in 1D, 2D, and 3D using the Sommerfeld free-electron model.
- how to express the total number and energy of particles in a system in terms of an integral over k-space.
Ohm's law states that $V=IR=I\rho\frac{l}{A}$. In this lecture we will investigate where this law comes from. We will use the theory developed by Paul Drude in 1900, which is based on three assumptions:
@@ -93,6 +86,18 @@ where $R_{\rm H}=-\frac{1}{ne}$ is the _Hall resistance_. So by measuring the Ha
@@ -93,6 +86,18 @@ where $R_{\rm H}=-\frac{1}{ne}$ is the _Hall resistance_. So by measuring the Ha
While most materials have $R_{\rm H}>0$, interestingly some materials are found to have $R_{\rm H}<0$. This would imply that the charge carriers either have a positive charge, or a negative mass. We will see later (chapter 17) how to interpret this.
Atoms in a metal provide conduction electrons from their outer shells (often s-shells). These can be described as waves in the crystal, analogous to phonons. Hamiltonian of a free electron: