Search results
Results from the WOW.Com Content Network
Bloch's theorem — For electrons in a perfect crystal, there is a basis of wave functions with the following two properties: each of these wave functions is an energy eigenstate,
Using Bloch's theorem, we only need to find a solution for a single period, make sure it is continuous and smooth, and to make sure the function u(x) is also continuous and smooth. Considering a single period of the potential: We have two regions here. We will solve for each independently: Let E be an energy value above the well (E>0)
Bloch's theorem was inspired by the following theorem of Georges Valiron: Theorem. If f is a non-constant entire function then there exist disks D of arbitrarily large radius and analytic functions φ in D such that f(φ(z)) = z for z in D. Bloch's theorem corresponds to Valiron's theorem via the so-called Bloch's principle.
The Bloch states ψ k (r) are defined as the eigenfunctions of a particular Hamiltonian, and are therefore defined only up to an overall phase. By applying a phase transformation e iθ ( k ) to the functions ψ k ( r ), for any (real) function θ ( k ), one arrives at an equally valid choice.
The Bloch's function is an exact eigensolution for the wave function of an electron in a periodic crystal potential corresponding to an energy (), and is spread over the entire crystal volume. Using the Fourier transform analysis, a spatially localized wave function for the m -th energy band can be constructed from multiple Bloch's functions:
The solutions in this case are known as Bloch states. Since Bloch's theorem applies only to periodic potentials, and since unceasing random movements of atoms in a crystal disrupt periodicity, this use of Bloch's theorem is only an approximation, but it has proven to be a tremendously valuable approximation, without which most solid-state ...
The book covers a wide range of topics in solid state physics, including Bloch's theorem, crystals, magnetism, phonons, Fermi gases, magnetic resonance, and surface physics. The chapters are broken into sections that highlight the topics. [5]
Bloch's theorem allows a full characterization of the wave propagation properties of a material by assigning a matrix to each wave vector in the Brillouin zone. Mathematically, this assignment creates a vector bundle. Different materials will have different wave propagation properties, and thus different vector bundles.