Landau-level mixing and its effects in physics and wave function

Question

We know the Landau levels are energy levels caused by external magnetic fields and the results in quantization of energy levels. Its wave function is well-known: https://en.wikipedia.org/wiki/Landau_quantization

My question here is:

1) what causes Landau-level mixing,

2) its effects in physics and

3) wave function deviated from the usual Landau levels wave functions.

4) relations to fractional quantum Hall effects or beyond.

This post imported from StackExchange Physics at 2020-11-26 15:41 (UTC), posted by SE-user annie marie heart

Comments

The first, and perhaps the third question is answerable on this site, but questions 2 and 4 are extremely broad and books have been written on the topic. Please make a narrow, focused question.

This post imported from StackExchange Physics at 2020-11-26 15:41 (UTC), posted by SE-user Marius Ladegård Meyer