# Study Guide:Mathematical Mesoscopic Physics/What is Mesoscopic Physics

## Meaning of the name "Mesoscopic Physics"[edit]

"Meso" refers to length scales intermediate between microscopic (single atoms) and macroscopic scales (where the usual classical, bulk behaviour takes over). This regime was first identified as interesting in the study of phase transitions, where new phenomena occur when the correlation length of fluctuations becomes similar to the system size. Later, the development of small (micrometer sized) metallic or semiconducting structures in the computer industry prompted researchers to ask what happens when electrons move in these small spaces. Three effects become crucial:

**Fluctuations**(of charge, current, resistance etc.) become important, since 'self-averaging' is less effective if there are only a small number of particles**Interactions**become more important, as the Coulomb repulsion in these tightly confined spaces may overwhelm the thermal energy at sufficiently low energies**Quantum interference**effects show up, and can be used to realize devices such as interferometers

Often, one has to deal with the interplay of all three of these phenomena. Quantum mechanics and statistical averaging procedures are important ingredients in describing such "mesoscopic systems". --FlorianMarquardt 12:30, 31 August 2008 (UTC)

## A brief history of the field[edit]

(Describe some highlights in chronological order)