# Mesoscopic physics > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Mesoscopic_physics > Markdown URL: https://mediated.wiki/source/Mesoscopic_physics.md > Source: https://en.wikipedia.org/wiki/Mesoscopic_physics > Source revision: 1339010078 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Subdiscipline of condensed matter physics This article is about the sub-discipline of condensed matter physics. For the branch of meteorology, see [mesoscale meteorology](/source/Mesoscale_meteorology). Condensed matter physics Phases Phase transition QCP States of matter Solid Liquid Gas Plasma Bose–Einstein condensate Bose gas Fermionic condensate Fermi gas Fermi liquid Supersolid Superfluidity Luttinger liquid Time crystal Phase phenomena Order parameter Phase transition QCP Electronic phases Electronic band structure Plasma Insulator Mott insulator Semiconductor Semimetal Conductor Superconductor Thermoelectric Piezoelectric Ferroelectric Topological insulator Spin gapless semiconductor Electronic phenomena Quantum Hall effect Spin Hall effect Kondo effect Magnetic phases Diamagnet Superdiamagnet Paramagnet Superparamagnet Ferromagnet Antiferromagnet Metamagnet Spin glass Quasiparticles Phonon Exciton Plasmon Polariton Polaron Magnon Roton Soft matter Amorphous solid Colloid Granular material Liquid crystal Polymer Scientists Van der Waals Onnes von Laue Bragg Debye Bloch Onsager Mott Peierls Landau Luttinger Anderson Van Vleck Hubbard Shockley Bardeen Cooper Schrieffer Josephson Louis Néel Esaki Giaever Kohn Kadanoff Fisher Wilson von Klitzing Binnig Rohrer Bednorz Müller Laughlin Störmer Yang Tsui Abrikosov Ginzburg Leggett Parisi Wetterich Perdew Physics portal Category v t e **Mesoscopic physics** is a subdiscipline of [condensed matter physics](/source/Condensed_matter_physics) that deals with materials of an intermediate size. These materials range in size between the [nanoscale](/source/Nanoscopic_scale) for a quantity of [atoms](/source/Atom) (such as a [molecule](/source/Molecule)) and of materials measuring [micrometres](/source/Micrometre).[1] The lower limit can also be defined as being the size of individual atoms. At the [microscopic scale](/source/Microscopic_scale) are bulk materials. Both mesoscopic and [macroscopic](/source/Macroscopic_scale) objects contain many atoms. Whereas average properties derived from constituent materials describe macroscopic objects, as they usually obey the laws of [classical mechanics](/source/Classical_mechanics), a mesoscopic object, by contrast, is affected by thermal fluctuations around the average, and its electronic behavior may require modeling at the level of [quantum mechanics](/source/Quantum_mechanics).[2][3] A macroscopic electronic device, when scaled down to a meso-size, starts revealing quantum mechanical properties. For example, at the macroscopic level the [conductance](/source/Electrical_conductance) of a wire increases continuously with its diameter. However, at the mesoscopic level, the wire's conductance is [quantized](/source/Quantization_(physics)): the increases occur in discrete, or individual, whole steps. During research, mesoscopic devices are constructed, measured and observed [experimentally](/source/Experiment) and [theoretically](/source/Theoretical) in order to advance understanding of the [physics](/source/Physics) of [insulators](/source/Insulator_(electrical)), [semiconductors](/source/Semiconductor), [metals](/source/Metal), and [superconductors](/source/Superconductor). The applied science of mesoscopic physics deals with the potential of building nanodevices. Mesoscopic physics also addresses fundamental practical problems which occur when a macroscopic object is miniaturized, as with the miniaturization of [transistors](/source/Transistor) in semiconductor electronics. The mechanical, chemical, and electronic properties of materials change as their size approaches the nanoscale, where the percentage of atoms at the surface of the material becomes significant. For bulk materials larger than one micrometre, the percentage of atoms at the surface is insignificant in relation to the number of atoms in the entire material. The subdiscipline has dealt primarily with artificial structures of metal or semiconducting material which have been fabricated by the techniques employed for producing [microelectronic](/source/Microelectronic) circuits.[2][3] There is no rigid definition for *mesoscopic physics* but the systems studied are normally in the range of 100 nm (the size of a typical [virus](/source/Virus)) to 1 000 nm (the size of a typical bacterium): 100 nanometers is the approximate upper limit for a [nanoparticle](/source/Nanoparticle). Thus, mesoscopic physics has a close connection to the fields of [nanofabrication](/source/Nanofabrication) and [nanotechnology](/source/Nanotechnology). Devices used in nanotechnology are examples of mesoscopic systems. Three categories of new electronic phenomena in such systems are interference effects, quantum confinement effects and charging effects.[2][3] ## Ballistic conduction In mesoscopic physics, materials are of intermediate size between the microscopic and macroscopic scales. As a result, the nature of electronic transport depends critically on the distance to be crossed by the carriers ( L {\displaystyle L} ) compared to the [mean free path](/source/Mean_free_path) ( L m {\displaystyle L_{m}} ) of the charge carriers. In the diffusive case, where L ≈ L m {\displaystyle L\approx L_{m}} and carriers undergo multiple scattering events, transport is described by the semiclassical [Boltzmann transport equation](/source/Boltzmann_equation). In contrast, when L < L m {\displaystyle L