Condensed matter physics is the Physics of condensed matter. Below we look at the different broad types of condensed matter. The properties of condensed matter systems depend, among other things, on the chemical composition of the system (see Chemistry), and the physical laws the chemical components obey.
Condensed vs non-condensed
Condensed matter refers to Bulk matter in a condensed form, i.e. one that is composed of condensed phases. Condensed phases include mainly Solid, and Liquid. However, generally, it is a phase for which the particles adhere to each other strongly enough (by for example Intermolecular forces or Chemical bonds) relative to their kinetic energy so that the system remains approximately bound in the absence of external forces, or where the particles are sufficiently highly concentrated so that they interact strongly (for example non-attracting particles can be forced to condense by confining them in a small volume (or by some external force, like gravity), forcing them to be "nearly touching", as in a liquid or solid).
Non-condensed matter has constituents that are barely bound together, if at all, and thus often need to be confined, either naturally, or artificially, to be studied as a whole. The main types are: Gases (see Fluid mechanics), and plasmas.
Solid vs fluid
A Solid is a form of matter that can resist a considerable amount of stress without flowing (so that its only response is elastic).
A Fluid is a form of matter that flows under virtually any amount of stress.
A viscoelastic material displays solid-like elasticity of short time scales, and fluid-like viscosity on long time scales.
There is really a continuum between these. For instance some Rubbers are closer to solids, while others are more clearly viscoelastic, depending on the ratio of elastic to viscous deformation.
Hard vs soft
Solid-state physics studies matter in hard form. Hard forms are characterized by strong inter-particle bonding (often Chemical bonds, when at room temperature). This bonding is strong enough that it makes the relative position of the particles essentially fixed, with thermal fluctuations making particles vibrate only a bit relative to this fixed position. It is also strong enough to resist relatively large external stresses (i.e. it doesn't flow) All forms of hard matter are solids.
Soft matter physics studies matter in other condensed forms (soft forms), where some or all (relative) positional degrees of freedom are "soft", that is, strongly affected by thermal fluctuations, so that they have large variances. It also includes forms with weak bonding so that the material can't resist barely any external stress without flowing. Soft matter can be a solid or a fluid.
Note that given the definition above, one expects an spectrum between the two types of matter, as the definitions involve quantities that can potentially take a continuous of values. Most materials in nature, however, can be classified in one or the other.
One of the most important properties of materials is that they exhibit different phases. These are understood through the study of Phase transitions. See Paul and Lubenski's book Principles of condensed matter physics.
Condensed forms of matter
Hard forms
- Crystalline solids (crystalline symmetry). See Solid-state physics.
- Amorphous solids; in particular glasses (disordered; statistically homogeneous/isotropic, but positions fixed). See discusion in Viscosity and elasticity.
- Nuclear matter.
- Porous solids (see Porous material).
- Many polymers, particularly plastics, are solids.
- Simple liquids (fully homogeneous/isotropic). See Fluid mechanics. The fluid may be a solution, but that only changes it chemical properties, not its physical ones.
- Several types of complex fluids. Main types:
- Solid–liquid (Suspensions (particularly Colloids) and Gels)
- solid–gas (Granular materials, and Fibrous materials)
- liquid–gas (Foams)
- liquid–liquid (Emulsions)
- Liquid crystals: nematic, smectic, cholesteric, columnar, etc.
- Several polymeric materials are soft. E.g. some Plastics, Rubbers, Latex
- Surfactants
- Biological matter
- Many kinds of Active matter and Driven matter.
- Pastes, or soft glassy materials
Non-condensed forms of matter
- simple Gases
- Simple plasmas.
- Quark-gluon plasmas
- Some types of complex fluids are non-condensed phases, for instance Aerosols.
There are also phases of matters that exhibit quantum effects. These are studied (along with other non-quantum phases that nontheless can be understood using quantum mechanics) in Quantum condensed matter physics
Order and disorder designate the presence or absence of some symmetry or correlation in a many-particle system. See Disorder, Disordered system. See here and here, and here
Discussion Meeting: Nonlinear Physics of Disordered Systems: From Amorphous Solids to Complex Flows
See Materials science for the applications of the principles of condensed matter physics to understanding and use of the wealth of materials in the world, both natural, and artificial.
For the study of the physics and chemistry at the interface between two phases, see Surface science.
Strongly correlated systems: From models to materials
http://jakobschwichtenberg.com/understanding-symmetry-breaking-goldstones-theorem-intuitively/