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Spontaneous symmetry breaking is also associated with phase transitions. For example in the Ising model , as the temperature of the system falls below the critical temperature the Z 2 {\displaystyle \mathbb {Z} _{2}} symmetry of the vacuum is broken, giving a phase transition of the system.
In optimally doped cuprates and iron-based superconductors, the normal state above the critical temperature shows signs of non-Fermi liquid behaviour, and is often called a strange metal. In this region of phase diagram, resistivity increases linearly in temperature and the Hall coefficient is found to depend on temperature.
The Jahn–Teller effect (JT effect or JTE) is an important mechanism of spontaneous symmetry breaking in molecular and solid-state systems which has far-reaching consequences in different fields, and is responsible for a variety of phenomena in spectroscopy, stereochemistry, crystal chemistry, molecular and solid-state physics, and materials science.
Symmetry-breaking phase transitions play an important role in cosmology. As the universe expanded and cooled, the vacuum underwent a series of symmetry-breaking phase transitions. For example, the electroweak transition broke the SU(2)×U(1) symmetry of the electroweak field into the U(1) symmetry of the present-day electromagnetic field.
Consider a system that breaks some symmetry below a phase transition, which is characterized by an order parameter . This order parameter is a measure of the order before and after a phase transition; the order parameter is often zero above some critical temperature and non-zero below the critical temperature.
Charge ordering (CO) is a (first- or second-order) phase transition occurring mostly in strongly correlated materials such as transition metal oxides or organic conductors. Due to the strong interaction between electrons, charges are localized on different sites leading to a disproportionation and an ordered superlattice.
Derivative works of this file: Pure iron phase diagram (EN).png This is a retouched picture , which means that it has been digitally altered from its original version. The original can be viewed here: Diagramma di fase del ferro puro.svg : .
Low-pressure phase diagram of pure iron. BCC is body centered cubic and FCC is face-centered cubic. Iron-carbon eutectic phase diagram, showing various forms of Fe x C y substances. Iron allotropes, showing the differences in structure. The alpha iron (α-Fe) is a body-centered cubic (BCC) and the gamma iron (γ-Fe) is a face-centered cubic (FCC).