Peierlsövergången

Peierlsövergången, also known as the Peierls transition, is a phenomenon in condensed matter physics observed in one-dimensional conductors. It describes a spontaneous distortion of the atomic lattice that leads to a metal-insulator transition. In a 1D system, electrons can easily form a density wave that pairs up adjacent atoms. This pairing lowers the energy of the system by opening an energy gap at the Fermi level, the energy level of the highest occupied electrons in a metal.

The transition occurs when the temperature drops below a critical point, the Peierls transition temperature. Below this temperature, the lattice distorts, and the material becomes an insulator or a semiconductor because the energy gap prevents electrons from moving freely. Above the transition temperature, the lattice is in its undistorted state, and the material behaves as a metal. This effect is particularly prominent in materials with a linear chain of atoms, where electron-phonon interactions are strong.

The Peierls transition has important implications for understanding the electronic properties of low-dimensional materials. It explains why some quasi-one-dimensional materials, which are expected to be metallic based on their band structure, are actually insulators at low temperatures. The presence of the Peierls distortion can significantly alter the conductivity and other physical properties of these materials, making them of interest for applications in fields like organic electronics and novel electronic devices. Experimental evidence for the Peierls transition has been observed in various materials, including organic conductors and some inorganic chain compounds.