High-temperature symmetry breaking in the electronic band structure of thequasi-one-dimensional solid NbSe3 - art. no. 196403

The electronic band structure of the Peierls compound NbSe3 has been explor ed for its symmetries with microspot synchrotron photoemission. The Fermi l evel crossings and deviations from one-dimensional behavior are identified. Density-functional calculations of the Fermi surfaces confirm the nesting conditions relevant for the two phase transitions. The instability along th e chains with superstructure periodicity q = 0.44 Angstrom (-1) induces a b ackfolding of the electronic bands, and the Fermi level crossings appear su ppressed. This broken symmetry is observed in the fluctuation regime at mor e than twice the critical temperature, where the correlation length is stro ngly reduced.