Unusual Electron Correlations in Na<sub>x</sub>CoO<sub>2</sub>Due to the Spin-State Quasidegeneracy of Cobalt Ions
Unusual Electron Correlations in Na<sub>x</sub>CoO<sub>2</sub>Due to the Spin-State Quasidegeneracy of Cobalt Ions
Recent studies exposed many remarkable properties of layered cobaltates NaxCoO2. Surprisingly, many-body effects have been found to increase at sodium-rich compositions of NaxCoO2 where one expects a simple, nearly free motion of the dilute S=1/2 holes doped into a band insulator NaCoO2. Here we discuss the origin of enigmatic correlations …