Quantum Charge Liquid - a new metallic state in 2 dimensions ? Application to Na${}_{0.7}$CoO${}_2$ family

Abstract

`Quantum Charge Liquid'(QCL), a new phase, is proposed to describe anomalous metallic properties (T < 100 K)of a density 'y' of doped holes with strong coulomb repulsions, in a band insulator NaCoO${}_2$ with N sites. This phase, a quantum melted charge order, is characterized by a `charge only' fermi-sea (cFS) of yN charges and a `soft spin-liquid' of yN spin-\half moments forming an `effective lattice' of Heisenberg antiferromagnet. An approximate microscopic theory and some consequences are outlined. Anomalous `Fermi surfaces' seen in ARPES of \ncob and \n7cob matches well with our cFS, rather than a corresponding single band free electron FS.

4 pages of LaTeX, 2 figure EPS files, one PS file