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Interacting electrons confined strictly to one dimension display a quantum-critical non-Fermi liquid state known as the Luttinger liquid (LL). The sliding Luttinger liquid (SLL) is a recent theoretical scenario [1] for stabilizing LL behavior against the charge density wave (CDW) formation that would be expected in a system of coupled one-dimensional chains. This new state of matter, which can be unstable to novel superconductivity, has not thus far been identified in known quasi-one dimensional (quasi-1d) crystals. Li0.9Mo6O17 is a quasi-1d metal for which the temperature (T) dependence of the resistivity shows a minimum around TX 24K, and then rises as T decreases below TX, a possible sign of CDW gap opening. Slightly above TX there is a weak broad specific heat anomaly. However the magnetic susceptibility is always temperature independent and below TX no gap is seen in optical spectroscopy. X-ray diffraction has never found evidence for density wave formation. Below 1.8K Li0.9Mo6O17 is a superconductor. Well above TX, our past studies [2] by angle resolved photoemission spectroscopy (ARPES) have demonstrated a 1d Fermi surface defined by dispersing excitations whose ARPES lineshapes are described by LL theory, with a power law onset at the Fermi energy in the angle integrated spectrum. Our [3] most recent T-dependent ARPES studies find quantum criticality and an anomalous dimension that renormalizes downward with decreasing T. We [3] attempt a unified interpretation of all these various transport and spectral properties, within the general framework of the SLL scenario but including the crucial role of two-band intra-chain interactions, treated by the renormalization group.
[1] V. J. Emery, E. Fradkin, S. A. Kivelson, and T. C. Lubensky, Phys. Rev. Lett. 85, 2160 (2000). [2] G.-H. Gweon, J. W. Allen and J. D. Denlinger, Phys. Rev. B 68, 195117 (2003). [3] Coworkers: J. V. Alvarez, Feng Wang, S.-K. Mo, (U. Mich), G.-H. Gweon (LBNL), J. He, R. Jin, D. Mandrus (ORNL) and H. Höchst (SRC, U. Wisc.) *Work supported at UM by U.S. NSF under Grant No. DMR-03-02825 |