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Li0.9Mo6O17 is a quasi-one dimensional (quasi-1D) material whose single particle spectrum as measured by angle resolved photoemission spectroscopy (ARPES) has features generic to the T-dependent spectral function of the one-band Tomonaga-Luttinger (TL) model. The ARPES spectrum of the dispersing excitation defining its quasi-1D Fermi surface shows a holon (charge mode) peak and a spinon edge dispersing with different velocities, and the k-integrated spectrum approaches the Fermi energy E_F as a power law with anomalous exponent alpha. New Luttinger liquid physics beyond the simple TL model has also been observed. (1) A strong T-dependence of alpha can be traced to renormalization by interacting charge neutral critical modes that emerge naturally for Li0.9Mo6O17 because two nearly degenerate bands cross E_F [1]. (2) The TL spectral function displays perfect quantum critical "E/T" scaling, while the ARPES spectrum shows perfect scaling only for the spinon edge but not for the holon peak. Nonetheless the imperfect scaling can be described by a phenomenological modification of the TL spectral function, which appears to be rooted in interacting charge modes involving either the two-band nature of the material, or the role of the inter-chain coupling, or both.
[1] Feng Wang et al., "New Luttinger-Liquid Physics from Photoemission on Li0.9Mo6O17", Phys. Rev. Lett. 96, 196403 (2006). ** Collaborators: Feng Wang (U. Michigan), J. V. Alvarez (U. Autonoma Madrid), J. He, D. Mandrus (U. Tenn. and ORNL), R. Jin (ORNL), and H. Hoechst (SRC, U. Wisconsin). |
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