The Magnéli phase Ti4O7 exhibits two sharp jumps in resistivity with coupled structural transitions as a function of temperature at Tc1∼142K and Tc2=154K. We have studied electronic structure changes across the two transitions using 7 eV laser, soft x-ray, and hard x-ray (HX) photoemission spectroscopy (PES). Ti 2p-3d resonant PES and HX PES show a clear metallic Fermi edge and mixed valency above Tc2. The low temperature phase below Tc1 shows a clear insulating gap of ∼100meV. The intermediate phase between Tc1 and Tc2 indicates a pseudogap coexisting with remnant coherent states. HX PES and complementary calculations have confirmed the coherent screening in the strongly correlated intermediate phase. The results suggest the existence of a highly anomalous state sandwiched between the mixed-valent Fermi liquid and charge ordered Mott-insulating phase in Ti4O7.
ASJC Scopus subject areas
- Physics and Astronomy(all)