Anomalous state sandwiched between Fermi liquid and charge ordered Mott-insulating phases of Ti4O7.
The Magnéli phase Ti(4)O(7) exhibits two sharp jumps in resistivity with coupled structural transitions as a function of temperature at T(c1) approximately 142 K and T(c2) = 154 K. 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 T(c2). The low temperature phase below T(c1) shows a clear insulating gap of approximately 100 meV. The intermediate phase between T(c1) and T(c2) 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 Ti(4)O(7).
Taguchi
M
M
Soft X-ray Spectroscopy Lab, RIKEN SPring-8 Center, Sayo, Sayo, Hyogo 679-5148, Japan.
Chainani
A
A
Matsunami
M
M
Eguchi
R
R
Takata
Y
Y
Yabashi
M
M
Tamasaku
K
K
Nishino
Y
Y
Ishikawa
T
T
Tsuda
S
S
Watanabe
S
S
Chen
C-T
CT
Senba
Y
Y
Ohashi
H
H
Fujiwara
K
K
Nakamura
Y
Y
Takagi
H
H
Shin
S
S