Optical modulation of effective on-site coulomb energy for the Mott transition in an organic dimer insulator.
We report an optical modulation of the effective on-site Coulomb energy U on a dimer (U_{dimer}) for achieving the Mott insulator-to-metal transition in kappa-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br, as investigated by pump-probe spectroscopy. A reduction of U_{dimer} is optically induced by molecule displacement in the dimer under intradimer excitation. The mechanism of this metallization differs greatly from the photodoping-type mechanism reported previously. In contrast, a faster transition via the photodoping mechanism is detected for interdimer excitation. A metallic-domain-wall oscillation originating from the modulation of U_{dimer} was also observed near the critical end point of the Mott transition line.
Department of Physics, Tohoku University, Sendai 980-8578, Japan.
Y
Y
Kawakami
S
S
Iwai
T
T
Fukatsu
M
M
Miura
N
N
Yoneyama
T
T
Sasaki
N
N
Kobayashi