Measurement of the femtosecond optical absorption of LaAlO3/SrTiO3 heterostructures: evidence for an extremely slow electron relaxation at the interface.
The photocarrier relaxation dynamics of an n-type LaAlO3/SrTiO3 heterointerface is investigated using femtosecond transient absorption (TA) spectroscopy at low temperatures. In both LaAlO3/SrTiO3 heterostructures and electron-doped SrTiO3 bulk crystals, the TA spectrum shows a Drude-like free carrier absorption immediately after excitation. In addition, a broad absorption band gradually appears within 40 ps, which corresponds to the energy relaxation of photoexcited free electrons into self-trapped polaron states. We reveal that the polaron formation time is enhanced considerably at the LaAlO3/SrTiO3 heterointerface as compared to bulk crystals. Further, we discuss the interface effects on the electron relaxation dynamics in conjunction with the splitting of the t2g subbands due to the interface potential.
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Yasuhiro
Y
Yamada
Hiroki K
HK
Sato
Yasuyuki
Y
Hikita
Harold Y
HY
Hwang
Yoshihiko
Y
Kanemitsu