Temperature-Dependence of Hypersound Dynamics in SrTiO3/SrRuO3 Heterostructures Studied by Ultrafast Spectroscopy
Chi-Yuan Yang (楊濟源)1,2*, A. K. Yadav3, R. Ramesh3, Yu-Chieh Wen (溫昱傑)1, Chia-Hao Hsu (許家豪)1, Maw-Kuen Wu (吳茂昆)1, Chih-Ta Chia (賈至達)4, Kung-Hsuan Lin (林宮玄)1
1Institute of Physics, Academia Sinica, Taipei, Taiwan
2Department of Physics, National Taiwan University, Taipei, Taiwan
3Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
4Department of Physics, National Taiwan Normal University, Taipei, Taiwan
* presenting author:Chi-Yuan Yang, email:lecteryang@yahoo.com.tw
Strontium titanate (SrTiO3, STO) and strontium ruthenate (SrRuO3, SRO) are complex oxide with perovskite structure. Their property, such as thermoelectricity and superconductivity, has been widely investigated for scientific and industrial purposes. Recently, complex oxide heterostructures can be grown by pulsed laser deposition. It opens many possibilities for new properties of materials. With ultrafast pump-probe spectroscopy, we demonstrated that metal-like SRO thin film can be served as a phonon transducer to generate hypersound with frequency of several tens to several hundreads of GHz. This technique can be utilized to study not only the elastic properties of perovskite thin films but also the interfaces. In this study, we used this technique to study the temperature dependence of structural phases in STO. During the crossing over the soft-mode transition in STO around 110 K, the shortening of phonon lifetime were also observed.

Keywords: Strontium titanate, strontium ruthenate, ultrafast pump-probe spectroscopy, phonon transducer