Center for Correlated Electron Systems

Seminar

Direct observation of crystallographic symmetry of compressively strained SrRuO3 thin films

July 20, 2020l Hit 1130
Date : July 22, 2020 15:00 ~ 16:30
Speaker : Dr. Chang Jae Roh (GIST)
Location : https://snu-ac-kr.zoom.us/j/8095910475

SrRuO3 (SRO) is one of the famous materials in condensed matter physics society because it has intriguing physical properties, such as itinerant ferromagnetism, high electrical conductivity. Moreover, thin film form SRO has recently been received large attention with their correlation effect that originated from spin-polarized electron. However, there is a lack of understanding of SRO films of in symmetric perspective. In this talk, I will present the crystallographic symmetry of SRO films grown on SrTiO3 (001) substrate via optical second harmonic generation (SHG) technique. First, I will discuss surface/interface and inner-bulk symmetry of SRO films. With increasing the film thickness for t=4, 10, 30, 50, 70, 90, and 250 nm, the crystallographic symmetry of SRO films varies from tetragonal to distorted monoclinic symmetry according to their structure. Particularly, the practical direction of inversion symmetry breaking of surface rotates from the out-of-plane direction for thinner films to the in-plane direction for thicker films during the variation. Second, I will present the inversion symmetry breaking in SRO films stabilized by oxygen octahedral network relaxation. Together with SHG and scanning transmission electron microscopy (STEM) technique, it is demonstrated that clear evidence of a phase separation into the strained tetragonal and distorted orthorhombic phases in single-crystalline SRO films, and in particular the ferromagnetic polar metal phase formed between the tetragonal and orthorhombic phases.

 

 

Host : Prof. Tae Won Noh