IAMS lecture on April 28, 10:00-11:00am, Dr. Poe Lecture Hall, Dr. Te-Yu Chien

IAMS Lecture Announcement


Title: Low Dimensional Electronic Properties Studied in Real and in Reciprocal Space

Speaker: Dr. Te-Yu Chien 簡德宇博士

Advanced Photon Source , Argonne National Laboratory

Time: 10:00-11:00, April 28, 2011

Place: Dr. Poe Lecture Hall, IAMS (本所浦大邦講堂 台大校園內)

Host: Dr. Jer-Lai Kuo 郭哲來博士


Dimensionality could affect material properties greatly due to spatially confinement environment and/or translational broken symmetry. Examples could be found when creating surfaces of materials. One of the most famous examples is the 7x7 surface structural reconstruction on the Si (111) surface [1]. Surface electronic reconstruction was also observed on Ca1.9Sr0.1RuO4 surface [2]. It was also found that the electron-phonon coupling on Be(0001) surface is much more stronger than its bulk counterpart [3]. When depositing another material on the clean surfaces, the interfaces are then created. In addition to the two dimensional environment as the surfaces have, chemical modification at interfaces offers extra degree of freedom for controlling the properties. Examples could be seen in the recent two-dimensional highly mobile electron gas found at LaAlO3/SrTiO3 interfaces [4], and in the orbital reconstruction at YBCO/LCMO interfaces [5].

To fully understand the electronic properties in low dimension, the information in real and in reciprocal spaces is needed. For interface information, the length scale of the region of the interest is confined within few nm at interface. Scanning tunneling microscope (STM) could be utilized to acquire the electronic properties at interface in real space. In this talk, I will briefly discuss the recent development of the cross-sectional STM (XSTM) for studying perovskite complex oxide interfaces. Three types of all-oxide interfaces will be discussed: p-n junction; Schottky barrier between metal and n-type semiconductor; and interfaces between superconducting and ferromagnetic materials. On the other hand, the information of band structures could be revealed in reciprocal space by using angle-resolved photoemission spectroscopy (ARPES). I will also talk about how to understand the unusual high electron-phonon coupling on Be(0001) surface, and why the dimensionality matters.


1. G. Binnig et al., Phys. Rev. Lett. 50, 120-123 (1983).

2. R. G. Moore et al., Science 318, 615-619 (2007).

3. TeYu Chien et al., Phys. Rev. B 80, 241416(R) (2009).

4. A. Ohtomo and H. Y. Hwang, Nature 427, 423 (2004).

5. J. Chakhalian et al., Science 318, 1114- 1117 (2007).