[原分所演講] IAMS Lecture on March 8, 11:00am, Dr. C. T. Chang Memorial Hall, Prof. Chong-Yu Ruan
消息來源：化學系辦公室
截止日期：2016-03-08
IAMS Lecture Announcement
中研院原分所演講公告
Title: Imaging light-induced metastable phases and hidden states in complex electronic materials with femtosecond coherent electron beams
Speaker: Prof. Chong-Yu Ruan
(Department of Physics and Astronomy, Michigan State University)
Time: 11:00 AM, March 8 (Tuesday)
Place: Dr. C. T. Chang Memorial Hall, IAMS (原分所張昭鼎講堂 臺大校園內)
Contact: Dr. Mei-Yin Chou 周美吟所長
Abstract:
Currently the ultrafast electron diffraction has achieved sub-picosecond temporal resolution and atomic resolution. However, direct ultrafast imaging of a nanometer scale specimen through coherent single-particle diffraction has not been achieved largely due to insufficient intensity when tuned to a coherence length that matches the size of the specimen under the projected phase space density. Utilizing a recently implemented high-brightness electron source with flexible optical design, we test the performance of ultrafast electron microdiffraction and coherence imaging. We demonstrate the feasibilities of single-shot microdiffraction on a single micrometer-sized domain in Highly Ordered Pyrolytic Graphite (HOPG) and coherent diffractive imaging of 10 nm scale charge-ordered domain structures in single-crystal complex materials, as validated by the measured brightness at the sample plane. These initial results show that source-limited performance even from a sub-relativistic electron beamline can drastically improve the current performance of ultrafast electron imaging and diffraction.
Using the ultrafast electron imaging techniques, we studied the light-induced phase transitions in transition-metal dichalcogenide and oxides materials. A succession of different phases was introduced transiently using femtosecond mid-infrared pulses and the local atomic scale charge-density-wave dynamics and morphological evolution of the long-range textured domains were in situ characterized using the ultrashort coherent electron pulses. The various metastable and hidden states emerging under the controlled nonthermal, nonadiabatic driving highlight the interaction-driven nature of these transitions with limited involvement of lattice entropy. The methodology introduced here can be generally applied to survey the complex energy landscape in strongly correlated electron systems, avoiding the difficulty of electrostatic gating or confounding effects due to defects and/or disorder. In particular, the observation of robust non-thermal switching at meso-scales and at ultrafast timescales, provides a platform for designing high-speed low-energy consumption nano-photonics and electronics devices.
中研院原分所演講公告
Title: Imaging light-induced metastable phases and hidden states in complex electronic materials with femtosecond coherent electron beams
Speaker: Prof. Chong-Yu Ruan
(Department of Physics and Astronomy, Michigan State University)
Time: 11:00 AM, March 8 (Tuesday)
Place: Dr. C. T. Chang Memorial Hall, IAMS (原分所張昭鼎講堂 臺大校園內)
Contact: Dr. Mei-Yin Chou 周美吟所長
Abstract:
Currently the ultrafast electron diffraction has achieved sub-picosecond temporal resolution and atomic resolution. However, direct ultrafast imaging of a nanometer scale specimen through coherent single-particle diffraction has not been achieved largely due to insufficient intensity when tuned to a coherence length that matches the size of the specimen under the projected phase space density. Utilizing a recently implemented high-brightness electron source with flexible optical design, we test the performance of ultrafast electron microdiffraction and coherence imaging. We demonstrate the feasibilities of single-shot microdiffraction on a single micrometer-sized domain in Highly Ordered Pyrolytic Graphite (HOPG) and coherent diffractive imaging of 10 nm scale charge-ordered domain structures in single-crystal complex materials, as validated by the measured brightness at the sample plane. These initial results show that source-limited performance even from a sub-relativistic electron beamline can drastically improve the current performance of ultrafast electron imaging and diffraction.
Using the ultrafast electron imaging techniques, we studied the light-induced phase transitions in transition-metal dichalcogenide and oxides materials. A succession of different phases was introduced transiently using femtosecond mid-infrared pulses and the local atomic scale charge-density-wave dynamics and morphological evolution of the long-range textured domains were in situ characterized using the ultrashort coherent electron pulses. The various metastable and hidden states emerging under the controlled nonthermal, nonadiabatic driving highlight the interaction-driven nature of these transitions with limited involvement of lattice entropy. The methodology introduced here can be generally applied to survey the complex energy landscape in strongly correlated electron systems, avoiding the difficulty of electrostatic gating or confounding effects due to defects and/or disorder. In particular, the observation of robust non-thermal switching at meso-scales and at ultrafast timescales, provides a platform for designing high-speed low-energy consumption nano-photonics and electronics devices.