September 11, 2017
Kang L. Wang , UCLA
Host: Yuan-Huei Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Quantized Signature of Majorana Fermion: Particle being its own Anti-particle
In 1937, Ettore Majorana proposed a particle being its antiparticle. Since its inception, Majorana has been under intensive pursuit both theoretically and in experiments. Recent interest in robust topologically protected quantum computing has accelerated the experimental quest of Majorana. Among various proposals, I will discuss the scenario when a topological insulator meets a superconductor. This system offers a possible host for Majorana.
The talk will begin from the experimental efforts of the quest of dissipationless transport: quantum Hall without magnetic field, quantum spin Hall to quantum anomalous Hall (QAH). The latter was enabled by a long term effort in the materials growth of topological insulator - magnetic (Cr) doped BiSbTe to achieve reliably QAH. The recent work of topological insulator (TI) has led to the recognition of the importance of topology phase in condensed matters by the 2016 Nobel Prize in Physics. I will discuss the topological transitions of Dirac electrons for TI in QAH. When the QAH edge states interface with a superconductor, the Dirac electron space is transformed to the Nambu space, hosting Majorana fermions via pairing energy. We will describe our experimental efforts to show the convincing evidence of quantized signature of the one-dimensional chiral Majorana fermion . A half-integer quantized conductance plateau (0.5 e2/h) gives a firm signature of the elusive Majorana fermion for the first time by scanning topological phase transitions under the reversal of the magnetization. This finding gives a new direction for new topological quantum computing.
Reference. Science, July 21, 2017
Dr. Kang L. Wang is currently Distinguished Professor and the Raytheon Chair Professor in Physical Science and Electronics in the University of California, Los Angeles (UCLA). He is affiliated with the Departments of ECE, MSE and Physics. He received his BS degree from National Cheng Kung University (Taiwan) and his MS and PhD degrees from the Massachusetts Institute of Technology. He is a Member of Academia Sinica, Fellow of the IEEE, and a member of the American Physical Society. He was a Guggenheim Fellow. He also served as Editor-in-Chief of IEEE TNANO, editor of Artech House, Consulting Editor for Spins, and Associate Editor for Science Advances. His research areas include nanoscale physics and materials; topological insulators; molecular beam epitaxy; spintronics and low dissipation devices; neurodynamics and neurotronics.
The functionalities of traditional optical component are mainly based on the phase accumulation through the propagation length, leading to a bulky optical component such as lens and waveplate. Plasmonic metasurfaces composed of artificial structures have attracted a huge number of interests due to their ability on controlling the optical properties including electromagnetic phase as well as amplitude at a subwavelength scale . They therefore pave a promising way for the development of flat optical devices and integrated optoelectronic systems. In this talk, several research topics for photonic applications based on metasurfaces will be performed and discussed: Beam deflection , highly dimensional holographic imaging , versatile polarization generation and analysis , multi-functional and tunable metadevices , achromatic metasurface devices  and engineering non-radiating anapole mode in free space .
 N. Yu, and F. Capasso, Nat. Mater. 13, 139-150 (2014).
 S. Sun, et. al., Nano Lett. 12, 6223-6229 (2012).
 Y.-W. Huang, et. al., Nano Lett. 15, 3122-3127 (2015).
 P. C. Wu, et. al., Nano Lett. 17, 445-452 (2017).
 Y.-W. Huang, et. al., Nano Lett. 16, 5319-5325 (2016).
 S. M. Wang, P. C. Wu, et. al., Nature Commun. 8, 187 (2017).
 P. C. Wu, et. al., under review.
Din Ping Tsai received Ph.D in Physics from University of Cincinnati, USA in 1990. He worked at Micro Lithography Inc., California, USA; Ontario Laser and Lightwave Research Center, Toronto, Canada; and National Chung Cheng University, Taiwan from 1990 to 1999. He joined Department of Physics, National Taiwan University as an Associate Professor in 1999, and became Professor and Distinguished Professor in 2001 and 2006, respectively.
He served as the Director General of the Instrument Technology Research Center (NARL) located in Hsinchu Science Park, Taiwan from 2008 to 2012. He is the Director and Distinguished Research Fellow of Research Center for Applied Sciences, Academia Sinica since 2012. He is a Fellow of AAAS, APS, IEEE, OSA, SPIE, TPS and Electro Magnetics Academy. He is also Academician of Asia Pacific Academy of Materials and Corresponding Member of International Academy of Engineering.
He currently serves as Editor of Progress in Quantum Electronics, Associate Editor of Journal of Lightwave Technology, Member of Editorial boards of Physical Review Applied, Optics Communications, Plasmonics, ACS photonics, and Optoelectronics Letters, respectively. He is now the President of Taiwan Information Storage Association. He was the Director of the Board of SPIE and Committee Member of IEEE/LEOS Nanophotonics; OSA Fellows & Honorary Members; SPIE Fellow; IEEE Joseph F. Keithley Award; OSA and IS&T Edwin H. Land Medal; respectively. He was also President of Taiwan Photonics Society; Chairman of IEEE Instrument and Measurement Society Taipei Chapter; and Chairman of the SPIE Taiwan chapter.
Ing-Shouh Hwang , IoP AS
Host: Ming-Wen Chu
Time: 2:20 pm -3:20 pm
Place: Room 104, CCMS-New Phys. building
Low-Voltage Coherent Electron Imaging
Based on a Single-Atom Electron Source
Imaging of two-dimensional materials and low-atomic-number materials has been one of the most intensively studied subjects in electron microscopy. It has been a general trend to develop low-voltage electron microscopes due to their high imaging contrast of the sample and low radiation damage. Atom-resolved TEM images with operation voltages as low as 15 to 40 kV have been demonstrated in recent years due to advancement in aberration correction techniques. However, such techniques become extremely challenging and complicated as the operating voltage reaches levels lower than 10 kV. Electron beams with energy from 500 eV to 10 keV have not been demonstrated to achieve atomic resolution. In this talk, I will discuss new schemes based on highly coherent single-atom electron sources.
Over the past several years, we have been developing low-voltage (805000 V) coherent electron imaging techniques. An advantage of this approach is that there is a possibility to achieve diffraction-limited resolution without the need to fabricate a high-quality lens. Coherent diffractive imaging has been successfully demonstrated in optical microscopy and x-ray microscopy. There are relatively fewer experiments in electron microscopy mainly because optical lasers and synchrotron light sources are usually with better coherence than electron sources. Now we have demonstrated full spatial coherence for single-atom electron sources. Thus coherent imaging based on single-atom electron sources is very promising to reach atomic resolution even for non-periodic structures like biological molecules. Our ultimate goal is to achieve high-contrast and high-spatial-resolution imaging of two-dimensional materials and organic molecules under low-dose conditions.
1993 Ph.D Applied Physics, Division of Applied Science, Harvard University
1984 B.S. Department of Electrical Engineering, National Taiwan University, Taiwan
2005 Adjunct Professor, Department of Material Sciences and Engineering, NTHU
2000 Research Fellow, Institute of Physics, Academia Sinica
2000 Adjunct Associate Professor, Department of Physics, NTHU
1998 Associate Research Fellow, Institute of Physics, Academia Sinica.
1994 Assistant Research Fellow, Institute of Physics, Academia Sinica
1993 Postdoctoral Fellow, Applied Physics, Harvard University
2006 Outstanding Nano-tech Research Award, Taiwan Nanotechnology Industry Development Association.
2000 Outstanding Research Award, National Science Council.
1999 Young Investigator Award, Academia Sinica.
surface and interface sciences, scanning probe microscopy, electron/ion beam techniques, development of new instrumentation techniques
Live Streaming and Video
Theoretical Nuclear Physics has entered a new era. Using the powerful machinery of chiral effective Lagrangians, the forces between two, three and four nucleons can now be calculated with unprecedented precision and with reliable uncertainties. Furthermore, Monte Carlo methods can be adopted to serve as a new and powerful approach to exactly solve nuclear structure and reactions. I discuss the foundations of these new methods and provide a variety of intriguing examples. Variations of the fundamental constants of Nature can also be investigated and the consequences for the element generation in the Big Bang and in stars are considered. This sheds new light on our anthropic view of the Universe.