ASIAA/CCMS/IAMS/LeCosPA/NTU-Phys/NTNU-Phys Joint Colloquia

Sep 15, 2020

Shangjr (Felix) Gwo, Research Center for Applied Sciences, Academia Sinica

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 104, CCMS-New Phys. building
Title:
   Topological Photonics Based on Non-Hermitian Quantum Mechanics

Abstract

In conventional quantum mechanics, all physical observables can be obtained by Hermitian (self-adjoint) operators that acts on wave functions in Hilbert space and returns only real values. This is a reasonable assumption for closed quantum systems demanding energy and probability conservation. As a consequence, the Hamiltonian operator, which gives the total energy of the system, is equal to its transpose conjugate. By contrast, both gain and loss should to be considered in open quantum systems and the resulting non-Hermitian operator allows complex eigenvalues with the negative (positive) imaginary part corresponding to loss (gain) owing to coupling to the external environment.
Recently, non-Hermitian photonics based on PT-symmetry in open quantum systems has emerged as a powerful approach for topology-protected optical transport and novel photonic device applications, such as lasing and sensing. At present, most of non-Hermitian photonic systems employ the concept of PT-symmetry by precisely balancing gain and loss in coupled optical systems of diffraction-limited dielectric waveguides or microcavities, which can exchange energy spatially or temporally. In this talk, I will present some recent results from my group in the field of two-dimensional material non-Hermitian photonics adopting a new scalable and integrated experimental approach.

Brief Bio

Prof. Shangjr (Felix) Gwo received his Ph.D. in physics from the University of Texas at Austin, USA in 1993. From 1994 to 1997, he worked in Tsukaba, Japan as a researcher. He joined National Tsing-Hua University (NTHU), Hsinchu, Taiwan as a faculty member in 1997. From 2010 to 2014, he served as the Vice President for Research and Development in NTHU and he has been appointed as a Chair Professor of Physics since 2010.
From 2014 to 2018, Prof. Gwo served as the Director of National Synchrotron Radiation Research Center (NSRRC) in Hsinchu Science Park, Taiwan. NSRRC has two synchrotron light sources, including 1.5 GeV Taiwan Light Source (TLS) and 3.0 GeV Taiwan Photon Source (TPS). Starting from February 1st 2019, Prof. Gwo has been elected to serve as the Director of Research Center for applied Sciences (RCAS) in Academia Sinica, Nankang, Taipei, Taiwan.
Prof. Gwo’s research interests include semiconductor material physics, nanophotonics, plasmonics, and surface/interface science. Most recently, his research group works extensively on linear and nonlinear plasmonic metasurfaces, two-dimensional materials, plasmonic nanolasers, surface-enhanced Raman spectroscopy, and nitride nanostructure-based light-emitting devices. Prof. Gwo is an elected fellow of the American Physical Society (APS) and is also awarded The 23th National Chair Professorship (Ministry of Education) in 2020.

Sep 22, 2020

 George Wei-Shu Hou,  NTU-Physics

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Decadal Mission for the New Higgs/Flavor Era

Abstract

Why is “\(e\)”real? What gives electron mass? Who ordered the muon? Where have all the primordial antibaryons gone?
Starting from these questions, we introduce, in a heuristic way, the elements of modern particle physics: mass generation via gauge or Yukawa (complex) couplings to the Higgs sector, with scale set by spontaneous symmetry breaking. The muon question, however, grew into the Flavor problem: 3 copies of charge −1, −1/3 and +2/3 fermions, spanning a mass (Yukawa coupling) range of six orders of magnitude! With the landmark 2012 discovery of the \(h(125)\) boson completing a Higgs doublet, Gell-Mann’s “Totalitarian Principle” demands a second Higgs doublet must exist, and new \(H\), \(A\) and \(H^{+}\) bosons are likely below TeV scale, ideal for the Large Hadron Collider (LHC). They bring in a second set of Yukawa couplings that can effect baryogenesis and evade the electron electric dipole moment (\(d_{e} < 1.1 \times 10^{−29} \text{ } e \cdot \)cm), and can be probed by searches such as \(\mu \to e \gamma\) and \(\mu \to e\) conversion, and rare \(B\) meson decays. The Decadal Mission is to discover the extra Higgs bosons at the LHC, and to unravel Nature’s Design on Flavor (a new “periodic table”?). NTU would pursue both fronts.

Brief Bio

Prof. George Wei-Shu Hou holds an NTU Chair in the Physics Department since 2015. Receiving his Ph.D. at UCLA, he returned to NTU in 1992, after conducting theoretical research in Pittsburgh, Munich and PSI, Switzerland. He then initiated the NTU High Energy Physics experimental group. Recent significant honors are: Academic Award (2010, MOE), Academic Summit Project (2010-2015, NSC/MOST), National Chair (2012-2015, MOE). He became an APS Fellow in 2019.

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Sep 29, 2020

 Juhn-Jong Lin ,  NCTU-Electrophysics

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Oxygen Vacancy-Driven Orbital Multichannel Kondo Effect in Dirac Nodal Line Metals IrO\(_{2}\) and RuO\(_{2}\)

Abstract

Strong electron correlations have long been recognized as driving the emergence of novel phases of matter. A well-recognized example is high-temperature superconductivity which cannot be understood in terms of the standard weak-coupling theory. The exotic properties that accompany the formation of the two-channel Kondo (2CK) effect including the emergence of an unconventional metallic state in the low-energy limit also originate from strong electron interactions. Despite its paradigmatic role for the formation of non-standard metal behavior, the stringent conditions required for its emergence have made the observation of the nonmagnetic, orbital 2CK effect in real quantum materials difficult, if not impossible. We report the observation of orbital one- and two-channel Kondo physics in the symmetry- enforced Dirac nodal line (DNL) metals IrO\(_{2}\) and RuO\(_{2}\) nanowires and show that the symmetries that enforce the existence of DNLs also promote the formation of nonmagnetic Kondo correlations. Rutile oxide nanostructures thus form a versatile quantum matter platform to engineer and explore intrinsic, interacting topological states of matter [1] .

Reference: [1] S. S. Yeh, T. K. Su, A. S. Lien, F. Zamani, J. Kroha, C. C. Liao, S. Kirchner, and J. J. Lin, Nature Communications 11, 4749 (2020).

Brief Bio

Professor Juhn-Jong Lin (林志忠) received his BS degree in Electrophysics from National Chiao Tung University (Taiwan) in 1979, and PhD degree in Physics from Purdue University (USA) in 1986. He was a postdoctoral research fellow at University of Michigan–Ann Arbor (1986–1987) and University of Virginia at Charlottesville (1987–1988). He joined the Department of Physics at National Taiwan University as an Associate Professor in 1988, and became a full professor in 1992. He has been associated with the Institute of Physics and Department of Electrophysics at National Chiao Tung University since 1997. Professor Lin’s research interest focuses on experimental low- temperature condensed matter physics. He has studied quantum electron transport and dephasing, mesoscopic physics, Kondo physics, quantum phase transition, and dynamic defects in solids.

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Oct 06, 2020

 Chih-Wei Luo,  NCTU-Electrophysics

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Introduction to Ultrafast Science and Technology

Abstract

In this talk, I will introduce the development of ultrafast science and technology. Generally, the ultrashort laser pulses provide the high peak power and high time-resolution for the applications in various fields. For example, the high peak power can be used to fabricate the ZnSe and Se nanoparticles on the surface of an undoped (100) cubic ZnSe and Bi\(_{2}\)Se\(_{3}\) single crystals, respectively. Moreover, the nanostructures can be also induced on ITO films by femtosecond laser, which further enhance the conductivity and significantly reduce the transmittance in the blue-light region for eye protection. On the other hand, the study of ultrafast dynamics can be carried out in femtosecond time scale, e.g., snapshot the Dirac Fermions in topological insulators and study the exotic properties of topological surface states by pump-probe and THz emission spectroscopies. These results provide not only new insights in the optical coupling of topological surface states but also open up new opportunities for applying time-resolved spectroscopic characterization to solid state physics.

Brief Bio

Chih-Wei Luo is a Professor and a Vice Chairman in the Department of Electrophysics, National Chiao Tung University (NCTU), TAIWAN. After receiving his Ph.D. degree at NCTU, he joined NCTU in 2006 and started independent research. His current research interests include ultrafast dynamics in strongly correlated materials and photovoltaic materials, THz spectroscopy, and material processing by femtosecond lasers. His honors and awards include: Distinguished Young Investigator Grant of Ministry of Science and Technology (2014 & 2017); Young Scholar Outstanding Research Award in College of Science of National Chiao Tung University (2012).

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Oct 13, 2020

 Meng-Ru Wu ,  IoP AS

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Finding the Origin of Heavy Elements and Exploring the Nature of Dense Matter

Abstract

Astronomical and cosmological observations have been playing increasingly important roles in contributing to our understanding of fundamental properties and questions of physics in recent decades. In particular, the recent surge of multi- messenger astronomy brought hopes to solve a few long-lasting puzzles, e.g., the origin of heavy elements, the nature of dense matter, etc, with signals from the most catastrophic events in the universe: the explosive death of massive stars and the merger of two neutron stars. In this talk, I will introduce the background and recent progress made in pursuing these goals. I will also discuss some of the challenges and opportunities lying ahead, as well as our recent theoretical efforts with collaborators that can hopefully help shed light on yet-resolved issues with future observation.

Brief Bio

Meng-Ru Wu received his PhD degree from the University of Minnesota, USA in 2012. He was a postdoctoral fellow in the Technische Universität Darmstadt, Germany from 2013 to 2016 and in the Niels Bohr Institute, Denmark during 2016-2017. He joined the Institute of Physics, Academia Sinica as an Assistant Research Fellow in late 2017 and is currently a joint fellow in the Institute of Astronomy and Astrophysics, Academia Sinica as well as a Junior Scientist in the Physics Division of the National Center for Theoretical Science. His research interests span a wide range in the fields of nuclear astrophysics and particle astrophysics, with particular focus on the nucleosynthesis of heavy elements, neutrino flavor conversions in dense media, and probing physics beyond the Standard Model with astrophysics.

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Oct 20, 2020

 You-Hua Chu ,  ASIAA

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   CSI: Type Ia Supernova Remnant in Taiwan

Abstract

Searching for clues on supernovae (SNe) from their supernova remnants (SNRs) is like a crime scene investigation (CSI). This talk is based on Type Ia SNR work by my students and postdoc in Taiwan. Type Ia SNe have been used as standardizable candles to discover the accelerated expansion of the Universe; however, we still are not certain how Type Ia SNe exploded exactly. Two popular scenarios have been suggested, one involves a white dwarf (WD) having accreted too much material from a normal-star companion, and the other involves merger of two WDs. In the former scenario, the stellar companion survives the SN explosion, while in the latter scenario no stellar remnant is left. We have been studying the Type Ia SNRs in our neighboring galaxy the Large Magellanic Cloud (LMC), using Hubble Space Telescope images to search for surviving companions of their SN progenitors and dense circumstellar material ejected by the SN progenitors. I will report our findings and suggest possible explosion mechanisms. I will also report on our search for young Type Ia SNRs in the M33 galaxy. The goal of this research is to understand the explosion mechanisms of Type Ia SNe.

Brief Bio

You-Hua Chu graduated from NTU Physics in 1975 and obtained her Ph.D. in Astronomy from UC Berkeley in 1981. She was a postdoc at Univ. of Wisconsin- Madison and a Lindheimer Fellow at Northwestern Univ. She went to Univ. of Illinois at Urbana-Champaign in 1985, and became Full Professor in 1997 and served as the Chair of Astronomy Dept in 2005-2011. She returned to Taiwan to work at Academia Sinica Institute of Astronomy and Astrophysics as Director (2014-2020) and Distinguished Research Fellow (2014-pres). She was the President of the Astronomical Society of the Republic of China (2014-2020). Her main research fields include Interstellar and circumstellar medium, star formation and feedback, Magellanic Clouds, dust disks around white dwarfs. She is a member of American Astronomical Society (AAS) and International Astronomical Union (IAU), and was President of Division VI (Interstellar Matter) of IAU in 2009-2012. She has served on numerous review and award committees for NASA, NSF, AAS, and AURA. She received the Outstanding Alumni Award from NTU Physics in 2016. She has published over 250 refereed journal papers and over 100 conference proceeding papers.

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Oct 27, 2020

 Yeukuang Hwu ,  IoP AS

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Whole Brain Mapping with X-rays

Nov 03, 2020

 Chung-Hou Chung ,
      NCTU-Electrophysics
      NCTS-Physics

Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Uncover the mystery of strange metal state in correlated electron systems

Abstract

Over the recent decades, there has been growing experimental evidences in correlated electron systems of which thermodynamic and transport properties violate the Landau’s Fermi liquid paradigm for metals. These non- Fermi liquid behaviors, ranging from unconventional superconductors, heavy-fermion metals and superconductors, magic-angle twisted bi-layered graphene, to Kondo quantum dots, often exist close to a magnetic quantum phase transition and exhibit so-called “strange metal (SM)” phenomena: with (quasi-)linear-in-temperature resistivity and singular logarithmic-in-temperature specific heat coefficient. In spite of the ubiquitous presence of SM features in experiments across a wide range of materials, the microscopic origin of them is largely un-explained, and it has become an outstanding open problem in correlated electron systems. In this talk, I first take an overview of the SM phenomena. I further offer a microscopic mechanism to uncover this mystery seen in quasi-two-dimensional heavy- fermion metals [1] and superconductors [2] . This mechanism is based on coexistence and competition between the Kondo correlation and the quasi-2d short-ranged antiferromagnetic resonating-valence-bond spin-liquid near the antiferromagnetic Kondo breakdown quantum critical point [3] [4] . The interplay of these two effects via critical spin and charge fluctuations provides an excellent account for the SM phenomena. The extension of this theory [5] to the newly discovered strange metal “phase” (ground state) in a class of paramagnetic frustrated Kondo lattice materials [6] is discussed.


Reference:
[1] J. Custers et al., Nature 424, 524 (2003); J. Custers et al., Phys. Rev. Lett. 104, 186402 (2010).
[2] C. Petrovic et al., J. Phys. Condens. Matt. 13, L337 (2001); R. Movshovich et al. Phys. Rev. Lett.86, 5152 (2001); S. Zaum et al. Phys. Rev. Lett. 106, 087003 (2011).
[3] Yung-Yeh Chang, Silke Paschen, Chung-Hou Chung, Phys. Rev. B 97, 035156 (2018).
[4] Y.Y. Chang et al., Phys. Rev. B 99, 094513 (2019).
[5] Jiangfan Wang, Yung-Yeh Chang, and Chung-Hou Chung, arXiv: 2005.03427.
[6] H. Zhao et al., Nat. Phys. 15, 1261 (2019).


Brief Bio

Chung-Hou Chung is a professor in Department of Electrophysics, National Chiao-Tung University, HsinChu, Taiwan. He received his PhD from Brown University, USA in 2002. He was a postdoctoral research associate at University of Toronto (2002-2004) and Karlsruhe Institute of Technology (KIT) (2004-2006), Germany before he joined the faculty at National Chiao-Tung University in 2006. His research interest is theoretical condensed matter physics with special focuses on quantum phase transitions and quantum critical phenomena in strongly correlated electron systems. He was a visiting scholar at Yale University, Rutgers University, Brookhaven National Laboratory, Kavli Institute of Theoretical Physics (KITP) at UCSB, the Max-Planck Institute for Complex Systems, Dresden, and International Center for Theoretical Physics (ICTP), Italy. His most well-known and highly cited works include: 1. Prediction of an exotic valance-bond-solid phase of the frustrated anti-ferromagnet on two-dimensional Shastry- Sutherland lattice together with J.B. Marston and S. Sachdev in 2001, which was later realized experimentally in 2017. This work was highlighted by S. Sachdev in his Onsarger Prize talk in 2018; 2. Theory of quantum criticality in a double quantum dot system. It motivates extensive further theoretical and experimental studies; 3. Theory on non- equilibrium transport at a dissipative quantum phase transition, a pioneer work on a new research field: quantum phase transition out of equilibrium. His research works were recognized both internationally via various invited talks in international conferences and in Taiwan by Outstanding Young Researcher Grant of NSC and the Center Scientist of the National Center for Theoretical Sciences (NCTS).

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Nov 10, 2020

 Wen-Hao Chang ,  NCTU-Electrophysics
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   2D Semiconductors: Opportunities and Challenges

Abstract

Recent advances in semiconducting 2D materials, such as transition metal dichalcogenide (TMD) monolayers, have opened up new opportunity in electronic devices for tackling the bottleneck of device scaling. However, for practical industrial applications, a bundle of challenges remains, such as growing high-quality and large-area (wafer scale) materials, exploring new materials with better carrier mobility and developing scalable fabrication method to reduce the contact resistance. On the other hand, stacking different 2D materials into van der Waals (vdW) heterostructures can create new quantum materials with fascinating properties that do not exist in natural materials, further providing new opportunity for novel device applications. In this talk, I will present our recent endeavors on the material synthesis, fundamental physics study and device applications of 2D TMDs. I shall demonstrate the growth of various TMD monolayers by chemical vapor deposition (CVD), particularly on metallic surface. Transistors based on 2D TMDs will also be demonstrated. The unique properties of valley-spin coupled physics in monolayer TMD, and the manipulation of light-matter coupling using photonic and plasmonic structures will be introduced and discussed. I will also show new excitonic properties endowed by the moiré structure in twisted heterobilayers.

Reference:
[1] J. Choi et al., Science Adv. 6, eaba8866 (2020).
[2] L.-S. Lu et al., ACS Nano 14, 4963 (2020).
[3] T.-A. Chen et al., Nature 579, 219 (2020).
[4] W.-T Hsu, Science Advances 5, eaax7407 (2019).
[5] W.-T. Hsu et al., Nature Comm. 9, 1356 (2018).
[6] W.-T. Hsu et al., Nature Comm. 8, 929 (2017).
[6] W.-T. Hsu et al., Nature Comm. 6, 8963 (2015).
[6] M.-Y. Li et al., Science 349, 524-528 (2015).


Brief Bio

Dr. Chang is currently a distinguished professor of physics at National Chiao Tung University (NCTU), Taiwan. He received his BS (‘94), MS (‘96) and PhD (‘01) degrees in Physics from National Central University (NCU), Taiwan. After his postdoctoral research at NCU, he joined the Department of Electrophysics at NCTU as an assistant professor in 2005 and became a full professor since 2012. His research interests include light-matter interactions in semiconductor nanostructures, nanophotonics/ plasmonics hybrid systems, and 2D layered materials. He has authored and co-authored more than 100 journal papers and received citation more than 6,800 times with an h index of 37, according to Google Scholar. He was awarded the Distinguished Teaching Award (2010, 2016) from NCTU, the Ta-Yu Wu Memorial Award (2010) and the Distinguished Research Award (2018) from the Ministry of Science and Technology (MOST) of Taiwan, the Academic Award (2018) from the Sun Yat-Sen Academic and Cultural Foundation, and the Achievement in Asia Award (Robert T. Poe Prize, 2020) given by the International Organization of Chinese Physicists and Astronomers (OCPA). Dr. Chang served as the Convener of Physics Division in MOST during 2016-2018 and is currently the Editor of Chinese Journal of Physics, the Editorial Board Members of Scientific Report and the Editorial Advisory Board of Applied Physics Letters.

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Nov 17, 2020

 Feng-Chuan Chuang ,  NSYSU-Physics
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Topological Phase and Band Engineering of 2D Materials

Abstract

Ultrathin two-dimensional (2D) materials have recently attracted intense interest. I will discuss some aspects of these advanced 2D materials. 2D topological insulators (TIs), also known as quantum spin Hall (QSH) insulators, are recently discovered novel materials in which, even though the bulk material is insulating, the system still supports spin-polarized, gapless edge states with Dirac-cone-like linear energy dispersion. Growing substrate-supported 2D topological insulators which can be integrated into the modern silicon industry is highly desired for spintronics. My group has predicted and proposed several 2D topological insulators using first-principles electronic structure calculations for materials realization. Band engineering of honeycomb like materials and 2D transition metal dichalcogenides (TMDs) is of importance for tuning and possible enhancement of their electronic, physical and topological properties toward industrial applications. These findings suggest new opportunities for the scientists in the field of surface physics.

Brief Bio

Prof. Feng-Chuan Chuang graduated from National Taiwan Normal University with a B.S. in Physics in 1997. He obtained his M.S. and Ph.D. in Condensed Matter Physics at Iowa State University in 2003 and 2005, respectively.
Starting Feb. 2006, he began his career at the National Sun Yat-Sen University as an Assistant Professor. Prof. Chuang was given the National Sun Yat-sen University Young Scholar Award in 2010. He was promoted to associate and full professor in 2009 and 2013, respectively. He served as the chairman of Physics department from 2014/8~2016/7, and hosted the 2016 annual meeting of Physical Society of Taiwan. Prof. Chuang was again given the National Sun Yat-sen University Outstanding Research Award in 2016. He received the Excellent Young Scholar Research Grant of MOST in 2018.
His research interests include condensed matter physics, computational materials physics, materials design, surface science, first-principles calculation, molecular dynamics, and genetic algorithm, to name a few. He has published works on atomic clusters, semiconductor and metal surfaces, topological insulators, and advanced 2D materials. He has developed the structural optimization and materials design algorithms for predicting and studying quantum materials. He has predicted and engineered numerous two dimensional topological materials which harbors quantum spin Hall effect and quantum anomalous Hall effect. He has collaborated closely with experimental groups to study electronic properties of advanced 2D materials and surface physics. Overall, he has published numerous papers in some of the most prestigious journals, such as Physical Review Letters, Nano Letters, Science Advances, Nature Communications, Small, and ACS Nano.

Nov 24, 2020

 Chin-Fei Lee ,  ASIAA
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Unveiling The Early Processes of Star Formation With ALMA

Abstract

Stars like our Sun are forming everywhere in our home galaxy, the Milky Way. ALMA stands for Atacama Large Millimeter/Submillimeter Array and is currently the largest radio interferometry array on Earth. With its unprecedented sensitivity and resolution, we have mapped a few young star-forming regions in great detail, making a few breakthrough discoveries in the study of star formation. In this talk, I will first briefly introduce the current theory of star and planet formation with some ALMA results. Then, I will present our ALMA results of star formation in detail. In particular, I will report our results of accretion disks and jets around the forming stars and discuss their formation mechanisms. The accretion disks are expected to evolve later into protoplanetary disks in which planets are formed. I will also report the detection of more than 10 organic molecules including prebiotic molecules in one of the accretion disks. These molecules could be passed down to protoplanetary disks and thus incorporated into the planets to be formed later.

Brief Bio

Chin-Fei Lee obtained his PhD degree in Astronomy from the University of Maryland, USA in 2001. He was a postdoctoral fellow in the NASA/JPL/Caltech, USA from 2001 to 2003, and in the Harvard-Smithsonian Center for Astrophysics – Submillimeter Array Project, USA from 2003-2006. He joined the Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA) as an Assistant Research Fellow in late 2006, and is currently a Research Fellow and an Acting Deputy Director. He is also a joint Professor in the Physics Department of National Taiwan University. He also serves as the PI of ALMA-Taiwan project and manages an ASIAA CASA Development Center (ACDC) for ALMA softwares. He is also a member of International Astronomical Union (IAU). He mainly studies the formation and evolution of Sunlike stars, and aims to uncover their physical processes with radio observations and magneto-hydrodynamical simulations.

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Dec 01, 2020

 Chi-Jen David Lin,  NCTU-Physics
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Lattice Field Theory and Physics Beyond the Standard Model

Abstract

Searching for physics beyond the standard model (BSM) is arguably one of the most important issues in particle physics. It involves experimental, phenomenological, as well as field-theoretical studies. In this talk, I will deliver an introduction to recent progress in lattice field theory (LFT) relevant to the last of the above three ingredients. It will be explained that non-perturbative aspects of quantum field theory can play an important role in this avenue of research. The Higgs-Yukawa theory and composite Higgs models are employed as illustrations. In return, inspired by these studies, advances in LFT have been made. As an example, I will briefly discuss the tensor-network formulation for lattice field theory, which can be used to gain further insights for such investigations in the future.

Brief Bio

Chi-Jen David Lin is currently a professor at Institute of Physics, National Chiao-Tung University (NCTU). He graduated from National Taiwan University in 1993, and obtained his PhD degree from the University of Edinburgh in January 1999. He then held postdoctoral research associate positions at the University of Kentucky in Lexington (January - September 1999), the University of Southampton (October 1999 - August 2003) and the University of Washington in Seattle (September 2003 - August 2006). After a short-term visitorship at the University of Cambridge (October 2006 - January 2007), he joined the faculty at NCTU in February 2007. David Lin's main research interest is lattice field theory. Over the past two decades he contributed to various aspects of this subject. These include topics related to composite Higgs models, the tensor-network formulation, as well as QCD matrix elements in flavour physics and hadron structure. In addition to his research, David Lin has also been actively participating in synergetic efforts in the community. He has been regularly serving on the international advisory committee of the annual international symposium on lattice field theory in recent years, and he was a member of the Flavour Lattice Averaging Group from 2014 to 2019. Professor Lin was awarded an Outstanding Young Investigator grant from the Ministry of Science Technology for the period between August 2016 and July 2020.

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Dec 08, 2020

 Hung-Duen Yang ,  NSYSU-Physics
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Discovery of Room-temperature Superconductor: a Race to Nobel Prize

Abstract

Recent discovery of room-temperature superconductivity with \(T_c\) ~ 287 K in C-S-H composite under high pressure ~ 267 GPa has been attracted much attention. The question quickly arises: Will they get Nobel Prize soon? In this presentation, I will first introduce the three unique phenomena of superconductivity. Then I will give some exotic superconductors with the mechanism beyond BCS theory before 1986. The scrambling story of searching higher-\(T_c\) superconductors, such as Cu- and Fe-containing oxides, KC\(_{60}\), and MgB\(_{2}\) after 1986 will be shown with its amazing citations. Further progress on high-pressure induced high-\(T_c\) superconductivity in metal-hydrides will be timely presented. Final question: who are going to win the race and possibly catch the Crown of Nobel Prize? The answer is left to audiences.

Brief Bio

Professor Hung-Duen Yang received BS physics from NTNU in 1978 and completed his Ph.D. physics from Iowa State University in 1987. He has worked as the Professor and the Chairman in Physics, the Chairman of Physics, Dean of College Science and President in National Sun Yat-Sen University since 1987. During the period of 2001~2016, he also intermittently served short-term administrative positions of the Director General of Natural Sciences and Deputy Chairman in NSC and the Minister of MOST. Professor Yang’s academic research is mainly focusing on the low-temperature condensed-matter experimental physics, in particular specific-heat and high-pressure studies on superconductivity and magnetism.

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Dec 15, 2020

 Shin-Shan Yu ,  NCU-Physics
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Search for Dark Matter in pp Collisions with CMS

Abstract

Astrophysical observations have provided strong evidence for the existence of dark matter in the universe. However, its underlying nature remains unknown and cannot be accommodated within the standard model. A search for dark matter at the larger hadron collider allows us to probe a wide range of dark matter-normal matter interactions. In this talk, I will give a brief overview of dark matter, an introduction to the large hadron collider and the CMS detector. I will also present the results of the searches for dark matter, using the proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS detector.

Brief Bio

Prof. Shin-Shan Yu received her Ph.D. from the University of Pennsylvania in 2005 and worked as a research associate at the Fermi National Accelerator Laboratory from 2005 to 2009. During her years at the US, She was an active member of the Collider Detector at Fermilab (CDF) Collaboration and contributed significantly to the commissioning of the central outer tracker, the development of photon background estimation, and the physics with b-baryons and photons. In August 2009, she returned to Taiwan and joined the faculty of the Department of Physics, National Central University (NCU). She also moved her focus from the experiment at the US to the experiment at Europe, the Compact Muon Solenoid Experiment (CMS) at the Large Hadron Collider (LHC). At CMS, she has worked on QCD photon physics and searches for new physics with the Higgs boson. Her current research at CMS focuses on the search for dark matter. Starting from 2020, she is also involved in the development of a haloscope to search for axions at Taiwan.

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Dec 22, 2020

 Miranda Chih-Ning Cheng,  IoP, University of Amsterdam
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   The Romance between Physics and Mathematics

Abstract

In this colloquium I will first recall the general history of the interaction between mathematics and physics. Subsequently, I will describe the sub- field of string math, focussing on the topics of moonshine and "stringy" topological invariants. Finally, I will end with some musings on the future of the relationship between physics and mathematics.

Brief Bio

I graduated from NTU Physics in 2001, obtained Master degree in theoretical physics from the Utrecht University, the Netherlands under the supervision of the Nobel laureate Gerard 't Hooft, and then obtained my PhD degree with Prof. Erik Verlinde in theoretical physics from the University of Amsterdam in 2008. After that I did four years of postdocs in Harvard University, first in the physics and then in the mathematics department. I returned to Europe in 2012 as a mathematician in Sorbonne Université in Paris. Since 2014, I have been back in the University of Amsterdam as an associate professor in both the physics as well as the mathematics department. My research interests lie on the boundary of physics and mathematics, and occasionally also machine learning.

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Dec 29, 2020

 Ying-Hao Eddie Chu,  Department of Materials Science & Engineering, NCTU
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   MICAtronics: A New Platform for Soft Transparent Technology

Abstract

A new world is being formed based on the technologies composed of artificial intelligence, Internet of Things (IoT), and robots. Especially, in the research fields of IoT and robotics systems, a device with mechanical flexibility can deliver more degrees of freedom as far as the design aspects are concerned. Therefore, the development of soft and flexible electronics becomes an important research direction for wearable and IoT devices. Due to the mechanical flexibility, polymer materials and thin metal foils are commonly used in the fabrication of flexible electronic systems. However, the reliability issue under practical operations hinders the applications of these flexible electronics, especially for those on polymer based substrates. This is attributed to a mismatch of thermal expansion coefficient between substrate and functional materials or low thermal and chemical endurance of polymers and organic materials. A lot of researchers are working hard and together to expand the applicability of current flexible devices. However, new pathway to flexible electronics can also be developed in parallel to provide more subtle solutions, thus in need of new platform to integrate functional materials with good thermal and chemical stabilities together with mechanical flexibility. In this research field, oxides can play an important role due to their intriguing functionalities and superior thermal and chemical stabilities. To deliver high-quality thin films or structures based on oxides, heteroepitaxy is essential. However, the lack of a suitable approach remains an obstacle for flexible oxide heteroepitaxy. van der Waals epitaxy (vdWE) involving two-dimensional layered materials can play a crucial role in the expansion of thin film epitaxy by overcoming the bottleneck of material combinations due to lattice/thermal matching conditions inherent to conventional epitaxy. In this study, we use a 2D material as the substrate. In this talk, we confine ourselves to the validity of vdWE of functional oxides on muscovite mica throughout this treatise. With such demonstrations, it is anticipated that MICAtronics, vdWE on mica, can reveal unusual properties and emergent phenomena in the realm of high-performance flexible device applications.

Brief Bio

Professor Chu received his PhD from the Department of Materials Science & Engineering in National Tsing-Hua University in 2004. Then, he joined University of California, Berkeley as a postdoc. In 2008, he acquired an assistant professorship in the Department of Materials Science & Engineering at National Chiao Tung University. He was promoted to an associate professor in 2015, and then he was promoted to a professor in 2018. From 2019, he was appointed as a distinguished professor. Since 2013, he has an adjunct position in institute of physics, Academia Sinica. In 2014 he started an adjunct position in the Department of Electrophysics, National Chiao Tung University. From 2016 to 2018, he had the adjunct position in the Material and Chemical Research Laboratories, Industrial Technology Research Institute and the International College of Semiconductor Technology at National Chiao Tung university. From 2019, he has an appointment with ACS Applied Electronic Materials to be an associate editor. His research is highly focused on complex functional oxides and strongly correlated electron systems. He has extensive experience in the use of advanced characterization techniques to understand and manipulate functional oxide heterostructures, nanostructures, and interfaces. His current goal is to create a pathway to use high quality oxide heteroepitaxy for soft transparent technology. Now, he is a pioneer with the most publication along this research direction. He has published >300 papers (Web of Science: ~20000 citations, h-index=65; Google Scholar: >25000 citations, h-index=74) in academic journals, including Science series (3), Nature series (~25), PNAS (2), ACS Nano & Nano Letters (>25), Advanced (Energy or Functional) Materials (>20), Nano Energy (>5), Physical Review series (>25), Applied Physics Letters (~40).

Slides
Video

Jan 05, 2021

 ChiiDong Chen,  IoP AS
Host:  Pao-Ti Chang
Time: 2:20 pm -3:20 pm
Place: Room 204, CCMS-New Phys. building
Title:
   Superconducting qubits – Design, Fabrication and Measurement

Abstract

Quantum computer is a new generation of quantum technology, and qubit is the building component of quantum computers. There are several manifestations of qubits, among them superconducting qubit is one of the relative mature forms. In this talk, I will talk about our research work on superconducting qubits, including the considerations of chip design, manufacturing method, and circuits for controlling and measuring qubits. Finally, I will also describe our two-bit design and measurement scheme.

Brief Bio

ChiiDong Chen received his PhD degree from the Department of Physics at Chalmers University of Technology, Sweden, where he studied Superconductor-Insulator Phase Transitions in 2D arrays of small Josephson junctions. After graduated, he moved to NEC fundamental research laboratories, Tsukuba, Japan serving as a postdoc, there he studied Cooper- pair tunneling in Superconducting Single-Electron-Transistors. In 1997, he joined the Institute of Physics, Academia Sinica as a faculty member. His research interests span a broad range in the fields of superconducting devices as well as mesoscopic devices comprising 2D materials. His recent research topic is on the superconducting qubits.

Video