Joint Colloquia

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

Coordinators:

Chia-Hung Chang (NTNU Phys), Ssu-Yen Huang (NTU Phys), Shao-Yu Chen (CCMS), Cheng-Tien Chiang (IAMS), Jiwoo Nam (LeCosPA), Tomomi Sunayama (ASIAA), Shang-Min Tsai (ASIAA)

Feb. 24, 2026 (week 01)

Ting-Wen Lan

Assistant Professor, National Taiwan University

Tracing Gas In and Around Galaxies

Host: Ssu-Yen Huang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Galaxies evolve by regulating the amount of gas in and around them. By observationally exploring the connections between gas and galaxies, we can better understand the physical mechanisms driving galaxy evolution. In this talk, I will present results from a series of studies focused on exploring and characterizing the properties of gas in and around galaxies. I will first introduce the Dark Energy Spectroscopic Instrument (DESI), which provides the largest spectroscopic dataset available for extracting gas properties through emission and absorption line features. I will then present three major research directions: (1) exploring the diversity of gas profiles within galaxies, (2) a comprehensive characterization of gas surrounding galaxies, and (3) the development of the DESI-II survey. I will show that by combining large multi-wavelength datasets with statistical and machine learning techniques, we can not only obtain observational measurements with unprecedented precision, but also uncover new astrophysical phenomena — offering deeper insight into the underlying physical processes at play.

Brief Bio

Ting-Wen Lan is an Assistant Professor in the Graduate Institute of Astrophysics and the Department of Physics at National Taiwan University. He is a Yushan Young Fellow awarded by the Ministry of Education and a joint Assistant Research Fellow at Academia Sinica Institute of Astronomy and Astrophysics. He received his PhD in astrophysics from Johns Hopkins University in 2016 and held independent postdoctoral research positions at the Kavli IPMU at the University of Tokyo and the University of California, Santa Cruz, before joining NTU in 2021. His research focuses on galaxy astrophysics, combining large observational datasets with statistical and machine learning techniques to uncover novel astrophysical signals.

Video

20260224.mp4

Mar. 3, 2026 (week 02)

Shau-Yu Lan

Associate Professor, National Taiwan University

Fast Quantum Gas Formation via Electromagnetically Induced Transparency Cooling

Host: Ssu-Yen Huang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Ultracold quantum gases play a pivotal role in many-body physics, quantum sensing, and quantum simulation. Over time, methods such as evaporative cooling in bulk ensembles and precision laser cooling techniques have been employed to achieve quantum degeneracy in atomic gases. The pursuit of a simpler, faster way to form quantum gases thus holds significant promise for advancing the field. In this talk, I will report on our creation of a quantum gas by cooling individual rubidium atoms pinned in a three-dimensional optical lattice using electromagnetically induced transparency and adiabatic expansion. After just 10 milliseconds of cooling, we verify the phase transition from a thermal to a quantum gas by adiabatically transferring the atoms into optical dipole traps. We observe the collapse of atoms in three-dimensional traps, a distinctive hallmark of a quantum gas with negative scattering length. Our results introduce a versatile and fast approach to achieving quantum degenerate gases with minimal time and resource requirements.

Brief Bio

Dr. Shau-Yu Lan earned his B.S. from National Tsing Hua University in 2002 and received his Ph.D. from Georgia Institute of Technology in 2009. He then conducted postdoctoral research at the University of California, Berkeley. In 2013, He joined Nanyang Technological University in Singapore as a National Research Foundation (NRF) Fellow and Nanyang Assistant Professor. In 2023, He transitioned to the Department of Physics at National Taiwan University.

Video

20260303.mp4

Mar. 10, 2026 (week 03)

Tien-Ming Chuang

Associate Research Fellow, Institute of Physics, Academia Sinica

Disorder Driven Electronic Smectic Phase and Charge Density Wave in a Nonsymmorphic Sb Square-net Semimetal

Host: Ssu-Yen Huang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Electronic liquid crystal (ELC) phases are spontaneous symmetry breaking states believed to arise from strong electron correlation in quantum materials such as cuprates and iron pnictides. Here, we report a direct observation of a smectic phase in a weakly correlated non-symmorphic Sb square-net semimetal, GdSbxTe2-x. Incommensurate smectic charge modulation and intense local unidirectional nanostructure, which coexist with Dirac fermions across Fermi level, are visualized by using spectroscopic imaging-scanning tunneling microscopy. As materials with highly mobile carriers are mostly weakly correlated, the discovery of such an ELC phase are anomalous and raise questions on the origin of their emergence. Specifically, we demonstrate how chemical substitution generates these symmetry breaking phases before the system undergoes a charge density wave (CDW)-orthorhombic structural transition [1]. Furthermore, the local unidirectional nanostructures appear coupled strongly with the CDW order. We will discuss the role of disorder in comparison with the recent claim of the bond density wave in CeSbTe [2]. Together, our results highlight the importance of impurities in realizing ELC phases and present a new material platform for exploring the interplay among quenched disorder, topology and electron correlation.

1. B. Venkatesan et al., npj Quantum Materials 10, 56 (2025).

2. X. Que et al., Nature Communications 16, 3053 (2025).

Brief Bio

Tien-Ming Chuang is an Associate Research Fellow at the Institute of Physics, Academia Sinica. He earned his PhD in Physics from the University of Texas at Austin in 2006, followed by postdoctoral fellowships at Cornell University and the National High Magnetic Field Laboratory between 2007 and 2011. Dr. Chuang joined Academia Sinica in 2011. His research focuses on the microscopic investigation of quantum materials, specifically unconventional superconductors and topological materials, using spectroscopic-imaging scanning tunneling microscopy. He is a recipient of the 2017 Wu Ta-You Memorial Award and the 2012 Kenda Foundation Young Scholar Award.

Mar. 17, 2026 (week 04)

Masaki Azuma

Professor, Institute of Integrated Research, Institute of Science Tokyo

Magnetization Reversal by Electric Field in Co Substituted BiFeO3 Thin Films

Host: Wei-Tin Chen

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Electric field manipulation of magnetization is intensively investigated because of potential application in low-power-consumption non-volatile magnetic memory devises. Ferroelectric BiFeO3 has a cycloidal space-modulated spin structure with a periodicity of 62 nm superimposed on the G-type antiferromagnetic structure which prohibits the appearance of net ferromagnetic magnetization due to spin canting. We have found a spin structure transition from low-temperature cycloidal one to high-temperature collinear one with spontaneous magnetization of 0.03 μB/f.u. confined in a magnetic easy plane perpendicular to the electric polarization is generated by Dzyaloshinskii-Moriya interaction at ~200 K in rhombohedral BiFe1-xCoxO3 [1-3]. (001)pc oriented thin films fabricated by pulsed laser deposition on GdScO3 (110) substrate has out-of-plane component of magnetization which can be observed by magnetic force microscopy (MFM). It is demonstrated that the out-of-plane magnetization can be reversed accompanying electric polarization reversal using piezo response force microscopy (PFM) at room temperature [4]. Magnetization reversal by in-plane electric field was achieved in (110) oriented BFCO film [5]. Changes in ferroelectric and magnetic domains after poling in BiFe0.1Co0.9O3 nanodots with topological domain structures will also be discussed [6,7].

1. H. Yamamoto, T. Kihara, K. Oka, M. Tokunaga, K. Mibu, M. Azuma, J. Phys. Soc. Jpn. 85, 064704 (2016).

2. H. Yamamoto, Y. Sakai, K. Shigematsu, T. Aoyama, T. Kimura, M. Azuma., Inorg. Chem., 56, 15171 (2017).

3. H. Hojo, R. Kawabe, K. Shimizu, H. Yamamoto, K. Mibu, K. Samanta, T. Saha-Dasgupta, M. Azuma, Adv. Mater., 29, 160313 (2017).

4. K. Shimizu, R. Kawabe, H. Hojo, H. Shimizu, H. Yamamoto, M. Katsumata, K. Shigematsu, K. Mibu, Y. Kumagai, F. Oba, M. Azuma, Nano Lett., 19, 1767-177 (2019).

5. T. Itoh, K. Shigematsu, H. Das, P. Meisenheimer, K. Maeda, K. Lee M. Manna, S. P. Reddy, S. Susarla, P. Stevenson, R. Ramesh and M. Azuma, Adv. Mater., 37, 2419580 (2025).

6. K. Ozawa, Y. Nagase, M. Katsumata, K. Shigematsu, M. Azuma, ACS Appl. Mater. Interfaces, 16, 20930 (2024).

7. K. Lee, P. Meisenheimer, P. Stevenson, Y. Nagase, K. Shigematsu, R. Ramesh, M. Azuma, under review.

Brief Bio

After bachelor and master degrees, professor Masaki AZUMA obtained a PhD in chemistry from Kyoto University in 1995. From 1995 to 2010, he was assistant and associate professors at Institute for Chemical Research, Kyoto University and from 2010 he is a professor at Tokyo Institute of Technology which is now Institute of Science Tokyo. He is also a project leader at Kanagawa Institute of Industrial Science and Technology. His interests are related to synthesis, structural analysis and functional properties of advanced oxide materials.

Video

20260319.mp4

Mar. 24, 2026 (week 05)

Chang-Tse Hsieh

Assistant Professor, Department of Physics, National Taiwan University

Why Some Quantum Systems Cannot Be Simple—the Power of Symmetry in Many-Body Physics

Host: Ssu-Yen Huang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

A central theme in modern condensed matter physics is that the collective behavior of many interacting particles can be far richer than what one might infer from single-particle physics alone. In particular, strongly correlated systems often exhibit emergent phenomena governed not by microscopic details, but by more general physical principles. In this talk, I will discuss how symmetry provides a powerful way to constrain the possible low-energy behavior of quantum many-body systems. A classic example is the Lieb-Schultz-Mattis theorem, which shows that certain one-dimensional quantum magnets cannot have a unique gapped ground state if they preserve spin-rotation and lattice-translation symmetries. I will then present recent generalizations of this idea to a broader class of quantum spin systems, illustrating how symmetry can reveal robust features of quantum matter without requiring the full solution of a complicated many-body problem.

Brief Bio

Chang-Tse Hsieh is an Assistant Professor in the Department of Physics at National Taiwan University. He received his PhD in Physics from the University of Illinois Urbana-Champaign in 2017. He subsequently held joint postdoctoral positions at Kavli IPMU and the Institute for Solid State Physics at the University of Tokyo, and later served as a Special Postdoctoral Researcher at RIKEN, before joining NTU in 2022. His research lies in theoretical condensed matter physics and high-energy physics, particularly at their interface. He is primarily interested in topological phenomena, entanglement, and criticality in quantum matter, as well as nonperturbative aspects of many-body systems.

Video

20260324.mp4

Mar. 31, 2026 (week 06)

Li-Chyong Chen

Chair professor, Department of Physics, National Taiwan University

Transition Metal Dichalcogenides as Emerging Photocatalysts for CO2 Reduction

Host: Ssu-Yen Huang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Apr. 7, 2026 (week 07)

Li-Hwai Lin

Research Fellow, Institute of Astronomy and Astrophysics, Academia Sinica

How to Make Galaxies Green?

Host: Shang-Min Tsai

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Green valley (GV) galaxies represent systems transitioning from the star-forming to the quiescent phase and thus serve as ideal laboratories for probing the physical processes that suppress or shut down star formation. In this talk, I will first provide a broader perspective on why understanding galaxy quenching is important, and then present our efforts to address key questions using a combination of state-of-the-art integral field spectroscopy (IFS) surveys and radio observations enabled by the Atacama Large Millimeter/submillimeter Array (ALMA). I will conclude by highlighting directions for future studies.

Brief Bio

Lihwai Lin is a Research Fellow at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan. She received her Ph.D. from National Taiwan University in 2006, followed by a postdoctoral appointment at the University of California, Santa Cruz. She joined ASIAA as a postdoctoral researcher in 2007 and became a faculty member in 2009. Her research focuses on galaxy evolution, particularly galaxy–galaxy mergers and the processes that regulate and ultimately quench star formation across cosmic time. She received the Taiwan Most Promising Young Female Scientist Award in 2023 for her significant contributions to understanding galaxy evolution and large-scale structures. This award is jointly organized by L'Oréal Taiwan and the Wu Chien-shiung Scholarship Foundation to recognize the impact of outstanding female researchers.

Video

20260407.mp4

Apr. 21, 2026 (week 09)

Pin-Jung Chiu

Assistant Professor, Department of Physics, National Taiwan University

First Physics Results from JUNO

Host: Ssu-Yen Huang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kiloton liquid scintillator detector located 700 meters underground in Jiangmen, Guangdong, China. Its primary physics goal is to determine the neutrino mass ordering and to precisely measure the neutrino oscillation parameters by observing fine oscillation structures in the energy spectrum of reactor antineutrinos emitted from two nearby nuclear power plants at a baseline of 53 kilometers. After approximately twelve years of construction and commissioning, JUNO began physics data-taking in August 2025. Using an initial dataset corresponding to 59.1 days of high-quality data, JUNO has reported its first physics results, including precise measurements of two oscillation parameters: sin²𝜃₁₂ = 0.3092 ± 0.0087 and Δ𝑚₂₁² = (7.50 ± 0.12) × 10⁻⁵ eV², achieving world-leading precision. This talk will introduce the JUNO experiment, highlight its detector performance, and present its first physics results and key achievements.

Brief Bio

Pin-Jung Chiu pursued her PhD at the Paul Scherrer Institute (PSI) in Switzerland, where she searched for the neutron electric dipole moment, and received her PhD from ETH Zurich in 2021. She then joined the University of Zurich as a postdoctoral researcher, working on the GERDA and the LEGEND experiments, which search for neutrinoless double beta decay of ⁷⁶Ge. Since February 2025, Pin-Jung Chiu has been an Assistant Professor and a Yushan Young Scholar in the high-energy physics group in the Department of Physics at National Taiwan University. She is currently an active member of both the LEGEND and the JUNO collaborations, two leading neutrino experiments in the world

Video

20260421.mp4

Apr. 28, 2026 (week 10)

Tse-Ming Chen

Professor, Department of Physics, National Cheng Kung University

Engineering Quantum Matter through Geometry:

Twistronics and Straintronics in 2D Materials

Host: Ssu-Yen Huang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Twistronics and straintronics have emerged as powerful approaches for engineering lattice structures and interactions in van der Waals materials, opening new avenues toward quantum phases, emergent phenomena, and novel device functionalities. In this talk, I will present two recent surprising findings in twisted and strained graphene. First, I will discuss how large-angle twisted bilayer graphene, widely assumed to be electronically trivial, can instead develop strong interlayer coupling and unexpected electronic reconstruction in a regime near the crossover between quasicrystalline and commensurate order. Second, I will present how graphene can be transformed into a flat-band, strongly correlated electronic system through our unique strain-engineering strategy, thereby creating opportunities for emergent phenomena and new quantum matters. These results highlight how twist and strain provide complementary and powerful means of reshaping electronic matter, revealing that even seemingly simple graphene can host remarkably rich and unexpected quantum phases when its geometry is strategically designed.

Brief Bio

Tse-Ming Chen is a Professor of Physics and also serves as the Director of the Center for Quantum Frontiers of Research & Technology (QFort) at National Cheng Kung University, where he has been a faculty member since 2010. Tse-Ming received his B.S. and M.S. in Physics from National Taiwan University and his Ph.D. from the University of Cambridge, UK. He has nearly 20 years of experience in low-temperature condensed matter physics, with expertise spanning quantum device design, advanced nanofabrication, and cryogenic dc and rf electrical measurements of nanoarchitectures based on diverse materials including semiconductors, superconductors, two-dimensional materials, topological materials, and complex oxides. His research interests encompass mesoscopic physics, quantum electronics, spintronics, and the engineering of quantum systems.

May 5, 2026 (week 11)

Ching-Hwa Kiang

Associate Professor, Department of Physics and Astronomy, Rice University

Single-Molecule and Single-Cell Force Spectroscopy of Living Matter

Host: Kai-Feng Chen

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Measuring the physical properties of complex, out-of-equilibrium biological systems requires precise nanoscale investigation. At this scale, living matter is governed by rugged energy landscapes that dictate both form and function. Recent advancements in singlemolecule and single-cell dynamic force spectroscopy provide a powerful means to decode this underlying mechanical language. Utilizing atomic force microscopy (AFM), we developed a novel, label-free method to characterize both biomolecular dynamics and cellular states through their unique mechanical and acoustic signatures. By analyzing the force responses of diverse systems, including DNA, multimeric proteins, graphene nanoribbons, and mammalian cells, the thermodynamics of living matter can be directly observed in action. Ultimately, establishing these nanoscale mechanical signatures provides a crucial framework for addressing complex scientific and medical challenges, such as protein folding mechanics and advanced cancer diagnosis.

Brief Bio

Professor Ching-Hwa Kiang is a faculty member in the Department of Physics and Astronomy at Rice University, specializing in experimental biological physics. She earned her BS from National Taiwan University (NTU) and her Ph.D. from the California Institute of Technology (Caltech). While at the IBM Almaden Research Center, she co-discovered single-walled carbon nanotubes and holds a U.S. patent for them. After completing her postdoctoral research at the Massachusetts Institute of Technology (MIT) and working as a visiting scholar at the University of California, Los Angeles (UCLA), she joined the Department of Physics and Astronomy at Rice University. Her current research uses advanced dynamic force spectroscopy techniques to explore fundamental questions in biosystems, including protein and DNA mechanics, virus binding, and cancer research. Professor Kiang is an elected fellow of the American Physical Society and the recipient of the 2007 Best of Small Tech Researcher of the Year award.

Video

20260505.mp4

May 12, 2026 (week 12)

Hauyu Liu

Associate Professor, Department of Physics, National Sun Yat-sen University

The Quest for Planet Formation: Insights from Protoplanetary Disks

Host: Ting-Wen Lan

Time: 2:20 pm ~ 3:30 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Are we alone? You often hear this question because the formation of a terrestrial planet had been, theoretically, considered difficult if not impossible. This was changed after the NASA Kepler and K2 missions found that rocky planets are ubiquitous. Afterwards, it has become popular to resolve the natal environment of rocky planets, the protoplanetary disks, and then investigate the planet-formation activities observationally/theoretically. Without a surprise, most of those studies concluded that the protoplanetary disks we resolved are efficiently forming rocky planets, which, however, yield planets that are too wet and too carbonaceous to compare with our own Earth. Are we not alone? This is the issue I have been tackling. In this talk, I will provide an overview of this research field and outline our contribution/destruction.

Brief Bio

Hauyu Liu is an Associate Professor in the Department of Physics at National Sun Yatsen University (NSYSU). He was awarded Ta-You Wu prize in 2022. He received his Ph.D. in Physics from National Taiwan University in 2012. He served as a postdoctoral fellow at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in 2012-2015, and served as a European Southern Observatory fellow at Garching, Germany, in 2015-2018, before he returned to ASIAA as an Assistant Research Fellow; he became a tenured Associated Research Fellow in 2022. He moved to NSYSU in early 2023. His research broadly covers planet formation, star-formation, some general aspects about the interstellar medium, and the accretion of supermassive black holes, etc, which have been mainly based on the (sub)millimeter and radio interferometry such as the Jansky Very Large Array and the Atacama Millimeter/Submillimeter Array.

May 12, 2026 (week 12)

Lok-Chi Chan

Associate Professor, Department of Philosophy, National Taiwan University

A Philosophical and Legal Reconsideration of Transparency in AI Regulation

Host: Wei-Shu Hou

Time: 3:30 pm ~ 4:30 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

This paper critically examines the concept of transparency in AI systems within the domains of law and governance using tools in philosophy. Current discussions often treat transparency, explainability, and trust as closely linked, frequently requiring explainable AI (XAI) techniques as necessary justifications of AI decisions. Drawing on philosophy, cognitive science, and jurisprudence, we argue in this paper that this approach involves a category mistake: XAI explanations typically describe causal mechanisms or computational processes, which are levels below that of propositional justification expected in human deliberation, including human legal and theoretical reasoning. It concludes that transparency should be understood as a requirement in social dilbeberation rather than a purely technical feature of AI systems. Accordingly, the paper proposes a pluralistic, context-sensitive approach to AI transparency informed by analogies with existing legal and regulatory practices, with XAI serving as a useful but neither necessary nor sufficient tool.

Brief Bio

Lok-Chi Chan (陳樂知) is an Associate Professor of Philosophy at National Taiwan University. He acquired his PhD from the University of Sydney in 2017, following a First Class BA Honours from Monash University in 2011. His academic focus lies in several philosophical areas including the philosophy of mind, metaphysics, and philosophy of religion, with a particular focus on exploring the nature of our current scientific worldview. His research has been published in a number of top and leading international philosophy journals and has received several local and international awards. He currently also serves as the Co-director of National Taiwan University's Center for Traditional and Scientific Metaphysics (TSM Center) and the Vice President of the Asian Society for Philosophy of Religion.

Video

20260512.mp4

May 19, 2026 (week 13)

Ming-Chang Chen

Associate Professor, Institute of Photonics Technologies, National Tsing Hua University

Watching Electrons Move: The Frontiers of Attosecond Physics

Host: Cheng-Tien Chiang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

Attosecond science enables direct observation of electron motion on its natural timescale. In this talk, I will present our recent progress in developing turn-key tabletop coherent extreme-ultraviolet (EUV) and isolated attosecond light sources driven by post-compressed ytterbium lasers. By combining cascaded postcompression and filamentation-assisted high-harmonic generation, we demonstrated isolated attosecond pulses in the sub-100-attosecond regime. I will discuss how waveform-controlled light fields enable studies of ultrafast electron, spin, and charge-transfer dynamics, as well as recent advances in EUV spectroscopy and metrology for probing quantum materials and strong-field physics.

Brief Bio

Dr. Ming-Chang Chen is an Associate Professor at the Institute of Photonics Technologies, National Tsing Hua University, Taiwan, where he leads the

ATTO–EUV Laboratory. He received his Ph.D. in Physics from the University of Colorado Boulder in 2012 and previously conducted research at JILA and TU Wien. His research focuses on ultrafast optics, attosecond science, coherent EUV light sources, and strong-field physics. His group develops

tabletop attosecond-EUV platforms for ultrafast spectroscopy and EUV metrology.

Video

20260519.mp4

May 26, 2026 (week 14)

Shun-Jen Cheng

Professor, Department of Electrophysics, National Yang Ming Chiao Tung University

Momentum Excitons in 2D Materials

Host: Cheng-Tien Chiang

Time: 2:20 pm ~ 4:20 pm

Place: Chin-Pao Yang Lecture Hall, R104, CCMS-New Phys. building

Abstract

In this work, I will review our recent progress in the research on exciton complexes in 2D materials. Specifically, the research is focused on momentum exciton in transition metal dichalcogenide monolayers, including intravalley finite momentum exciton and intervalley momentum forbidden dark exciton. Despite the optically dark nature, we shall show that momentum excitons play an essential roles in several fascinating optoelectric phenomena, such as energy transfer in near field optics, structured-light-exciton interaction, and upconversion photoluminescence via exciton-exciton annihilation.

Brief Bio

Shun-Jen Cheng received his Dr. rar. nat. degree in physics from the University of Würzburg, Germany, in 2001. He is currently a full professor at the Department of Electrophysics of National Yang Ming Chiao Tung University (NYCU). His theoretical and computational research on low-dimensional systems covers the wide aspects of physics in nano-sciences, from the electronic structures, exciton physics, photonics to magnetism. His recent research is focused on the exciton fine structures of transitional metal dichalcogenide monolayers and the photoexcitation of exciton by twisted lights with quantized orbital angular momenta. The quantum solid-state theory group led by Prof. Cheng at NYCU has recently accomplished an advanced computational platform based on the first principles density-functional-theory and Bethe-Salpeter equation in the Wannier tight binding scheme, enabling the efficient and quantitatively valid calculations of full-zone exciton fine structures of 2D materials.

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