## Plenary Speakers

*Lionel Ni*

University of MacauUniversity of Macau

*Homepage*# Talk Title: Big Data Meets Physics

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**Abstract:**

Big Data is having a tremendous impact on many important areas of physics. Big Data analytics not only help physicists automatically design counterintuitive experiments, but also revolutionize old-school analytical approaches and open myriad opportunities for novel discoveries with unexpected properties in physics. For example, particle physicists now cooperate with artificial intelligence experts to discover new particles in the next generation of particle-collider experiments. Major achievements by Big Data analytics are transforming our life across multiple domains. However, as the amount of data is exploding on an unprecedented scale, conventional computers or even the most powerful supercomputers existing today are becoming inefficient in processing the enormous data. The advent of quantum computers shows huge potential for tackling this problem, having achieved some initial successes. In this talk, the innumerable sparks that fly between Big Data and Physics will be presented.

*Shiyi Chen*

South University of Science and Technology of ChinaSouth University of Science and Technology of China

*Homepage*#
Talk Title: to be updated

# Abstract:

To be updated.

*Xiantu He*

Institute of Applied Physics and Computational MathematicsInstitute of Applied Physics and Computational Mathematics

*Homepage*#
Talk Title: Warm Dense Matter Properties under Conditions of High Energy Density

# Abstract:

Warm dense matter (WDM) is a state between conventional condensed matter and plasmas that cannot be satisfactorily described by standard theory. Matter densities are in the range of ~1-1000g/cc, temperatures are comparable to the Fermi energy and above, and pressure consequently large. The study of WDM is crucial for understanding the evolution of large planets, inertial confinement fusion (ICF) dynamics and the earth mantle, and the transition of matter from a condensed state to a high energy density (HED) state, where molecular, atomic, and ionic interactions are all important, which theory and experiment are extremely challenging.

In this presentation, we report the quantum statistical characteristics of WDM, involving screen effects, pressure ionization and continuum lowering of ionization energy, plasma phase transition, self-energy calculation, etc. Using numerical simulations, we further investigate their partial degenerate properties, transport coefficients (electric and thermal conductivities), equation of state under conditions of LTE.

*Che Ting Chan*

Hong Kong University of Science and TechnologyHong Kong University of Science and Technology

*Homepage*#
Talk Title: Computational Approach to Wave Functional Materials

# Abstract:

The study of electromagnetic and acoustic waves dates back to the antiquities and their diverse applications form the very pillars of modern technology. Revolutionary ideas start to emerge in this classic field about two decades ago, and these new notions made possible the realization of man-made materials with wave manipulation functionalities beyond the defined limits of those found in nature. These novel functional materials include photonic/phononic crystals, metamaterials and plasmonic structures. We will give some examples to show how computational physics can be used to design new artificial materials that can make possible some novel effects that were previously thought to be impossible. I will begin by explaining what these materials are and what they can do. I will then give examples to show that subwavelength microstructures can induce invisibility, optical illusion, extreme effective parameters (such as zero-refractive index), artificial magnetic fields, geometric phases, one-way transport, topological states and topological points in the momentum space. We shall emphasize the importance and power of computation, as most of these problems cannot be solved analytically. These new functional materials also cannot be made by empirical cut-and-try methods without a careful and rational design on the computer.

*Yuan Ping Feng*

National University of SingaporeNational University of Singapore

*Homepage*#
Talk Title: Spintronics Based on 2D Materials – First Principles Explorations

# Abstract:

Spintronics is considered a promising direction for the future of electronics. The key issues of realizing spintronics are identification of materials which allow generation, manipulation and detection of spin states, as well as injection of spin from one material to another. Two-dimensional (2D) materials have been extensively studied and some of them show promising application potentials. Computational approach, particularly that based on first-principles electronic structure calculation, is play an important role in predicting materials for spintronics applications. We will review latest developments in first-principles prediction of 2D spintronic materials and devices, and some of our recent works on graphene, phosphorene, etc.

*Enge Wang*

Chinese Academy of Sciences and Peking UniversityChinese Academy of Sciences and Peking University

*Homepage*#
Talk Title: Quantum Nature of Water on Salt Surface

# Abstract:

Water-solid interactions are of broad importance in nature and technology. Using a combination of ab initio path-integral molecular dynamics, in which the quantum behaviors of the nuclei are addressed, and tip-enhanced inelastic electron tunneling spectroscopy based on a scanning tunneling microscope, we systematically studied the mechanisms of water clustering, proton transfer, and the quantum nature of water hydrogen bond on salt surface. An extended 2D ice layer based on tetramers interconnected by bridging water molecules was identified on NaCl (001) [1], which processes substantial breaking down of the conventional Bernal-Fowler-Pauling ice rule. And a concerted proton tunneling mechanism was observed within the water tetramer, when it is isolated [2]. By comparing with the inelastic electron tunneling spectroscopy experiment, the quantum nature of hydrogen bond was also illustrated. These simulations provide detailed atomic level information for the accompanied cryogenic scanning tunneling microscope experiments, which would be helpful in understanding/designing novel water/solid interface structures and utilizing such structures for the study of water clustering and concerted proton tunneling in more complicated systems [3].

[1] J.Chen, J.Guo, X.Z.Meng, J.B.Peng, J.M.Sheng, L.M.Xu, Y.Jiang, X.Z.Li, and E.G.Wang, Nat. Commun. 5, 4056 (2014)

[2] X.Z.Meng, J.Guo, J.B.Peng, J Chen, Z.C.Wang, J.R.Shi, X.Z.Li, E.G.Wang, and Y.Jiang, Nat. Phys.11, 235 (2015)

[3] J. Guo, J. T. Lü, Y. X. Feng, J. Chen, J. B. Peng, X. Z. Meng, Z. C. Wang, Z. R. Lin, X. Z. Li, E. G. Wang, Y. Jiang, Science 352, 321(2016).

*Mei-Yin Chou*

Institute of Atomic and Molecular Sciences of Academia SinicaInstitute of Atomic and Molecular Sciences of Academia Sinica

*Homepage*#
Talk Title: Computational Studies of Novel Two-Dimensional Materials and their Heterostructures

# Abstract:

It has become possible in recent years to fabricate and manipulate two-dimensional nanomaterials in the laboratory that are as thin as one to few atomic layers. The reduced dimensionality gives rise to unique physical and chemical properties that differ from those of traditional bulk materials, and intriguing physical properties have been found in these few-layer systems. Computational studies have played a central role in understanding and predicting these novel properties. In this talk, I will focus on a few representative systems, including twisted bilayer graphene and monolayers of transition metal dichalcogenides that exhibit properties ranging from normal semiconductors to charge density waves to superconductivity. I will report on our recent theoretical and computational studies to explore the connections among charging, lattice distortion, electronic properties, charge density waves, and superconductivity. In addition, I will discuss how the Moiré patterns in van der Waals heterostructures modify the local electronic properties and structural parameters..

*Steven G. Louie*

University of California at BerkeleyUniversity of California at Berkeley

*Homepage*#
Talk Title: Novel Phenomena in Quasi Two-Dimensional Materials: A First-Principles Perspective

# Abstract:

Atomically thin quasi two-dimensional (2D) materials and their nanostructures can exhibit highly unusual behaviors. Owing to their reduced dimensionality, these systems present opportunities for manifestation of concepts and phenomena that may not be so prominent or have not been seen in bulk materials. Symmetry, many-body interaction, doping, and substrate screening effects typically play a critical role in shaping qualitatively and quantitatively their properties, and thus their potential for applications. Accurate treatment of these effects, in particular many-electron interactions, in quasi 2D materials poses new theoretical and computational challenges. In this talk, we present some first-principles studies on monolayer and few-layer transition metal dichalcogenides and metal monochalcogenides, as well as graphene, black phosphorus and other 2D crystals. Several highly interesting and unexpected phenomena are discussed: novel exciton behaviors; tunable transport, optical, magnetic and plasmonic properties; and the dominant influence of substrate screening. We investigate their physical origin and compare computed predictions with experimental results.

This work was supported in part by the National Science Foundation and the U.S. Department of Energy.

*Jian-Wei Pan*

Hefei National Laboratory for Physical Sciences at the Microscale, USTCHefei National Laboratory for Physical Sciences at the Microscale, USTC

*Homepage*#
Talk Title: Scalable quantum information processing with photons and atoms

# Abstract:

Over the past three decades, the promises of super-fast quantum computing and secure quantum cryptography have spurred a world-wide interest in quantum information, generating fascinating quantum technologies for coherent manipulation of individual quantum systems. However, the distance of fiber-based quantum communications is limited due to intrinsic fiber loss and decreasing of entanglement quality. Moreover, probabilistic single-photon source and entanglement source demand exponentially increased overheads for scalable quantum information processing. To overcome these problems, we are taking two paths in parallel: quantum repeaters and through satellite. We used the decoy-state QKD protocol to close the loophole of imperfect photon source, and used the measurement-device-independent QKD protocol to close the loophole of imperfect photon detectors—two main loopholes in quantum cryptograph. Based on these techniques, we are now building world’s biggest quantum secure communication backbone, from Beijing to Shanghai, with a distance exceeding 2000 km. Meanwhile, we are developing practically useful quantum repeaters that combine entanglement swapping, entanglement purification, and quantum memory for the ultra-long distance quantum communication. The second line is satellite-based global quantum communication, taking advantage of the negligible photon loss and decoherence in the atmosphere. We realized teleportation and entanglement distribution over 100 km, and later on a rapidly moving platform. We are also making efforts toward the generation of multiphoton entanglement and its use in teleportation of multiple properties of a single quantum particle, topological error correction, quantum algorithms for solving systems of linear equations and machine learning. Finally, I will talk about our recent experiments on quantum simulations on ultracold atoms. On the one hand, by applying an optical Raman lattice technique, we realized a two-dimensional spin-obit (SO) coupling and topological bands with ultracold bosonic atoms. A controllable crossover between 2D and 1D SO couplings is studied, and the SO effects and nontrivial band topology are observe. On the other hand, utilizing a two-dimensional spin-dependent optical superlattice and a single layer of atom cloud, we directly observed the four-body ring-exchange coupling and the Anyonic fractional statistics. .

*Jisoon Ihm*

Pohang University of Science and Technology, Republic of KoreaPohang University of Science and Technology, Republic of Korea

*Homepage*# Talk Title: Manifestation of Axion Electrodynamics on Topological

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**Abstract:**

Topological surface states of a single TI crystal can exist on different surfaces with different work functions, and mutual interactions between them through edges may give rise to novel electromagnetic phenomena. In this talk, the basic idea of topological insulators is given at first. Then the results of first-principles electronic structure calculations as well as the theory of the axion electrodynamics are presented. Our calculations for Bi2Se3 indicate that [1] the difference in the work function between different crystal-face orientations generates a built-in electric field around facet edges and lines of effective magnetic dipoles are accumulated at those edges for a given broken time-reversal symmetry. The predicted magnetic ordering depending only on the work function differences between facets would be a unique manifestation of the axion electrodynamics (in particle physics theory) in real solids and suggests a route to reveal novel electric and magnetic properties of macroscopic topological edge states of a TI.

*Robert A. DiStasio*

Cornell University, Department of Chemistry and Chemical BiologyCornell University, Department of Chemistry and Chemical Biology

*Homepage*# Talk Title: First Principles Approaches for Intermolecular Interactions: From Gas-Phase Dimers to Liquid Water and Molecular Crystal Polymorphism

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**Abstract:**

In this work, I will present an accurate and efficient method for obtaining a first-principles based theoretical description of non-bonded van der Waals (vdW or dispersion) interactions that includes both long-range Coulomb electrodynamic response screening effects as well as treatment of the many-body vdW energy to infinite order. The resulting many-body dispersion (MBD) model goes well beyond the standard pairwise-additive approximation for treating vdW interactions and can easily be coupled to a wide array of theoretical methods, ranging from classical force fields to higher-level quantum chemical calculations. To demonstrate the increasingly important role played by many-body vdW interactions in large, structurally complex molecular systems, we use this method to investigate several pertinent molecular properties, such as binding energies/affinities in gas-phase molecular dimers and supramolecular complexes, relative conformational energetics in small polypeptides, the equilibrium structure and anomalous density properties of liquid water, and thermodynamic stabilities among competing molecular crystal polymorphs.

*Hui Pan*

Institute of Applied Physics and Materials Engineering, University of MacauInstitute of Applied Physics and Materials Engineering, University of Macau

*Homepage*# Talk Title: Materials Design for Hydrogen Production from Water

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**Abstract:**

In the talk, I will present the design of materials for hydrogen production by splitting water, including solar-driven water splitting and electrolysis of water, based on first-principles calculations. For solar-driven water splitting, a new “noncompensated” codoping concept was proposed to engineer the electronic structure of TiO2. The approach enables controllable narrowing of the TiO2 band gap with significantly enhanced carrier mobility and photocatalytic activity in the visible light region and thus offers immense potential for application in solar energy conversion, water splitting, and a variety of solar-assisted photocatalysis. For electrolysis of water, novel, abundant, cheap electrocatalysts, including 2D MX2, MXenes, and nanowires, will be discussed. (1) We find that metal disulfide monolayers show better catalytic performance on hydrogen production than other metal dichalcogenides. (2) We show that the catalytic performance of Ni3S2 nanowire in hydrogen evolution reaction (HER) can be greatly improved by vanadium doping. (3) We predicted that MXenes can be another possible candidate to replace Pt as electrocatalyst in HER. Some of the predictions were realized in experiments.