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The School of Physics at Nankai University
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The School of Physics at Nankai University

YAN'AN LUO
SCHOOL OF PHYSICS, NANKAI UNIVERSITY, CHINA

NANKAI UNIVERSITY

In 1919, with the assistance of individuals from diverse backgrounds, Nankai University was founded by the patriotic educators Mr. Boling Zhang and Mr. Fansun Yan on the principles of art to regulate the country, science to strengthen the country, and business to richen the country. Combining the Chinese experience for its academic setting with Western modes of school operations, Nankai University focused on solving domestic problems as its educational objective. In the 1920s and 1930s, Nankai University grew to be the most famous private university in China.

Ever since its foundation, the university has held as its objective the well-balanced development of morality, intelligence, physical education and art. In accordance with its motto of dedication to the public's interests, acquisition of well-rounded capabilities and aspiration for daily progress, the university has been committed to cultivating the students' civic virtues of patriotism and collectivism, and developing their abilities to serve the country. The university is proud to have as alumni prominent individuals such as the late Premier Enlai Zhou, Dr. Shing-shen Chen, Dr. Ta-you Wu and the playwright Yu Cao.


Fig. 1: The Main Building of Nankai University and the statue of Zhou Enlai.

Nankai University now occupies an area of 4,489,700 m² with floor space of up to 1,368,000 m². The total collection of the university library reaches 3,581,000 volumes and 30 TB e-books. In addition to its main campus, which is located in Balitai, Nankai University also has campuses in the Jinnan District, and TEDA College in the Tianjin Economic-Technological Development Area. Supported by the Ministry of Education, the campus in Jinnan has come into service. Nankai University has a full-fledged education system for producing undergraduates, graduate students in master's and doctoral programs and post-doctoral researchers. Currently, the university has a total enrollment of 24,525 students, including 13,067 undergraduate students; 8,162 master's candidates; 3,296 doctoral candidates; 1,048 foreign students; 2,786 part-time adult students and 43,037 students in the distance education program.

SCHOOL OF PHYSICS

The Physics Department was one of the earliest disciplines in Nankai University, which was founded in 1919. The famous physicist, Professor Dayou Wu, has taught in the department and Nobel Prize winners Professor Chen-Ning Yang and Professor Tsung-Dao Lee are honorary professors of the school. The school has impressive achievements in teaching and research. In the last five years, it has taken more than 200 projects, including 14 "973 Program" (National Basic Research) projects, one "863 Program" (State High-Tech Development Plan) project, 90 National Natural Science Foundation projects, more than 20 officially published books and has won more than 40 national and ministerial scientific, technological and teaching awards. The experimental physics teaching center of school is a national experimental teaching demonstration center, and the experimental physics teaching team is awarded as a national teaching team.

The school has three undergraduate majors: physics, optical information science and engineering, and applied physics. The school not only provides good learning conditions for students, but also provides an inclusive environment for the development of their abilities, including the students' independent organization of the "Physics Today" lecture series, academic competitions, an undergraduate innovative engineering program, a mathematical modeling competition, scientific research practicums, and opportunities for volunteering and public outreach.


Fig. 2: The building of the School of Physics, Nankai University.

In the past nine decades, the school has experienced a colorful and fruitful, but hard and complicated course. The teaching ideology of the school is teaching and scientific research. The school not only pays attention to basic theoretical knowledge, but also focuses on the cultivation of the students' practical abilities. Each major has common basic courses, including foreign languages, mathematics, theoretical mechanics, thermodynamics, electromagnetism, optics, atomic physics, basic physics experiments and modern physics experiments.

FACULTY

The School of Physics has more than 100 teachers, including 45 professors and 31 associate professors. Among the faculty numbers, one is an academician of the Chinese Academy of Sciences, four were the winners of the "Chang Jiang Scholar Award Project" issued by the Ministry of Education, six were recipients of the "National Science Fund for Distinguished Young Scholars", 4 were given awards for "Cross Century Talent" and 17 were given awards for "New Century Talent".

In addition to cooperation in domestic academic facilities, the school has also fostered international collaborations with famous international universities such as Vienna University, Clausthal University of Technology, Münster University, Osnabrück University, the University of Bonn, the Josef Stefan Institute of Ljubljana, the University of Ljubljana, the University of Electro-Communications, the National Institute for Research in Inorganic Materials, the Russian Academy of Science, Kiew Institute of Physics of the National Academy of Sciences, Stanford University, Purdue University, Tampere University of Technology, etc.

RESEARCH AND HIGHLIGHTS

(1) Theoretical Physics

The theoretical physics group at Nankai University was established in 1956. Now it has 23 faculty members, including 19 full professors and four associate professors. Among the faculty members, there is an academician of the Chinese Academy of Sciences, two National Outstanding Young Researchers, and two National Thousand Young Talents researchers. The research areas in theoretical physics can be characterized as follows: mathematical physics and quantum field theory, particle and nuclear physics; quantum information and quantum computing; and nonlinear science. The faculty and their students have been undertaking many national research projects, and yearly publish many papers in high impact journals such as Physical Review Letters.

High Energy Physics: BEPCII/BESIII is a large-scale scientific experimental facility, studying hadron spectroscopy and τ-charm physics. Since joining the BESIII collaboration, Nankai University has made many contributions in other fields, especially in charmonium spectroscopy. Below the open-charm threshold, the spin-singlet state hc is not well understood. The resonant parameters of hc is measured precisely by the process of ψ´ → π0 hc, hc → γ ηc, which provides unique information about spin-spin interaction between heavy quarks. In the quark model, one quark and one anti-quark form mesons while three quarks form baryons. However, hadronic states with other configurations is of great interest because it is also allowed by quantum chromodynamics (QCD). No solid experimental evidence was found, however, until the recent observation of the charged charmonium-like state Zc(3900). After that, via the process e+e- → π+π- hc and e+e- → π0π0 hc, a new charmonium-like state Zc(4020)+/- and its iso-spin partner Zc(4020)0 have been observed in the invariant mass of π hc. It is the first iso-spin triplet charmonium-like state established experimentally and the measured properties support the hybrid explanation. These results are crucial to understand the nature of Zc and even other XYZ particles [Phys. Rev. Lett. 111, 242001 (2013), Phys. Rev. Lett. 113, 212002 (2014)].


Fig. 3: The sum of the simultaneous fit to the π hc mass distribution is shown in the plots, left and right being charge and neutral Zc(4020) respectively.

Quantum Physics: The complexity of matter, arising from an enormous number of atoms and the balance of the competing inner or outer forces, hinders the attempts to provide clear descriptions for the state of matter. We need to think about new theoretical methods that are better able to accommodate this complexity. Recently, Zhi Song's group explored a quantum spin system that possesses a rich phase diagram and developed a new method to characterize the properties of the system [Phys. Rev. Lett. 115, 177204 (2015)]. They introduced a two-dimensional graph to encode the complete information of the system given by the exact wave functions and spectrum. They found that the quantum phase transitions can be realized by simply scanning the geometric topology of the 2D graph, which is indicated by a winding number (Fig. 4). Their finding could inspire new methods to sketch more complicated systems. Historically, an important step in this direction was the creation of the Feynman diagrams, which give a simple visualization of what would otherwise be a rather arcane and abstract formula.


Fig. 4: Several types of graphs. The circles 0, 1, 2 represent different kinds of Ising models.

We know that the application of masers is limited by demanding working conditions (i.e., high vacuum or low temperature conditions). A room-temperature solid-state maser is highly desirable. Recently, Liang Jin and co-workers proposed a diamond maser that can operate at room temperature based on the nitrogen-vacancy (NV) centers in diamonds [Nature Commun. 6, 8251 (2015)]. In their setup, a size 3×3×0.5 mm3 diamond with NV center concentration of 2 ppm is placed inside a cylindrical sapphire dielectric microwave resonator with Q-factor 5×104; the NV centers under a uniform magnetic field resonantly couple to the microwave cavity. They demonstrated that under 532 nm laser pump power less than 10 W, the maser output power is larger than 10 nW and the coherence time reaches minutes.

(2) Condensed Matter Physics

The condensed matter physics group at Nankai University was founded in 1977 and mainly focuses on solid state spectra and crystal physics. A LiTaO3 single crystal was first grown in China and the optical damage resistance of a highly Mg-doped LiNbO3 (LN:Mg) crystal was found to be two orders of magnitude higher than that of a nominally pure one; the LN:Mg crystal has been called the "Star of China". Recently, the strong optical damage resistance in UV-region of Zr-doped LiNbO3 has been selected as research highlight in Nature Photonics 4, 128 (2010). The Tianjin Key Laboratory of Photonics Materials and Technology for Information Science was founded in 2003. The faculty has 28 teachers, including 13 professors and 5 senior engineers. The research fields are as follows: functional material physics; soft condensed matter physics; computational physics; life information physics; and low dimensional materials and devices.

Soft Condensed Matter: This area of research includes the self-assembly, phases and phase transitions of block copolymers under confinement and in solutions, conformations and the related phase transitions of polyelectrolytes. Block copolymers are a class of soft matter that self-assembles to form ordered morphologies on nanometer length scales, making them ideal materials for various applications. The self-assembly of block copolymers is mainly controlled by the monomer-monomer interactions, block compositions and molecular architectures. Besides these intrinsic parameters, placing block copolymers under confinement or in a solution introduces a number of extrinsic factors, which can strongly influence the self-assembled morphologies and therefore can provide powerful routes to manipulate the self-assembled nanostructures of block copolymers. We systematically investigated the self-assembled nanostructures of block copolymers under 2D- and 3D-confinement. It was found that a very rich array of nanoscopic structures can be formed from block copolymers under 2D- and 3D-confinement. Most of these structures are not accessible in bulk or in 1D-confined systems [Phys. Rev. Lett., 96,138306 (2006)]. Mechanisms of structure formation and morphological transitions were elucidated by analyzing the degree of commensurability between the pore diameter and bulk period of the copolymer. Based on the large number of studies from our group and from the literature, we deduced some general observations about the structural formation of diblock copolymers under confinement. In particular, we obtained a number of generic rules of controlling the morphologies as a function of geometric and energetic considerations, and the relationship between the confining conditions and the resulting structures. We also systematically investigated the self-assembled nanostructures of block copolymers, as well as grafted block copolymers, in different types of solvents, and elucidated mechanisms of structure formation and morphological transitions. We also systematically studied the nature of coil-globule transitions and scaling behavior of a strongly-charged polyelectrolyte chain in a solution system. The results reveal that at the thermodynamic limit of an infinitely long chain length, the coil-globule transition may remain first-order, and the exponent v of the radius of gyration, <Rg2> ~ N2ν, can be slightly larger than 1 under some conditions.


Fig. 5: Typical structures obtained for diblock copolymers as a function of volume fraction and confinement.

Computational Physics: We are currently interested in the synthesis and characterization of borophene, which is a cousin of graphene. Borophene had been predicted more than 10 years ago, but has not been successfully synthesized so far. Several boron samples exist, such as thin films or small planar clusters; however, they are extremely difficult to be characterized due to their structural complexity, and consequently the characterization of borophene remains one of the most distinguished open questions in condensed matter physics. An international team led by Prof. Xiang-Feng Zhou and Prof. Hui-Tian Wang at Nankai University, and Prof. Artem R. Oganov at Stony Brook University, predicted a novel 2D-boron which could exhibit massless Dirac fermions with anisotropic Dirac cones, i.e. that the transport properties of these Dirac fermions would depend on direction, which would give an additional degree of freedom for electronic applications [Phys. Rev. Lett. 112, 085502 (2014)]. This work further stimulates experimentalists to challenge the realization of borophene or boron sheets. Fortunately, scientists from Argonne National Lab, Northwestern University, Stony Brook University, and Nankai University collaborated closely to achieve a major breakthrough by growing atomic borophene on an Ag (111) surface under ultrahigh-vacuum (UHV) conditions [Science 350, 1513 (2015)]. The experiment combined with the theory show that this stable, atomic borophene displays remarkable properties. For example, calculations reveal that it has an anisotropic conductivity, and possesses a rarely seen "negative Poisson's ratio" (i.e., tensile strain results in an unusual expansion along its perpendicular direction). Meanwhile, its in-plane Young's modulus (a measure of stiffness) is equal to 398 GPa·nm along the axis, which potentially rivals graphene (the hardest 2D material), at 340 GPa·nm.


Fig. 6: (a) illustration of two dimensional (2D) Dirac boron, (b) atomic borophene.

(3) Optics

The study of optics in Nankai University is one of the earliest and strongest bases for optical research and talent training in China. Prof. Yutai Yao and Prof. Dayu Wu have taught optics before the liberation and Prof. Shouchun Shen and Prof. Guoguang Mu lead the foundation of optics discipline in Nankai University after the liberation. The early research fields include optical instruments, optical information processes, spectra techniques and laser techniques. Now Optics in Nankai University is a National Key Discipline, including the Key Laboratory of the Ministry of Education for Low-Intensity Nonlinear Photonics and the Collaborative Innovation Center of Extreme Optics. The faculty has 44 teachers including 20 professors. The research fields are as following: Nonlinear optics, Micro-nano scale photonics, Ultrafast photonics, Quantum Photonics, Novel Fluorescent Materials and Devices, Glass and Fiber, and Optical Fields.

Metamaterials: Artificial composite structures with exotic material properties have emerged as a new frontier of science involving physics, material science, engineering and chemistry. The rapidly growing metamaterials research is driven by a number of potential applications of metamaterials. Our research mainly focuses on the applications in perfect absorption, manipulating nanoscale localized fields by composite metameterials, electromagnetically induced transparency (EIT), super-resolution imaging and so on [Adv. Mater. 27, 5410 (2015)].

Graphene Optics: Although material innovation provides numerous and exciting new opportunities, scientists and engineers are facing formidable challenges at the same time ranging from high quality material synthesis and novel device realization, to high performance system integration. We try to address these challenges in our group. Here we explore basic properties of emerging two-dimensional materials such as graphene, transition metal dichalcogenides (TMDCs), boron nitride and black phosphorous; build functional devices based on these materials; and identify their applications in photonics and electronics. (1) We fabricated twist-controlled BLG and double-twisted trilayer graphene (DTTG) with high precision and investigated their controllable optoelectronic properties for the first time [Adv. Mater. (2016)]. (2) We obtained a highly sensitive graphene optical sensor with label-free, live-cell, and highly accurate detection of a small quantity of cancer cells among normal cells at the single-cell level [Nano Lett. 14, 3563 (2014)]. (3) We achieved the large enhancement of optical limiting effects in three covalently functionalized SWNTs with porphyrins [Adv. Mater. 20, 511 (2008)].


Fig. 7: Double-twisted trilayer graphene (left) and highly sensitive graphene optical sensor (right).

Photonic grapheme: Graphene, a two-dimensional (2D) honeycomb lattice of carbon atoms, has been highly touted and tested for many applications in recent years, apart from elucidating fundamental phenomena in quantum and condensed matter physics. "Photonic graphene", an artificial honeycomb array of evanescently coupled waveguides, has proven to be a useful tool for studying graphene physics in various optical settings. Since photonic lattices offer exquisite control over initial conditions and allow for monitoring the actual wavefunction (including phase), and it is possible to directly observe graphene wave dynamics using classical light waves in regimes difficult or inaccessible for natural graphene. In our recent work, we have experimentally demonstrated a host of novel phenomena including unconventional edge states and pseudospin-mediated vortex generation in optically induced photonic graphene systems [Nat. Commun. 6, 6272 (2015), Nat. Mater. 13, 57 (2014)]. These results also have an impact on other artificial graphene systems beyond optics.


Fig. 8: Schematic of the lattice and band structure of the honeycomb lattice.

SUMMARY AND PROSPECTS

In summary, the School of Physics has been in a period of great expansion and development in the past two decades. In order to further improve the quality and structure of the faculty, the school is now expanding its scope of research and is seeking a number of outstanding new faculty members for its newly launched, highly competitive and well-funded "Hundred Youth Academic Leader Program" at all the professorial levels in areas of theoretical physics, condensed matter physics, optics and photonics. For more and updated information, please visit our website: http://physics.nankai.edu.cn.

 

Yan'an Luo is a professor of physics and is currently the dean of the School of Physics at Nankai University. He received his PhD from Nanjing University in 1998 and subsequently joined Nankai University. He worked in France and in the USA from 2001 to 2004. His research interest is theoretical nuclear physics.