New Quantum Materials and Transport

I. Coordinator:
  • Feng-Chuan Chuang 莊豐權 (NSYSU) and Horng-Tay Jeng 鄭弘泰 (NTHU)

II. Core Members:

  • Core members
  • Chao-Cheng Kaun 關肇正 (AS), Hsin Lin 林新 (AS), Chih-Kai Yang 楊志開 (NCCU), Tsan-Chuen Leung 梁贊全 (Natl Chung Cheng Univ), Shi-Hsin Lin 林仕鑫 (NSYSU, young researchers) and Tay-Rong Chang 張泰榕 (NCKU, young researchers)
  • Young Participants
  • Postdocs
  • Zhi-Quan Huang 黃志權 (NSYSU), Chia-Hsiu Hsu許嘉修 (NSYSU), Chi-Hsiung Lee 李啟玄 (NCCU), Te-Hsien Wang王德賢(NTHU), and Hung-Lung Huang黃鴻隆 (NTHU), Mathan Kumar (AS)
  • Ph. D. Students
  • Gennevieve Macam (NSYSU), Rovi Angelo Villaos (NSYSU), Angus Huang黃彥哲 (NTHU), Sheng-Hsiung Hung洪聖雄 (NTHU), Kai-Wei Chang張凱維 (A S-TIGP), Han Hu胡瀚 (NCCU), Kuan-Bo Lin林冠伯 (NCKU), Guanwei Peng彭冠瑋 (NTU)
  • M.S. Students
  • Liang-Ying Feng 馮亮穎(NSYSU), Yi-Chun Chen 陳奕鈞(NSYSU), Mei-Ling Xu許美玲(NSYSU), Harvey Cruzado (NSYSU), Aniceto Maghirang III (NSYSU), and John Symon Dizon (NSYSU), Chin-Hsuan Chen 陳錦軒 (NTHU), Jo-Hsueh Lee 李若瑄 (NSYSU), Wan-Jou Chou 周宛柔 (NSYSU), Guan-Fu Chen 陳冠甫 (NSYSU), Sylvia Q. Cai 蔡晴羽 (NTNU), Yi-Hsing Yu 余宜馨 (NCKU), 何顯龍 (NTHU), 陳柏宇 (NTHU), Hui-Wen Tsao 曹惠雯 (NCKU), Yung-Sheng Chen 陳詠升 (CCU),Ka Hou Ung 吳家浩(CCU),Chuan-Sheng Kao 高川勝(CCU),Chih Teng 鄧至(CCU)

III. Research Themes:

  • The research proposal of this thematic group (TG) of 2019-2020 is primarily to study and to predict novel topological materials and advanced two-dimensional (2D) materials based on first-principles calculations and tight-binding model. This 2019-2020 thematic group and its core members are trimmed and reorganized from the previous thematic group of New Quantum and Transport Materials in NCTS Phase IV (2015-2016) and previous focus group of computational material research (CMR) in NCTS Phases II and III. The core members of this TG endeavor earnestly to collaborative frontier research projects with common interests in the computational research. By utilizing ab initio computation tools coupled with other theoretical/computational methods, we hope to establish new combinations of approaches, expanding the scope of applicability and pushing accurate prediction for novel important properties in topological and advanced 2D materials. Topological materials have become one of the fast growing research topics in the world. Topological insulators contribute to electrical conduction through their surface states protected by time-reversal and/or crystalline symmetry and provide dissipationless spinpolarized transport. We divide our manpower to tackle the research problems of topological materials by dimensionality.
  • Two-dimensional topological materials:
  • (C.-K. Yang楊志開, T. C. Leung 梁贊全, S.H. Lin 林仕鑫, Hsin Lin 林新 and F.-C. Chuang 莊豐權)
    Two-dimensional topological materials (e.g., quantum spin Hall insulators) are among good examples of novel quantum materials. While these novel materials are insulators in the bulk, their edges harbor spinpolarized gapless states with Dirac-fermion-like linear energy-momentum dispersions. If a single Diracfermion edge mode is well separated from bulk states, then it can support dissipationless edge currents since the only available scattering channel (backscattering) is forbidden due to symmetry constraints. Therefore, identifying freestanding and substrate-supported 2D-TIs is highly desirable for low-energyconsuming spintronics applications. We have worked on searching new 2D-TIs and studied their transport and optical properties. In additional to quantum spin Hall effect materials, new classes of topological phases are derived. This TG will also study the 2D quantum anomalous effect, 2D topological crystalline insulators but not limited to what we have mentioned. Furthermore, 2D thin films derived from threedimensional (3D) topological insulators have been proven to possess topological surface or interface states if proper doping of impurities or contact with layers of heterogeneous atoms are arranged. Recently, more classes of 2D materials have been introduce and they exhibit numerous topological phases. This TG will also study the effect of thin films made of topological insulators. Moreover, the high-throughput search method has been applied to different purposes such as 2D and 3D topological materials, transport materials, high entropy alloys and etc..
  • Three dimensional topological materials:
  • (Hsin Lin 林新, T.-R. Chang 張泰榕and Horng-Tay Jeng 鄭弘泰)
  • 3D topological insulators (TI), semimetals (TSM), and topological superconductors (TSC) have received tremendous worldwide attentions in recent years because of their novel physical properties and potential applications in dissipationless spintronics and quantum computing. As such, we have undertaken comprehensive studies on the electronic structures of these novel materials including Cd3As2, TaAs, PbTaSe2, VS2, Phosporene, and so on. We have also studied the heterostructures composed of these materials such as Ag/Bi2Se3, Bi2Se2/MoTe2, and so on. The preliminary results show interesting physical phenomena and great potential spintronics.
  • Advanced two dimensional materials:
  • (C.-K. Yang, T. C. Leung, F.-C. Chuang, Hsin Lin, C.-C. Kaun, S.-H. Lin, T.-R. Chang, and H.-T. Jeng)
  • Thin films and two-dimensional materials are one of the most important research topics in condensed matter physics. Graphene and graphene-based composites possess peculiar physical properties that are important in fundamental physics and promise a wide variety of applications. 2D materials such as honeycomb like materials (other group IV, V and III-V elements) and transition metal dichalcogenides (TMD), as well as metal thin films (MTF) have also drawn intensive attention recently because of the intriguing 2D lattice and electronic structures that both show high industrial potentials. It is the goal of the research proposal to investigate graphene composites, including patterned hydrogenated graphene and other heterogeneous systems, 2D transition metal dichalcogenides such as MoS2, MoTe2, WTe2, and WSe2, and to understand how tailoring and stacking of the 2D layers would produce new physical properties. Surface and interface states of films can be manipulated by doping and contacting with heterogeneous atoms (adsorptions) or by exerting strains. Once electronic band structures of the materials are calculated, transport, optics, and magnetism can in turn be derived. The results can be applied to nanoelectronics, spintronics, and quantum spin-Hall effect. Members of the research team can contribute their learning to the next generation high-tech industry.

IV. Activities:

  • In order to promote collaborative research, we plan to have regular meetings for this thematic group with invitation of some interested researchers in Taiwan to anticipate the discussion. Furthermore, since we are representatives of the first-principles calculations (computational materials research) community in Taiwan, we also have two nationwide workshops to create more opportunity for new research collaborations with invitations of foreign speakers. We are also the representatives of Taiwan to the world’s first-principles communities. In addition, we will engage mutual visits of our members/ participates/collaborators locally and internationally.
  • (A) Regular meetings
  • Monthly or Bi-monthly meeting during semester: we plan to have regular monthly or bi-month meetings for the collaborative research projects and discuss new result/ discoveries, in order to strengthen the collaboration between core members of this TG. Regular meeting for discussions and tracking research achievements by supporting members’ domestic travel expenses.
  • (B). Mini-schools (one-day), workshops, or summer/winter schools
  • We constantly radar globally to identify few world-renowned scholars whose research is strongly related to the missions of this TG and then invited them to deliver a one-day mini-school on his/her research and techniques in greater details.
  • However, the mini-school/school might be delivered by our international collaborators or by our own core members under some circumstances. The topics of schools range from basic use of first-principles calculation package (VASP) and advanced focus topics of topological materials and two-dimensional materials.
  • (C) International workshops (Semi-annual nation-wide workshop)
  • In order to provide opportunities for domestic researchers to exchange expertise and collaborate, and also to train our students, we organize at least one nation wide workshops per year in summer 2019 and in winter 2020 due to budget and operations of NCTS with some leading international scientists as main lecturers. We will encourage our community to attend the annual meeting of Physical Society of Taiwan in winter. A list of past nationwide meeting for first-principles calculation community is listed below. The name of workshop may be different over the years, but the spirit is similar. The workshops would provide members presenting their research achievement, inspiring new ideas, and forming new collaborations. In these two nationwide workshops, we will promote and try to initiate more collaborative research on the target of this TG in Taiwan. The gatherings of this kind have provided an essential channel for fruitful discussions among members of the community; and in particular, have benefited our post-graduate students and young postdoctoral researchers tremendously. We expect influx of new manpower into this TG.
    • 1. 16th Workshop on First-Principles Computational Materials Physics, June 25-26, 2018
    • 2. 15th Workshop on First-Principles Computational Materials Physics, June 26-28, 2017
    • 3. 2016 Summer Workshop on New Quantum Materials and Transport, June 23rd-24th, 2016
    • 4. 2016 Joint Workshop Winter Workshop on of New Quantum Materials, Transport, and Excited States, Jan. 8-20, 2016
    • 5. 2015 Workshop on New Quantum Materials and Transport, July 30-31, 2015
    • 6. 14th Workshop on First-Principles Computational Materials Physics, Jan. 18-20, 2015
    • 7. CMRFG Summer Meeting, July 11~12, 2014
    • 8. 13th Workshop on First-Principles Computational Materials Physics, Feb. 7-9, 2014
  • (D) International Travel fund.
  • We will support young researchers, and graduate students to attend any international conference, school or workshop which is related to our research proposal. One of the regular regional/international workshops is The Asian Workshop on First-Principles Electronic Structure Calculations. This workshop is an annual event rotating among Taiwan, Japan, Korea and China. The most recent workshop, the 21th Asian Workshop was held in Korea and 22nd Asian Workshop will be in Osaka University, Japan. Our community will then organize the 23rd Asian Workshop in Taiwan. The previous workshop in Taiwan was the 19th Asian Workshop, which was held in NCTU, in Hsinchu, Taiwan, Oct. 31 to Nov. 2, 2016. Thus, in the next two years (2019-2020), we will support junior members (assistant professors, postdocs, and graduate students) to attend the 22nd Asian workshops which will be held in Japan (Nov. 2019), in order to involve actively in this Asian community of ab initio research. In addition to the international workshops and conferences, we will also send young participants to visit foreign institutes (USA, Germany, Japan, Singapore, and China) to conduct the research and experience the international environment.
  • (E) Invitation of international visitors to Taiwan
  • In addition to outbound, we will invite and support our overseas/international collaborators to conduct collaborative research in Taiwan. The international collaborators will visit the core members. During their visit, we will arrange a mini school to train our junior participants.


V. Expected achievements:

  • The research topics of this TG include two of the fast growing research fields which are being tackled by many physicists, chemists, materials and life scientists worldwide. The track records of our core members and young participants have consistently shown their capabilities of publishing high-quality and highimpact research papers. The core members in this TG are not only the locally but also internationally recognized pioneers in the field of topological materials. We will continue to pursue and maintain the leadership in this field. Meanwhile, our core members also actively serve local academic and research communities to promote the local researches based on first-principles calculations. Our core members will continuously increase Taiwan’s international visibility by publishing frontier research papers. We expect that some high quality publications will be delivered every year and the research work will be jointly published by the core members, domestic, and international collaborators.

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