报告题目1： Five Challenges of Carbon Nanotubes

报告人：Riichiro Saito (日本东北大学 物理系)

时间： 2023年6月20日(周二) 上午8:30 am - 9:30 am

地点：研究生大厦 109教室

 

报告题目2： Thermoelectric properties of 3D quantum materials

报告人：Nguyen Tuan Hung (日本东北大学)

时间： 2023年6月20日(周二) 上午9:30 am - 10:00 am

地点：研究生大厦 109教室

 

报告题目3： Regulating Valley-polarized transport in graphene with strain and line defect

报告人：Sake Wang (汪萨克) (金陵科技学院)

时间： 2023年6月20日(周二) 上午10:00 am - 10:30 am

地点：研究生大厦 109教室

 

 

　　1. Five Challenges of Carbon Nanotubes
Riichiro Saito

　　Department of Physics,
Tohoku University, Sendai, Japan

In this presentation, we will overview the 30 years history of carbon nanotubes by showing 10 scientific statements on carbon nanotubes and 5 challenges that we should investigate in the near future. My research on carbon nanotubes with many collaborators around the world, especially with Professors Mildred Dresselhaus and Gene Dresselhaus of MIT, has made my 40-years research life as a wonderful one. I hereby express my deepest gratitude to all researchers in the world in the occasion of my retirement from Tohoku University, in March 2023. I sincerely hope that this story will spark the interest of the next young generation of researchers in emerging research of carbon nanotube and new low-dimensional materials.

报告人简介

Riichiro Saito is a Professor at Tohoku University in Japan. He has served as assistant, associated and full professorship at the University of Tokyo, the University of Electrical and Communications and Tohoku University, respectively. He has been a visiting professor at the University of Tokyo, Shanghai University, Zhejiang University and also a visiting scholar at MIT, USA.

As a world-class physicist, professor Saito mainly engages in the study of the physical properties of carbon nanotubes and Raman spectroscopy in two-dimensional material related systems. He has more than 370 papers published in high-impacted journals including PRL, Nat Phys, Nano Lett and 44 books published. His papers have been cited more than 70,000 times, with a single paper cited as many as 11,497 times. Professor Saito has received so many famous awards, including the 18th Leo Esaki Award (2022.3.10), J. Appl Phys Society Paper Award (2017), J Phys Soc. Jpn Paper Award (2014), IUMRS 2009 Somiya Award (2009), Japan Microscope Society Award (2009), Japan Carbon Innovation Research Award (2008), Li Hsun Award of the Chinese Academy of Sciences (2006), and Japan IBM Science Award (physics) (1999).

 

　

　　2. Thermoelectric properties of 3D quantum materials
　Nguyen Tuan Hung ^1,2, Riichiro Saito²

　　¹Frontier Research Institute for Interdisciplinary Science, Tohoku University, Japan
²Department of Physics, Tohoku University, Sendai 980-8578, Japan

Thermoelectric (TE) materials can help to convert waste heat to electricity, which provides an ideal supply for the Internet of things (IoT) sensors. Therefore, finding the TE material with high-performance energy conversion is a fundamental goal in this field. However, it is not easy because of the interdependence of the TE transport parameters (i.e., Seebeck coefficient, electrical conductivity, and thermal conductivity). In order to solve this problem, attempts started for the TE materials in 1993 when Hicks and Dresselhaus presented the quantum con?nement effect [1]. This effect is based on the fact that the density of states has sharp peaks (or so-called van Hove singularity) at the energy edges of the low-dimensional materials [2, 3]. Due to their unique energy band structure, the van Hove singularity can also occur in other quantum materials, such as 3D semimetal materials. Furthermore, the 3D quantum semimetals show many features (high carrier mobility, low thermal conductivity, etc.) that could improve TE properties [4]. In this talk, first, we show enhancement TE performance of 3D Nodal-line semimetal, which has a non-trivial band topology [5]. Second, we will discuss the TE Hall effect of the 3D Dirac and Weyl semimetals under a magnetic field [6].

[1] L. D. Hicks, M. S. Dresselhaus, Phys. Rev. B 47, 12727 (1993); 47, 16631 (1993).

[2] N.T. Hung, E.H. Hasdeo, A.R. T. Nugraha, M.S. Dresselhaus, R. Saito, Phys. Rev. Lett. 117, 036602 (2016).

[3] N. T. Hung, R. Saito, Adv. Quantum Technol. 4, 2000115 (2021).

[4] B. Skinner and L. Fu, Sci. Adv. 4, eaat2621 (2018).

[5] N.T.Hung, A.R.T. Nugraha, J.M. Adhidewata, and R. Saito, Phys.Rev.B 105, 115142 (2022).

[6] P. R. Pratama, R. Saito, and N. T. Hung, Phys. Rev. B (Letter) 106, L081304 (2022).

报告人简介

Nguyen Tuan Hung received a Ph.D. in Physics and Interdepartmental Doctoral Degree Program from Tohoku University in March 2019. Since April 2019, he has been an assistant professor at Frontier Research Institute for Interdisciplinary Sciences (FRIS), Tohoku University. He has been visiting scholars at Institute of Metal Research, Chinese Academy of Sciences (2017) and Massachusetts Institute of Technology (2023). In addition, he got the Aoba Society Prize for the Promotion of Science from Tohoku University (2017), Research Fellowships for Young Scientists from Japan Society for the Promotion of Science (2018), and Prominent Research Fellow from Tohoku University (2021).

　　

3. Regulating Valley-polarized transport in graphene with strain and line defect
Sake Wang (汪萨克)

　　Jinling Institute of Technology, Nanjing, China

　　E-mail address: IsaacWang@jit.edu.cn

In graphene, electrons possess intrinsic degrees of freedom: sublattice pseudospin, spin, and valley [1]. We theoretically investigate the manipulation of valley-polarized currents and the optical-like behaviours of Dirac fermions in graphene with single line defect and/or smoothed strain barrierbyemploying the wave-function matching and the non-equilibrium Green’s function technique.

1) For the smoothed strain barrier [2], we explore the influence of strain on the valley-polarized transmission of graphene.When the transmission is along the armchair direction, we show that the valley polarization andtransmission can be improved by increasing the width of the strained region and increasing(decreasing) the extensional strain in the armchair (zigzag) direction. Furthermore, when we consider thesmooth strain barrier, the valley-polarized transmission can be enhanced by increasing thesmoothness of the strain barrier, as shown in Fig. 1.

2) For single line defect and local uniaxial strain [3], the valley transmission probability increases and the transmission plateau emergesin a large angle range. Such phenomenon originates from resonant tunnelling, and the strain act as anantireflective coating for the valley states, analogous to the antireflective coating in an optical device.This indicates that perfect valley polarization can occur in a larger incident angle range compared withsolely line defect. Interestingly, in the presence of Anderson disorder, even though the transmissiondecreases, the valley polarization is still robust.

We hope that our finding can shed new light on constructinggraphene-based valleytronic and quantum computing devices by solely employing strain.

[1] S. Wang, F. R. Pratama, M. S. Ukhtary, R. Saito, Phys. Rev. B.101, 081414(R) (2020).

[2] S. Wang, H. Tian, M. Sun, J. Phys.: Condens. Matter .35, 304002 (2023).

[3] L. Du, C. D. Ren, L. Cui, W.T. Lu, H.Y. Tian, S.K. Wang, Phys. Scr. 97, 125825 (2022).

报告人简介

　　汪萨克副教授分别于常州大学和东南大学获得凝聚态物理硕士和博士学位，并在日本东北大学作访学。目前就职于江苏金陵学院理学院。获得2D Mater., Semicond Sci Technol等期刊的杰出审稿人。汪教授主要从事低维材料的物理性质和物理化学性质的研究，包括，自旋和能谷电子的输运性质；基于能谷极化的材料光学性质；和使用第一性原理计算设计基于二维材料异质结的新型高效光催化剂。