14 3月 2024

18 2月 2022

Highlights

Spontaneous gap opening and potential excitonic states in an ideal Dirac semimetal Ta2Pd3Te5
Peng Zhang#, Yuyang Dong, Dayu Yan, Bei Jiang, Tao Yang, Jun Li, Zhaopeng Guo, Yong Huang, Bo Hao, Qing Li, Yupeng Li, Kifu Kurokawa, Rui Wang, Yuefeng Nie, Makoto Hashimoto, Donghui Lu, Wen-He Jiao, Jie Shen, Tian Qian, Zhijun Wang, Youguo Shi, Takeshi Kondo#
Phys. Rev. X 14, 011047 (2024). https://doi.org/10.1103/PhysRevX.14.011047

Observation and control of the weak topological insulator state in ZrTe5
Peng Zhang#, Ryo Noguchi, Kenta Kuroda, Chun Lin, Kaishu Kawaguchi, Koichiro Yaji, Ayumi Harasawa, Mikk Lippmaa, Simin Nie, Hongming Weng, V. Kandyba, A. Giampietri, A. Barinov, Qiang Li, G.D. Gu, Shik Shin, Takeshi Kondo#
Nature Commun. 12, 406 (2021). https://www.nature.com/articles/s41467-020-20564-8

Multiple topological states in iron-based superconductors
Peng Zhang#, Zhijun Wang, Xianxin Wu, Koichiro Yaji, Yukiaki Ishida, Yoshimitsu Kohama, Guangyang Dai, Yue Sun, Cedric Bareille, Kenta Kuroda, Takeshi Kondo, Kozo Okazaki, Koichi Kindo, Xiancheng Wang, Changqing Jin, Jiangping Hu, Ronny Thomale, Kazuki Sumida, Shilong Wu, Koji Miyamoto, Taichi Okuda, Hong Ding, G.D. Gu, Tsuyoshi Tamegai, Takuto Kawakami, Masatoshi Sato, and Shik Shin#
Nature Phys. 15, 41 (2019). https://www.nature.com/articles/s41567-018-0280-z

Observation of topological superconductivity on the surface of an iron-based superconductor
Peng Zhang#, Koichiro Yaji, Takahiro Hashimoto, Yuichi Ota, Takeshi Kondo, Kozo Okazaki, Zhijun Wang, Jinsheng Wen, G. D. Gu, Hong Ding#, and Shik Shin#
Science 360, 182 (2018). https://science.sciencemag.org/content/360/6385/182

A precise method for visualizing dispersive features in image plots
P. Zhang, P. Richard, T. Qian, Y.-M. Xu, X. Dai, and H. Ding
Rev. Sci. Instrum. 82, 043712 (2011). https://aip.scitation.org/doi/abs/10.1063/1.3585113?journalCode=rsi
The related curvature macro for Igor Pro can be found at Github.

10 12月 2020

Professor

Peng Zhang (张鹏)

Bibliography

2021 – Nanjing University, Professor

2016 – 2021, ISSP, University of Tokyo, Project Researcher

2011 – 2012, Lawerence Berkeley National Laboratory, Visiting Scholar

2009 – 2015, Institute of Physics, Chinese Academy of Sciences, PhD

2005 – 2009, Nanjing University, Bachelor

Address:

C310, Cyrus Tang Building, Department of Physics and National Laboratory of Solid State Microstructures, Nanjing University

Email:

[email protected]

ORCID: 0000-0002-2563-4670

10 12月 2020

课题组的主要方向为高温超导、拓扑超导和拓扑材料的精细电子结构，实验手段主要是高分辨的角分辨光电子能谱。在之前的研究中，我们首次发现了高温铁基超导体中的拓扑超导态，开启了铁基超导体中拓扑超导和马约拉纳准粒子的研究（Science 360, 182 (2018)）。研究组将会建设超高分辨的角分辨光电子能谱仪，同时也会与国内外的角分辨光电子能谱实验室进行合作实验研究，组内学生可以得到国内外交流的机会。

课题组拟每年招收直博生或硕博连读学生1-2名，欢迎有兴趣的同学联系咨询。同时，诚聘博士后或专职研究人员。

Email: [email protected]

10 12月 2020

网站搭建遇到的问题

  1. Docker docker-compose 安装 (ubuntu 18.04)
sudo apt install docker.io

sudo systemctl start docker
sudo systemctl enable docker

sudo apt install docker-compose

安装新版本
sudo curl -L "https://github.com/docker/compose/releases/download/1.27.4/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

sudo chmod +x /usr/local/bin/docker-compose
sudo ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose

卸载
sudo rm /usr/local/bin/docker-compose

2. docker-compose 运行出现问题

sudo usermod -aG docker $USER

3. docker-compose yml 文件

version: '3.3'

services:
  wordpress:
    depends_on: 
      - db
    image: wordpress:latest
    volumes: 
      - ./wordpress_files:/var/www/html
    ports: 
      - "80:80"
    restart: always
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress_db_pw

  db:
    image: mysql:latest
    volumes:  
      - ./mysql_files:/var/lib/mysql
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: db_root_pw
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress_db_pw

volumes:
  wordpress_files:
  db_data:

dokcer-compose 常用命令

docker-compose up -d
docker-compose down --volumes //删除持久数据
docker-compose down

4. ufw 对 docker 不起作用，解决方案

创建文件/etc/docker/daemon.json，并将以下内容放入：
{
    "iptables": false
}
systemctl restart docker

5. Libretto 主题相关

(1) 移除分类title中的“分类”字样

在主题的functions.php中添加如下代码

add_filter( 'get_the_archive_title', function ( $title ) {
    if( is_category() ) {
        $title = single_cat_title( '', false );
    }

    return $title;
});

(2)移除文章显示部分的title区域

额外css中添加

.entry-title {
display: none;
}

.entry-header {
display: none;
}

(3)移除文章中首行和首字母的强调显示

额外css中添加


.format-standard:not(.post-password-required) .entry-content > p:first-of-type:not(.no-emphasis)::first-line, .page:not(.post-password-required) .entry-content > p:first-of-type:not(.no-emphasis)::first-line, .emphasis::first-line {
  font-size: 1.2em;
  font-family: initial;
  font-weight: normal;
  color: #363431;
  letter-spacing: initial
}

.format-standard:not(.post-password-required) .entry-content > p:first-of-type:not(.no-emphasis)::first-letter, .page:not(.post-password-required) .entry-content > p:first-of-type:not(.no-emphasis)::first-letter, .emphasis::first-letter {
  font-size: 1.1em;
  color: #363431;
  font-weight: normal;
  line-height: 2;
  margin: 0;
  float: none;
  letter-spacing: initial;
}

(4)如何将首页定位到 home 分类？

使用了redirection插件

(5)如何修改底部的版权信息？

修改主题里footer.php相应的部分。

(6)修改登录链接，增强安全性

已通过插件实现

9 12月 2020

2011 – 2021

32. Visualization of the strain-induced topological phase transition in a quasi-one-dimensional superconductor TaSe3
Chun Lin, Masayuki Ochi, Ryo Noguchi, Kenta Kuroda, Masahito Sakoda, Atsushi Nomura, Masakatsu Tsubota, Peng Zhang, Cedric Bareille, Kifu Kurokawa, Yosuke Arai, Kaishu Kawaguchi, Hiroaki Tanaka, Koichiro Yaji, Ayumi Harasawa, Makoto Hashimoto, Donghui Lu, Shik Shin, Ryotaro Arita, Satoshi Tanda, Takeshi Kondo
Nature Materials. 20, 1093 (2021). https://doi.org/10.1038/s41563-021-01004-4.

31. Evidence for a higher-order topological insulator in a three-dimensional material built from van der Waals stacking of bismuth-halide chains
Ryo Noguchi, Masaru Kobayashi, Zhanzhi Jiang, Kenta Kuroda, Takanari Takahashi, Zifan Xu, Daehun Lee, Motoaki Hirayama, Masayuki Ochi, Tetsuroh Shirasawa, Peng Zhang,Chun Lin, Cedric Bareille, Shunsuke Sakuragi, Hiroaki Tanaka, So Kunisada, Kifu Kurokawa, Koichiro Yaji, Ayumi Harasawa, Viktor Kandyba, Alessio Giampietri, Alexei Barinov, Timur K. Kim, Cephise Cacho, Makoto Hashimoto, Donghui Lu, Shik Shin, Ryotaro Arita, Keji Lai, Takao Sasagawa and Takeshi Kondo
Nature Materials 20, 473 (2021). https://www.nature.com/articles/s41563-020-00871-7

30. Observation and control of the weak topological insulator state in ZrTe5
Peng Zhang#, Ryo Noguchi, Kenta Kuroda, Chun Lin, Kaishu Kawaguchi, Koichiro Yaji, Ayumi Harasawa, Mikk Lippmaa, Simin Nie, Hongming Weng, V. Kandyba, A. Giampietri, A. Barinov, Qiang Li, G.D. Gu, Shik Shin, Takeshi Kondo#
Nature Commun. 12, 406 (2021). https://www.nature.com/articles/s41467-020-20564-8

29. A new Majorana platform in an Fe-As bilayer superconductor
Wenyao Liu, Lu Cao, Shiyu Zhu, Lingyuan Kong, Guangwei Wang, Michał Papaj, Peng Zhang, Ya-Bin Liu, Hui Chen, Geng Li, Fazhi Yang, Takeshi Kondo, Shixuan Du, Guang-Han Cao, Shik Shin, Liang Fu, Zhiping Yin, Hong-Jun Gao and Hong Ding
Nature Commun. 11, 5688 (2020), https://www.nature.com/articles/s41467-020-19487-1

28. Magnetic topological insulator MnBi6Te10 with a zero-field ferromagnetic state and gapped Dirac surface states
Shangjie Tian, Shunye Gao, Simin Nie, Yuting Qian, Chunsheng Gong, Yang Fu, Hang Li, Wenhui Fan, Peng Zhang, Takesh Kondo, Shik Shin, Johan Adell, Hanna Fedderwitz, Hong Ding, Zhijun Wang, Tian Qian, and Hechang Lei
Phys. Rev. B 102, 035144 (2020), https://journals.aps.org/prb/abstract/10.1103/PhysRevB.102.035144

27. Dirac Surface States in Intrinsic Magnetic Topological Insulators EuSn2As2 andMnBi2nTe3n+1
Hang Li, Shun-Ye Gao, Shao-Feng Duan, Yuan-Feng Xu, Ke-Jia Zhu, Shang-Jie Tian, Jia-Cheng Gao, Wen-Hui Fan, Zhi-Cheng Rao, Jie-Rui Huang, Jia-Jun Li, Da-Yu Yan, Zheng-Tai Liu, Wan-Ling Liu, Yao-Bo Huang, Yu-Liang Li, Yi Liu, Guo-Bin Zhang, Peng Zhang, Takeshi Kondo, Shik Shin, He-Chang Lei, You-Guo Shi, Wen-Tao Zhang, Hong-Ming Weng, Tian Qian, and Hong Ding
Phys. Rev. X 9, 041039 (2019). https://journals.aps.org/prx/abstract/10.1103/PhysRevX.9.041039

26. Multiple topological states in iron-based superconductors
Peng Zhang#, Zhijun Wang, Xianxin Wu, Koichiro Yaji, Yukiaki Ishida, Yoshimitsu Kohama, Guangyang Dai, Yue Sun, Cedric Bareille, Kenta Kuroda, Takeshi Kondo, Kozo Okazaki, Koichi Kindo, Xiancheng Wang, Changqing Jin, Jiangping Hu, Ronny Thomale, Kazuki Sumida, Shilong Wu, Koji Miyamoto, Taichi Okuda, Hong Ding, G.D. Gu, Tsuyoshi Tamegai, Takuto Kawakami, Masatoshi Sato, and Shik Shin#
Nature Phys. 15, 41 (2019). https://www.nature.com/articles/s41567-018-0280-z

25. Disorder-sensitive nodelike small gap in FeSe
Yue Sun, Shunichiro Kittaka, Shota Nakamura, Toshiro Sakakibara, Peng Zhang, Shik Shin, Koki Irie, Takuya Nomoto, Kazushige Machida, Jingting Chen, and Tsuyoshi Tamegai
Phys. Rev. B 98, 064505 (2018). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.064505

24. Observation of topological superconductivity on the surface of an iron-based superconductor
Peng Zhang#, Koichiro Yaji, Takahiro Hashimoto, Yuichi Ota, Takeshi Kondo, Kozo Okazaki, Zhijun Wang, Jinsheng Wen, G. D. Gu, Hong Ding#, and Shik Shin#
Science 360, 182 (2018). https://science.sciencemag.org/content/360/6385/182

23. Experimental evidence of hourglass fermion in the candidate nonsymmorphic topological insulator KHgSb
Junzhang Ma, Changjiang Yi, Baiqing Lv, Zhijun Wang, Simin Nie, Le Wang, Lingyuan Kong, Yaobo Huang, Pierre Richard, Peng Zhang, Koichiro Yaji, Kenta Kuroda, Shik Shin, Hongming Weng, Bogdan Andrei Bernevig, Youguo Shi, Tian Qian, Hong Ding
Sci. Adv. 3, e1602415 (2017). https://advances.sciencemag.org/content/3/5/e1602415

22. Topologically entangled Rashba-split Shockley states on the surface of grey arsenic
Peng Zhang, J.-Z. Ma, Y. Ishida, L.-X. Zhao, Q.-N. Xu, B.-Q. Lv, K. Yaji, G.-F. Chen, H.-M. Weng, X. Dai, Z. Fang, X.-Q. Chen, L. Fu, T. Qian, H. Ding, S. Shin
Phys. Rev. Lett. 118, 046802 (2017), Editor’s suggestion. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.046802

21. Angle-resolved photoemission observation of Mn-pnictide hybridization and negligible band structure renormalization in BaMn2As2 and BaMn2Sb2
W.-L. Zhang, P. Richard, A. van Roekeghem, S.-M. Nie, N. Xu, P. Zhang, H. Miao, S.-F. Wu, J.-X. Yin, B. B. Fu, L.-Y. Kong, T. Qian, Z.-J. Wang, Z. Fang, A. S. Sefat, S. Biermann, and H. Ding
Phys. Rev. B 94, 155155 (2016). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.155155

20. Disentangling the surface and bulk electronic structures of LaOFeAs
P. Zhang, J. Ma, T. Qian, Y. G. Shi, A. V. Fedorov, J. D. Denlinger, X. X. Wu, J. P. Hu, P. Richard, H. Ding
Phys. Rev. B 94, 104517 (2016). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.104517

19. Observation of high-Tc superconductivity in rectangular FeSe/STO(110) monolayer
P. Zhang, X.-L. Peng, T. Qian, P. Richard, X. Shi, J.-Z. Ma, B.-B. Fu, Y.-L. Guo, Z. Q. Han, S. C. Wang, L. L. Wang, Q. -K. Xue, J. P. Hu, Y.-J. Sun, H. Ding
Phys. Rev. B 94, 104510 (2016). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.94.104510

18. Surface State Bands in Superconducting (PtxIr1-x) Te2
Wan-Dong Kong, Hu Miao, Tian Qian, Zhi-Jun Wang, Gang Xu, Ai-Fang Fang, Yao-Bo Huang, Peng Zhang, Xun Shi, Zhong Fang, Xi Dai, Pierre Richard, Nan-Lin Wang, Hong Ding
Chin. Phys. Lett. 32, 077402 (2015). https://iopscience.iop.org/article/10.1088/0256-307X/32/7/077402

17. Observation of a Van Hove singularity and implication for strong-coupling induced Cooper pairing in KFe2As2
Delong Fang, Xun Shi, Zengyi Du, Pierre Richard, Huan Yang, X.X.Wu, Peng Zhang, Tian Qian, Xiaxin Ding, Zhenyu Wang, T. K. Kim, M. Hoesch, Aifeng Wang, Xianhui Chen, Jiangping Hu, Hong Ding and Hai-Hu Wen
Phys. Rev. B 92, 144513 (2015). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.144513

16. Topological nature of FeSe0.5Te0.5 superconductor
Zhijun Wang*, P. Zhang*,Gang Xu, L.K. Zeng, H. Miao, Xiaoyan Xu, T. Qian, Hongming Weng, P. Richard, A. V. Fedorov, H. Ding, Xi Dai, Zhong Fang
Phys. Rev. B 92, 115119 (2015). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.92.115119

15. Observation of two distinct dxz/dyz band splittings in FeSe
P. Zhang, T. Qian, P. Richard, X. P. Wang, H. Miao, B. Q. Lv, B. B. Fu, T. Wolf, C. Meingast, X. X. Wu, Z. Q. Wang, J. P. Hu and H. Ding
Phys. Rev. B 91, 214503 (2015). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.214503

14. Structural phase transition associated with van Hove singularity in 5d transition metal compound IrTe2
T. Qian, H. Miao, Z. J. Wang, X. Liu, X. Shi, Y. B. Huang, P. Zhang, N. Xu, P. Richard, M. Shi, M. H. Upton, J. P. Hill, G. Xu, X. Dai, Z. Fang, H. C. Lei, C. Petrovic, A. F. Fang, N. L. Wang and H. Ding
New J. Phys. 16 123038 (2014). https://iopscience.iop.org/article/10.1088/1367-2630/16/12/123038

13. Evolution from incoherent to coherent electronic states and its implications for superconductivity in FeTe1−xSex
E. Ieki, K. Nakayama, Y. Miyata, T. Sato, H. Miao, N. Xu, X.-P. Wang, P. Zhang, T. Qian, P. Richard, Z.-J. Xu, J. S. Wen, G. D. Gu, H. Q. Luo, H.-H. Wen, H. Ding, and T. Takahashi
Phys. Rev. B 89, 140506(R) (2014). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.140506

12. Angle-resolved photoemission spectroscopy observation of anomalous electronic states in EuFe2As2−xPx
P. Richard, C. Capan, J. Ma, P. Zhang, N. Xu, T. Qian, J. D. Denlinger, G.-F. Chen, A. S. Sefat, Z. Fisk and H. Ding
J. Phys.: Condens. Matter 26, 035702 (2014). https://iopscience.iop.org/article/10.1088/0953-8984/26/3/035702

11. Observation of an electron band above the Fermi level in FeTe0.55Se0.45 from in-situ surface doping
P. Zhang, P. Richard, N. Xu, Y.-M. Xu, J. Ma, T. Qian, A. V. Fedorov, J. D. Denlinger, G. D. Gu, and H. Ding
Appl. Phys. Lett. 105, 172601 (2014). https://aip.scitation.org/doi/10.1063/1.4900870

10. Observation of Momentum-Confined In-Gap Impurity State in Ba0.6K0.4Fe2As2: Evidence for Antiphase s+- Pairing
P. Zhang, P. Richard, T. Qian, X. Shi, J. Ma, L.-K. Zeng, X.-P. Wang, E. Rienks, C.-L. Zhang, Pengcheng Dai, Y.-Z. You, Z.-Y. Weng, X.-X. Wu, J. P. Hu, and H. Ding
Phys. Rev. X 4, 031001 (2014). https://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.031001

9. Electronic Band Structure of BaCo2As2: A Fully Doped Ferropnictide Analog with Reduced Electronic Correlations
N. Xu, P. Richard, A. van Roekeghem, P. Zhang, H. Miao, W.-L. Zhang, T. Qian, M. Ferrero, A. S. Sefat, S. Biermann, and H. Ding
Phys. Rev. X 3, 011006 (2013). https://journals.aps.org/prx/abstract/10.1103/PhysRevX.3.011006

8. Magnetically doped semiconducting topological insulators
X. F. Kou, W. J. Jiang, M. R. Lang, F. X. Xiu, L. He, Y. Wang, Y. Wang, X. X. Yu, A. V. Fedorov, P. Zhang, and K. L. Wang
J. Appl. Phys. 112, 063912 (2012). https://aip.scitation.org/doi/10.1063/1.4754452

7. Weak Anti-localization and Quantum Oscillations of Surface States in Topological Insulator Bi2Se2Te
Lihong Bao, Liang He, Nicholas Meyer, Xufeng Kou, Peng Zhang, Zhi-gang Chen, Alexei V. Fedorov, Jin Zou, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle and Faxian Xiu
Sci Rep. 2, 726 (2012). https://www.nature.com/articles/srep00726

6. Effects of Ru substitution on electron correlations and Fermi-surface dimensionality in Ba(Fe1−xRux)2As2
N. Xu, T. Qian, P. Richard, Y.-B. Shi, X.-P. Wang, P. Zhang, Y.-B. Huang, Y.-M. Xu, H. Miao, G. Xu, G.-F. Xuan, W.-H. Jiao, Z.-A. Xu, G.-H. Cao, and H. Ding
Phys. Rev. B 86, 064505 (2012). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.86.064505

5. Evolution of electronic structure upon Cu doping in the topological insulator Bi2Se3
Y. Tanaka, K. Nakayama, S. Souma, T. Sato, N. Xu, P. Zhang, P. Richard, H. Ding, Y. Suzuki, P. Das, K. Kadowaki, and T. Takahashi
Phys. Rev. B 85, 125111 (2012). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.125111

4. Isotropic superconducting gaps with enhanced pairing on electron Fermi surfaces in FeTe0.55Se0.45
H. Miao, P. Richard, Y. Tanaka, K. Nakayama, T. Qian, K. Umezawa, T. Sato, Y.-M. Xu, Y. B. Shi, N. Xu, X.-P. Wang, P. Zhang, H.-B. Yang, Z.-J. Xu, J. S. Wen, G.-D. Gu, X. Dai, J.-P. Hu, T. Takahashi, and H. Ding
Phys. Rev. B 85, 094506 (2012). https://journals.aps.org/prb/abstract/10.1103/PhysRevB.85.094506

3. Strong nodeless pairing on separate electron Fermi surface sheets in (Tl, K)Fe1.78Se2 probed by ARPES
X.-P. Wang, T. Qian, P. Richard, P. Zhang, J. Dong, H.-D. Wang, C.-H. Dong, M.-H. Fang, H. Ding
Europhysics Letters 93, 57001 (2011). https://iopscience.iop.org/article/10.1209/0295-5075/93/57001

2. Absence of a Holelike Fermi Surface for the Iron-Based K0.8Fe1.7Se2 Superconductor Revealed by Angle-Resolved Photoemission Spectroscopy
T. Qian, X.-P. Wang, W.-C. Jin, P. Zhang, P. Richard, G. Xu, X. Dai, Z. Fang, J.-G. Guo, X.-L. Chen, H. Ding
Phys. Rev. Lett. 106, 187001 (2011). https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.106.187001

1. A precise method for visualizing dispersive features in image plots
P. Zhang, P. Richard, T. Qian, Y.-M. Xu, X. Dai, and H. Ding
Rev. Sci. Instrum. 82, 043712 (2011). https://aip.scitation.org/doi/abs/10.1063/1.3585113?journalCode=rsi
The related curvature macro for Igor Pro can be found at Github.

9 12月 2020

Angle-resolved photoemission spectroscopy

Angle-Resolved Photoelectron Spectroscopy (ARPES) is a useful tool to probe electronic structures of crystals. Based on photoelectric effect, we use a light to kick out the electrons, and measure the angle (k) and energy (E) of outgoing photoelectrons. The photoelectron intensity can be expressed as \(I(k,E) \sim M A(k,E) f(E)\).

Band dispersion is directly contained in the spectral function \(A(k,\omega)\). Thus, any physical problem, that is related to band dispersion, can be studied by ARPES. Some examples are: Topological materials with special band structure; Superconductors: Gap opening in the band dispersion will appear at Fermi level in the superconducting state; Nematic order: Band degeneracy at high symmetry points will be lifted due to the symmetry breaking; Electron-phonon coupling: A kink structure will appear in the band dispersion at the phoono energy; and so on. All these phenomenons are related to the band dispersion, which can be readily studied by ARPES.

ARPES to study band structures

We also need to be aware of the spectral weight in the spectral function \(A(k,E)\). In most cases, we are only interested in the band dispersion, and ignore the spectral weight. However, the spectral weight of a band may not be the same over entire Brillouine zone, which may change the appearance of a band in ARPES. In a superconductor, the band dispersion is particle-hole symmetric. But in the spectral function, only part of the band is shown, since the electron weight is not one for all the states. The impurity state is another example. We expect a non-dispersive band for impurity states as the impurities have no translation symmetry. However, in the spectral function, we find that the impurity states are highly localized in momentum space, and only a small part of the non-dispersive band is occupied. 1

Band dispersion vs Spectral function

The matrix element effect \(M\) is related to many factors such as the symmetries of electron orbitals in solids, the polarization of light, and photon energies. It is usually complicated and cannot be fully understood in most of the cases. However, the ARPES setup generally has mirror symmetries. From the mirror symmetry eigenvalues of \(\psi_f\), \(\mathbf{P}\) and \(\psi_i\) in \(M \sim <\psi_f|\mathbf{A} \cdot \mathbf{P}|\psi_i>\), we can get information on the orbital character of the bands. 2

[1] Zhang et al, Phys. Rev. X 4, 031001 (2014).
[2] See supplement of Science 360, 182 (2018).