In 1937, Italian theoretical physicist Ettore Majorana published a paper, in which he made a brilliant discovery by decomposing Dirac equation into the real and imaginary parts. That is the famous equation describing the motion of a Majorana fermion whose antiparticle is itself. Over the past 81 years, the search of Majorana fermion has been one of the most attractive research topics in physics. In high-energy physics,neutrinos have been proposed as Majorana fermions,and a definite experimental evidence will be one of the biggest discoveries since the discovery of Higgs boson.

(1)完善公平竞争机制。在人才管理体制上，地方国有平台公司组织不能够以单一的政绩作为考量依据，而应该站在社会经济发展、国家战略发展需求指导上，利用竞争机制、建立业绩型、能力型的人才管理体制，建立培养方向、人才选拔多样化的机制，淡化平台公司岗位的权利意识，强化责任和目标，对员工开展问责制管理模式，让管理、业务能力较强的人承担更多的责任、更大的职能，并且以职责为中心、以能力为基础，

In the past twenty years, there were plenty of exciting theoretical proposals and experimental discoveries in condensed matter physics. If one can regard the elementary particles as specific excitations of the quantum ground state of the universe, then quasiparticles in a solid material obeying the same motion equation can be regarded as the duality of elementary particle in a high-order field (the space group of crystal).Searching for exotic fermion excitations in solid state has been a focused topic during the last few years.Beside those dualities of elementary particles, i.e. Dirac fermion (Na3Bi), Weyl fermion (TaAs), condensed matter physicists discovered more exotic excitations which are protected by the crystal symmetry that is higher than the symmetry of universe, i.e., hourglass fermion (KHgSb),three-component fermion (MoP). Nowadays, despite extensive knowledge accumulated on the fermionic excitations in solid state, the appearance of Majorana fermion or bound state in topological superconductors has not been settled conclusively.

Band structure and vortex cores of FeTe0.55Se0.45 (Image by courtesy of GAO Hongjun & DING Hong's groups)

A Majorana fermion is charge neutrality due to the self-conjugation of Majorana operator. It inspired condensed matter physicist to compose Majorana quasiparticles in a topological superconductor, as the Bogoliubov excitation is a mixture of particle and hole components. In the early 2000s, theorists made an initial prediction, that the chiral p-wave superconductor without time-reversal symmetry can harbor Majorana excitations,both the Majorana bound states (0D) inside the halfflux vortex core and the Majorana chiral modes (1D)propagating along the edges of a superconductor. What is more interesting is that Majorana bound states obey the non-Abelian statistics. It has been proved that Majorana bound states can stay at different degenerate ground states by braiding operations. This is the building block of topological quantum qubit and a promising method realizing topological quantum computing.

总之，一定要从学生的实际情况出发，注重学生良好学习习惯的培养，坚持循序渐进的教学原则，方能顺利的完成高一物理教学任务。

However, a p-wave superconductor is rare and extremely sensitive to disorders. It leads to huge difficulties in experimental realization of Majorana fermion. A breakthrough occurred in 2008 when theoretical physicist Liang Fu and Charles L. Kane from University of Pennsylvania proposed a new mechanism based on superconductivity of topological surface state induced by the proximity effect of an ordinary s-wave superconductor. They found Majorana bound state should exist inside the vortex core. This proposal eliminates the difficulties of a p-wave superconductor and creates huge enthusiasm of condensed matter community to study related routes of creating detectable Majorana fermions. Later on, several evidences on Majorana quasiparticles were published on different platforms,i.e., semiconducting nanowire based heterostructure(Delft/Copenhagen), magnetic atomic chain based heterostructure (Princeton), and topological insulator thin films based heterostructure (Shanghai Jiao Tong).However, all those platforms suffer the problem of complex interface.

There are several advantages in the new discovery as comparing with previous observations. They clearly observed the spatial non-split feature of an MBS with its width being nearly energy resolution limited. The MBS is robust against changing tunneling barriers, and it can be observed across a large range of magnetic fields. Comparing to theoretical models, they concluded that the MBS observed come from the quasiparticles of the superconducting topological surface state, while the temperature behavior indicates the bulk thermal quasiparticles could poison the MBS.

Energetic and spatial profile of ZBPs (Image by courtesy of GAO Hongjun & DING Hong's groups)

通过相关智能基础设施的安装，实现轨道实时信息的反馈与管理。这些信息实时的反馈到铁路管理部门以及列车的驾驶人员，对于可能存在的风险与故障可实现有效的规避。这相比于传统的铁路检查工作而言，不仅准确性更高，同时效率优势也十分显著。

The experiments were benefited very much by the excellent facilities and rich experiences of measurement of GAO's group. Team members dedicate themselves to the experiments. In the first 6 months of the experiment,the team worked nearly 24 hours a day and 7 days a week. Some major members of the team even worked continuously for over 30 hours. ZHU Shiyu, WANG Dongfei, FAN Peng, and others even sacrificed their Chinese New Year holidays to continue the experiments.It would not have been possible without all of these to get a large amount of data in a short time.

Since April 2017, Prof. DING Hong has made a close collaboration with Prof. GAO Hongjun at IOP.They guided PhD students WANG Dongfei, KONG Lingyuan, FAN Peng, ZHU Shiyu and other students at IOP to perform measurements of vortex core of FeTe0.55Se0.45 single crystals. During the last year, they measured many samples and carried out He-3 low temperature measurements for more than 100 times using two low-temperature STMs developed at GAO's lab.They successfully obtained repeatable observations of a strong zero-bias peak inside a vortex core of FeTe0.55Se0.45,regarded as a hallmark of an MBS.

In 2015, an ARPES group at the Institute of Physics(IOP), led by Prof. DING Hong, obtained initial evidence of a Dirac-cone-like surface state in a highly correlated Fe-based superconductor FeTe0.55Se0.45 (P. Zhang et al.,APL 105, 172601 (2014)) They then collaborated with a first-principle group at IOP, led by Profs. FANG Zhong and DAI Xi, and proved theoretically and experimentally that there is a topological nontrivial band inversion in this material upon Te substitution (Z.-J. Wang et al., Phys.Rev. B 92, 115119 (2015)). At the same time, another theoretical group of IOP, led by Prof. HU Jiangping,found that Fe(Te,Se) monolayer fi lm may also have the similar topological band inversion by Te substitution(X.-X. Wu et al., Phys. Rev. B 93, 115129 (2016)). This prediction was later verified by DING Hong's group (X.Shiet al., Sci. Bull. 62, 503 (2017)). In 2016 a theoretical group at Stanford University, led by Prof. Shoucheng Zhang, made a theoretical prediction that a Majorana bound state (MBS) may exist inside a vortex core of FeTe0.5Se0.5 under a suitable condition. In 2017, DING Hong's group collaborated with Prof. Shik Shin's group in Tokyo University, and performed ultra-high resolution ARPES experiments on FeTe0.55Se0.45, and for the first time they clearly observed a superconducting topological surface state (P. Zhang et al., Science 360, 182 (2018)).It was found the Fermienergy (EF) is comparable to the superconducting gap (Δ) of the surface state. That proved the combination mentioned above does occur in FeTe0.55Se0.45, and one would naturally expect an MBS inside a vortex core of FeTe0.55Se0.45 can be free from contamination of other trivial bound states.

Temperature and tunneling barrier evolution of ZBPs. (Image by courtesy of GAO Hongjun & DING Hong's groups)

Moreover, their ultra-low critical temperature and very small superconducting gap led to more troubles.The signals of the zero-bias peak (evidence of a Majorana bound state) were always mixed by trivial states that located very near the zero energy as well.It weakens the reliability of experimental evidences and limits potential applications in the future. If one can make a combination of band topological property,intrinsic high temperature superconductivity and strong electron correlations into a single material, the next breakthrough may occur in this field.

All the evidence has led to the conclusion that the observed MBS is largely pure and free of mixing with other trivial bound states. This marks the first clear observation of a pure Majorana bound state. The relatively high temperature indicates that the Majorana bound states can be realized under the He-4 temperature.

相对本科院校而言，大多数高职院校的国际交流机会少一些，外籍教师少，“走进来”的外籍学生少，本土的高职师生“走出去”的机会也少，这种环境使教师和学生失去了直接接触异域文化和体验跨文化交际的机会，跨文化教学也往往流于形式和纸上谈兵，难以收获实质的效果，继而影响了国际合作办学的进一步发展。

This work is published in Science on August 16,2018. The co-first authors are WANG Dongfei, KONG Lingyuan and FAN Pen. The co-corresponding authors are Profs. GAO Hongjun and DING Hong. Prof. Genda Gu at Brookhaven National laboratory provided highquality samples, and Prof. Liang Fu at MIT provided theoretical modeling.

The work at IOP is supported by grants from the Ministry of Science and Technology of China(2013CBA01600, 2015CB921000, 2015CB921300,2016YFA0202300), the National Natural Science Foundation of China (11234014, 11574371, 61390501),and CAS (XDPB08-1, XDB07000000, XDPB0601).