Chapter 149 Zero-voltage conductivity peak of topological superconductor
Qi Wan is a person who doesn’t know how to hide his emotions. Ning Chen saw Qi Wan’s expression and knew that Qi Wan was probably really relieved about it. .
......
In the following time, Ning Chen and Qi Wan completed all the measurements of the surface states of topological insulators, as well as the analysis and processing of experimental data.
Ning Chen does not plan to participate in the subsequent writing of the paper.
After all, Ning Chen was just here for an internship. Taking this opportunity to quickly accumulate subject experience and break through the bottleneck of materials science was Ning Chen's biggest goal.
As for the results, as long as Ning Chen didn't play a particularly big role in the research process, Ning Chen wouldn't particularly care.
Before starting the new topic, Ning Chen and Qi Wan first studied the theoretical ideas proposed by Ren Mingshan in detail.
Ning Chen must admit that in the field of theoretical physics, Ren Mingshan does have very strong professional abilities.
The theoretical ideas of the entire topic are very detailed. While having a certain degree of novelty, it also provides a variety of experimental plans that can be tried.
What Ning Chen and Qi Wan need to do is to conduct experiments in this general direction and grasp some of the details of the experiments on their own.
Ning Chen feels that perhaps this is the work that a corresponding author really needs to do.
After Ren Mingshan officially completed the application for the project, Ning Chen and Qi Wan started the experiment under the guidance of Ren Mingshan.
"You two must be very familiar with the topological superconductor that we first explored, because you have also studied this kind of material in the previous topic."
As he said that, Ren Mingshan found out the microstructure of this substance on the computer.
Seeing the structure of this material, Qi Wan asked in surprise:
"Teacher Ren, isn't this Bi2Se3?"
This is a topological insulator, which was also their previous topic. One of the substances that has been explored.
Ning Chen was confused at first, but soon understood the reason.
Many topological insulators will show superconductivity at low temperatures after being doped with some metal elements.
There is actually a very close connection between topological insulators and topological superconductors.
Ren Mingshan’s next words were also in line with Ning Chen’s guess.
"You all know that Bi2Se3 is a topological insulator. But if a small amount of copper is added to it, the material will show superconducting electrical properties at a temperature of 3.8K. Next we will What we do is to synthesize this topological superconductor first, and then study its topological superconductivity to see if we can find evidence for the existence of Majorana fermions.”
Ning Chen is in Super. He has very rich research experience in the field of leadership. At this point, even Mingshan cannot compare to Ning Chen.
After confirming the experimental arrangements, everyone officially started research on this topic.
Ning Chen could tell that Ren Mingshan really attached great importance to this project and often participated in it himself. Unlike Qi Wan's previous project, Ren Mingshan would only ask about it every once in a while.
After a phase of work, the project team successfully synthesized this topological superconductor and verified the topological superconductivity of this superconductor.
Of course, these tasks have been done by predecessors and are not the most critical steps in the entire experiment. They are just the prerequisite work for the experiment.
The next data analysis work is the focus of the project.
Ren Mingshan, Ning Chen, Qi Wan and others are looking for traces and evidence of the existence of Majorana fermions in various measurement data.
"Ning Chen, Qi Wan, you guys, look, the zero-voltage conductance peak here may be caused by Majorana fermions."
Ren Mingshan pointed to the zero-voltage point in the point contact spectrum. Each peak of the mountain expresses its own point of view.
In the point contact spectrum of this topological superconductor, almost every spectrum has a large or small conductance peak at zero voltage.
Ning Chen also knows that these may indeed be evidence of the existence of Majorana fermions, but it is only possible.
Because this is not the only possible reason for this phenomenon.
After thinking about it, Ning Chen decided to speak out his thoughts.
"Teacher Ren, I feel that these zero-voltage conductance peaks are not significant enough, and the idea that they are caused by Majorana fermions is not sufficiently convincing. Moreover, these zero-voltage conductance peaks are caused by There is not only one reason for the peak, we need to conduct more detailed experiments to explore this."
Qi Wan was a little surprised that Ning Chen dared to propose that he was different like Ren Mingshan. opinions. If it were Qi Wan, I'm afraid Ning Chen would have to lend him the courage to dare to talk to Ren Mingshan like this.
Hearing Ning Chen’s point of view, Ren Mingshan was not angry, but nodded and said:
"Ning Chen, you are right. We do need to create more significant zero-voltage conductivity peaks. In addition, we also need to exclude in turn whether these zero-voltage conductance peaks are caused by Andreev reflection or heat reflection. , magnetic scattering, non-reflection tunneling and other reasons.”
Ren Mingshan also considered these things just now. After all, it is not that simple to discover the existence of Majorana fermions.
Ren Mingshan's attitude towards Ning Chen is not like treating a student, but more like treating a colleague in the academic field, even though Ning Chen is not older than many of Ren Mingshan's students.
Because in terms of scientific research ability, Ning Chen is already at the level of a university teacher or even a university professor.
……
After completing the initial data analysis, Ren Mingshan, Ning Chen, Qi Wan and others continued to conduct point contact spectrum measurement experiments on topological superconductors.
They hope to measure a more obvious zero voltage peak, and in turn eliminate the influence of other factors on the measurement process.
The experiment went smoothly overall. After the measurement method was improved, these zero voltage peaks did become more obvious.
Many other factors have also been eliminated in turn. From these various signs, it seems that the existence of Majorana fermions may really be verified.
But Ning Chen and Ren Mingshan both know that the experimental phenomena they have made so far are not enough to prove that Majorana fermions cause the superconducting phenomenon of topological superconductors.
Under Ren Mingshan's suggestion, it was decided to measure other types of topological superconductors next.
On this day, Ren Mingshan did not come to the laboratory. While doing experiments, Qi Wan asked Ning Chen:
"Ning Chen, you said we should continue to do this, really Can it produce any different results?"
Ning Chen actually had similar doubts about Qi Wan's question.
At this time, Ning Chen couldn't think of any better way.
Thinking of this, Ning Chen replied:
“Continuing to measure other topological superconductors can enrich our experimental data, so that we can more hope to find evidence of the existence of Majorana fermions.”
Qi Wan heard the meaning of Ning Chen's words and said helplessly:
"That is to say, you don't have any particularly good solution at the moment, right?"
Ning Chen smiled helplessly when he heard this. Even Ren Mingshan had no problem with his thinking, and he certainly couldn't solve it that easily.
While the two continued to conduct experiments, Ning Chen suddenly felt that there were some changes in his brain.
This feeling is like some information fragments in the brain being reorganized.
Ning Chen was no stranger to this feeling, and immediately understood the reason.
"Could it be that... my level of physics has suddenly been upgraded?"
Ning Chen confirmed his suspicion after taking a look at the personal information on the system interface.
Ning Chen has indeed learned a lot in Ren Mingshan's laboratory these days, and his experience in physics is rapidly accumulated every day.
In order to sort out information faster, Ning Chen had to temporarily put down the experiments in his hands and let his brain focus on sorting out information.
"Ning Chen, what's wrong with you?"
Qi Wan saw something was wrong with Ning Chen's state and quickly asked nervously.
“It’s nothing, I just felt a little dizzy suddenly. It should be fine after taking a rest.”
Ning Chen was familiar with this state. It usually only took Ning Chen more than ten minutes to completely consume the benefits brought by the upgrade from Lv1 to Lv2.
Qi Wan didn’t know Ning Chen’s actual situation, but she was still extremely worried, and said anxiously:
“Ning Chen, do you need me to call 120? How about I send it to you? You can go to the school hospital."
Ning Chen felt a little helpless at Qi Wan's nervous look and said quickly:
"No, no, it's probably because I didn't get much rest last night. Why don't you boil some hot water for me to drink first? I feel a little thirsty."
(End of this chapter)