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Ning Chen thought for a while and said:

"I think we can try adding some atomic-scale impurities first. Impurities of this size are more conducive to guiding the elastic ejection of quasiparticles."

After hearing Ning Chen's words, Qi Wan also nodded and said:

"Yes, atomic-scale impurities are the most suitable, and I think just adding one or a few atoms is enough. So let's screen the available atomic types first, and then try them one by one."

Ning Chen and Qi Wan discussed it for a while, and both felt that adding metal atoms was the most suitable.

Adding metal atoms to the sample can cause chemical adsorption between them, thereby changing the electronic structure of the sample.

In this way, the signal of the scanning tunneling microscope can be affected, thereby narrowing the energy gap and generating new electronic states.

…

In the following days, Ning Chen and Qi Wan tried to add various metal atoms as impurities to the sample and observed the changes in the information received by the scanning tunneling microscope after the impurities were added.

As Ning Chen predicted before, after adding impurities to the sample, the STM imaging did have some changes compared to before.

In these images, standing wave images appear similar to ripples in water.

Of course, a lot of the image information does not have great utilization value. Ning Chen and Qi Wan are also constantly changing the types of impurities, striving to find the most suitable impurities to add.

The workload of the entire experiment is still very large, because each measurement requires a long period of debugging, and the addition of atoms requires low-temperature deposition, which is not very easy to operate.

However, after days of experiments, Ning Chen and Qi Wan finally found the most suitable impurity to add.

They found that when a small amount of Ag atoms were added to the sample Bi2Te3, the sample could exhibit a structure similar to a trimer.

This is very helpful for observing electron standing waves in the surface states of topological insulators.

The next time Ren Mingshan came to the laboratory to check the progress of the experiment, Qi Wan told Ren Mingshan about their latest experimental methods and the progress of the experimental subjects during this period.

After learning about the latest experimental progress, Ren Mingshan nodded and said:

"Yes, this method of adding impurities to the sample is very clever. It can replace the impurity atoms with the sample atoms, thereby causing the electron interference effect. In this way, clear electron interference fringes can be produced."

This time, Ren Mingshan did not criticize Qi Wan like last time. After all, at this stage, there was really nothing to criticize about the experimental work done by Qi Wan.

Qi Wan was not happy because of Ren Mingshan's praise. After all, this method was proposed by Ning Chen.

As long as Ren Mingshan didn't criticize himself, Qi Wan felt that he had escaped.

At this time, Ren Mingshan suddenly thought of something and asked Qi Wan and Ning Chen:

"Who came up with the idea of ​​adding impurity atoms to samples?"

Hearing Ren Mingshan's question, Ning Chen was not in a hurry to answer.

Qi Wan hesitated briefly and then said:

"Teacher Ren, Ning Chen proposed it."

Qi Wan knew in her heart that if she said this, she might be criticized by Ren Mingshan again, or Qi Wan might be asked to continue learning from Ning Chen.

However, Qi Wan still feels that he should tell the truth. This is the most basic bottom line for Qi Wan as a person.

This time, Ren Mingshan did not criticize Qi Wan for this, but only said approvingly to Ning Chen:

"As expected of a student who can publish so many articles in Nature at such a young age, his scientific research ability is really strong."

Ning Chen is not a physics major, but he has made such great progress in less than a month after entering the laboratory. Ren Mingshan can only express his admiration for this.

"Teacher Ren deserves the award. Many of the ideas were proposed by Qi Wan. I just helped Qi Wan with some auxiliary work."

Naturally, Ning Chen couldn't overestimate his contribution. Of course, his recognition of Qi Wan was sincere.

"Well, Qi Wan did a good job this time. You two performed very well."

Seeing what Ren Mingshan said, Qi Wan finally found some psychological balance.

After understanding the progress of this topic, Ren Mingshan did not leave immediately.

"By the way, let me tell you two something. I plan to apply for a project recently, which is to study the relationship between topological superconductors and Majorana fermions. Once the previous project is completed, we will almost be able to start a new project. .”

Qi Wan and Ning Chen were both very interested when they heard about the new topic.

Although Qi Wan doesn't like Ren Mingshan criticizing herself, this will not change Qi Wan's love for physics.

Qi Wan also knew in her heart that Ren Mingshan was strict with herself for her own good, but sometimes, Qi Wan needed some time to calm down her mood.

Ning Chen had already prepared to study Majorana fermions, but Ning Chen did not expect that Ren Mingshan did not choose iron-based superconductors as the research object, but chose topological superconductors.

Before Ning Chen asked, Ren Mingshan gave his reasons.

"Ning Chen, your previous small paper on iron-based superconductors and Majorana fermions is actually of great research significance. However, I am not good at iron-based superconductors, and topological superconductors are easier to study. Observation, so I decided it would be better to study this direction."

After listening to Ren Mingshan's explanation, Ning Chen also felt that this reason was very reasonable.

Although the theory in his previous small paper was very complete, if Ning Chen really wanted to explore it through experiments, he would probably not get any results.

Due to its own characteristics, topological superconductors will form a special state, that is, a topological phase, at low temperatures.

In such a state, the number of states that electrons can present on the Fermi surface is much more than that of conventional superconductors, and it is easier to observe various valuable phenomena.

Ren Mingshan explained his general idea to Ning Chen and Qi Wan. After listening to it, Ning Chen and Qi Wan both felt that the whole plan was very feasible.

"Ning Chen, I have to thank you for your previous small paper on iron-based superconductivity and Majorana fermions, which gave me a lot of important inspiration. I didn't expect that teachers can also learn a lot by assigning homework to students. thing."

Ren Mingshan's words carried so much weight that Ning Chen didn't know how to answer them, so he had to keep a polite smile.

After Ren Mingshan left, Qi Wan quickly asked Ning Chen:

"What is that little paper that Teacher Ren is talking about?"

When Ren Mingshan said this just now, Qi Wan was very curious about it.

However, Qi Wan did not dare to ask more questions when Ren Mingshan was present, so she had to wait until Ren Mingshan left to ask Ning Chen.

"Oh, during my previous teacher's quantum physics class, Teacher Ren once left an assignment asking to discuss whether Majorana fermions exist, and then I wrote a short paper and submitted it..."

After listening to Ning Chen's explanation, Qi Wan finally understood the cause and effect.

"I see. No wonder Teacher Ren invited you into the laboratory. I thought it was arranged by the school before."

"Well, originally Yan University would also arrange for me to enter the laboratory, but Teacher Ren gave me a chance in advance, so I came here."

Thinking about it this way, Ning Chen completely relied on his own strength to attract Ren Mingshan's attention.

Qi Wan suddenly felt that it was very stupid for her to secretly compete with Ning Chen.

Ning Chen is obviously someone who has published several papers in "Nature" and has already made achievements in the field of scientific research.

Even though physics is not Ning Chen's strong point, there are still many similarities between physics and materials science.

And Qi Wan is just a rookie who has just been in the laboratory for a few months and has nothing to show off at all.

Seeing that Qi Wan's expression seemed a little lonely, Ning Chen felt that Qi Wan might still have some opinions about Ren Mingshan, so he persuaded:

"Qi Wan, actually I can see that Teacher Ren attaches great importance to you. Maybe he has very high expectations for you, so he is so strict with you."

Normally, at Qi Wan's age, she would only be a freshman or sophomore in college, but Qi Wan had already completed her undergraduate studies and directly entered the doctoral stage.

Even compared to Lin You and Song Xiyun, Qi Wan has higher talent.

"Well, I understand this in my heart. Okay, let's not say so much. Let's finish this topic quickly, and then prepare for a new topic."