"Xu Mang?"

"What's going on here?"

"Don't you and I remember that you were studying axions?"

Surprise was followed by endless confusion. Fan Zhilong asked curiously: "Why are we suddenly studying Weyl semimetals? And this Weyl semimetal is not simpler than your axion. This theory was proposed more than 80 years ago.

.”

Faced with this situation,

Xu Mang just smiled indifferently and said silently: "Actually, I discovered that Weyl fermions may be related to axions. I want to prove Weyl fermions first, and then search for axions based on the existence of Weyl fermions.

"

"you"

"You have to overcome three problems at once." Fan Zhilong said helplessly: "From condensed matter to high-energy particles, you have almost created three miracles."

"It's okay."

"But who knows." Xu Mang said with a smile: "They are all illusory things. It is so difficult to find them. However, Weyl Fermi and Weyl semimetals have relevant theoretical support, and axions are

But it’s just a prediction.”

"Right"

"Professor Fan, do you think the physical properties of the Weyl semimetal I speculated are consistent with its Weyl fermion state?" Xu Mang asked.

Fan Zhilong shook his head and said seriously: "Give me half an hour, I need to take a good look at the content. I just took a look."

"Um!"

"Let me have breakfast by the way." Xu Mang smiled and took out a ball of rice, then sat in the corner and started eating. His ball of rice was relatively simple, with only a fried dough stick in it, and then sprinkled it.

A little salt.

However, the simpler the food, the more delicious it tasted. Xu Mang could almost feel the absolute balance between the glutinous rice and the fried dough sticks.

at this time,

Professor Fan Zhilong began to flip through this manuscript. The first part was normal. It was a solution derived from the Dirac equation. According to quantum theory, Weyl fermions are not fundamental particles.

To be precise, Weyl fermions exist in the form of quasiparticle excitations in condensed matter physics.

Immediately afterwards,

Professor Fan saw a magical transformation. From the existence of the Weyl fermion state, he speculated on the possible physical phenomena of the Weyl semimetal. According to the three characteristics given by Xu Mang, Weyl cone, Fermi arc and

The abnormal chirality made Fan Zhilong vaguely think of a kind of material.

He had encountered this kind of material before, but it was abandoned because it was too strange and too difficult to research.

"Xu Mang?"

"I know that there is a material that is quite consistent with the physical phenomenon you predicted." Fan Zhilong said seriously: "In the past, when I was studying the Dirac electronic state of topological semimetals, based on the Dirac semimetal material theory, I

An idea came up."

Xu Mang was stunned for a moment and looked at him with surprise.

"At that time, I was thinking about what kind of metal it would be if a topological semimetal released the spin degeneracy on its Dirac cone and split it into a chiral Weyl cone?" Fan Zhilong said: "At that time,

I don’t know what material this is yet, but after reading your speculation about Weyl semimetal, I found that it may be Weyl semimetal!”

Damn it!

This seems to be the case!

By analyzing the tips given by Fan Zhilong, Xu Mang discovered that as long as the topological semimetal is changed, the so-called Weyl semimetal can appear.

"Holy shit!"

"Professor Fan, you are awesome!" Xu Mang said with a smile: "What kind of material is it?"

"have no idea."

"I mean changing the structure according to the topological semimetal, and I don't know what material it will be after the change." Fan Zhilong said helplessly: "This kind of breaking the inversion symmetry of time or space to realize the Weyl semimetal has a lot of problems.

difficulty."

indeed,

It’s not easy!

According to Xu Mang's rough guess at the scene, Fan Zhilong's bold guess is that the time reversal symmetry is destroyed by introducing magnetic atoms, or the Weyl electronic state is achieved by continuously doping the components and energy band structure.

but

The magnetic domains brought by magnetic atoms in the system and the destruction of translational symmetry by the atoms will hinder the intrinsic properties of Weyl fermions.

How to realize the Weyl electronic state by breaking the spatial inversion symmetry without requiring detailed and complicated control such as doping is the most critical factor at present.

""

""

The two of them looked at each other with big eyes and small eyes. The current situation was really embarrassing.

This problem seems to have no solution!

"Xu Mang"

"The help I can provide can only go so far, the rest is up to you." Fan Zhilong said: "The Weyl semi-metal material system is a very popular research in condensed matter physics, and many people are involved in it.

in."

Xu Mang nodded. The Weyl fermion state is most likely to appear in condensed matter.

pity

How difficult this is.

Leaving the laboratory,

Xu Mang took his time and came to the computer building. He used the materials science database and made a series of selections based on three inferred materials. However, the answer he got was no. This was another serious blow to Xu Mang.

what to do?

Back to the apartment,

Faced with this problem, Xu Mang conducted a systematic exploration, and finally felt that it was still necessary to do it through principle calculations. From the principle calculations, we can find materials that meet the properties. Whether it can be realized will be discussed later.

"Old Hua!"

"Do you know what Xu Mang is doing recently?" Fan Zhilong found Mr. Hua and said seriously: "He switched from your particle physics to condensed matter physics."

"What?"

"He doesn't study axions anymore?" Hua Yanfeng asked with a confused look on his face: "What's going on? Does Xu Mang think it's impossible to find axions?"

Fan Zhilong shook his head and said seriously: "It's not that. On the contrary, this is the only way to find the axion."

Hua Yanfeng asked hurriedly: "What exactly is going on?"

"Xu Mang thinks that Weyl fermions may be related to axions, but if you want to prove Weyl fermions, you need to find a Weyl semimetal. I read his manuscript this morning and found that his research on Weyl semimetals is quite detailed.

of."

Although Hua Yanfeng is a professor of particle physics, he also has some knowledge of other aspects, such as the so-called Weyl semimetal.

This is no simpler than axions!

Although there are equations and relative solutions, it is still difficult to implement.

"this"

"I didn't expect that the study of axions would involve so many things." Hua Yanfeng said helplessly: "I guess he is quite busy during this period."

"hehe"

"It's more than just being busy."

"I guess Xu Mang is already in a state of distress." Fan Zhilong said with a bitter smile: "First, we must find the Weyl semimetal, secondly, prove the existence of Weyl fermions, and finally, explore axions based on Weyl fermions."

""

After hearing Fan Zhilong's words, Hua Yanfeng didn't know what to say for a moment. What should he do after all the twists and turns?

This question,

Hua Yanfeng thought about it and decided to find Fang Jun first. It would be best if the physics department could provide Xu Mang with some help. Let him do so many things alone. It is estimated that in less than a year, he will change.

Gotta be stupid.

moment,

Hua Yanfeng found Fang Jun and told the director of the physics department what Xu Mang was currently encountering.

"this question"

"I can only say that there is nothing I can do." Fang Jun shook his head repeatedly: "It's not that the department doesn't want to support Xu Mang, it's just that it has limited capabilities and can't help at all. The research on Weyl semimetals has never been proposed, including the subsequent external research.

Elfermions and axions.”
To be continued...