walk into unscientific

Chapter 834: A historic defense (Part )
"."

In the conference room.

Looking at the title of the paper in front of him, Academician Xue Qikun subconsciously made a somewhat funny move:

He slowly took off his glasses, rubbed his eyes vigorously with his knuckles twice, and then he opened his eyes wide and looked at the paper again.

then
Well, the line of words still hasn't changed:
"Discussion on the mechanism of high-temperature superconductivity".

See this situation.

bang bang bang-

Academician Xue Qikun's heart, which had not even moved when he won the Buckley Prize, suddenly began to beat violently.

In today's era, the concept of superconductivity is not unfamiliar to many people.

In physics, superconductivity is a phenomenon in which the resistance of a material becomes zero when the temperature is below a certain level. The material after the transformation is called a superconductor.

Anyone who has been to high school should know this.

In a circuit, charges in a wire move like runners when driven by voltage, creating an electric current, but their movement is hindered by the resistance of the conductor.

If the circuit is made of a superconductor, the charges can run freely in the circuit and the current will continue to flow.

In a loop made of superconducting lead, the current can be passed for months without showing any signs of weakening.

The superconductivity phenomenon was first discovered by Onnes in 1911. He used liquid helium to cool mercury and found that the resistance of mercury became zero at -268.98°C, thus opening the door to the world of superconductivity.

From a business and technology perspective.

Once superconducting materials can be applied, human technology will usher in a new round of leaps and bounds.

For example, in the field of power transmission, household appliances, and transportation - at that time, the wheels of all moving objects can be removed.

At that time, the Formula One Championship will be replaced by the low-altitude hover car race in "Star Wars", and you can drive a hover car and a hover boat to reach every corner of the world.
But unfortunately, ideals are full and reality is very skinny.

Up to now, the practical applications of superconductors are mainly concentrated in specific scenarios such as particle accelerators, magnetic levitation, and superconducting quantum interferometers.

In the field of power engineering, especially the highly anticipated long-distance power transmission by superconducting wires, large-scale application is still a long way off.

What limits the wide-scale application of superconductors?

There is only one root cause:
temperature.

The temperature at which a material turns into a superconductor is called the superconducting critical temperature (Tc). Only below this Tc can the superconductor maintain its superconducting properties.

However, the Tc of most materials is very low, basically below -220°C, and requires the use of liquid nitrogen or liquid helium to maintain a low-temperature environment.

Let's imagine.

You have painstakingly built a superconducting transmission line of several hundred kilometers, and you still need to immerse it in liquid nitrogen for cooling. How ridiculously expensive it is.
Therefore, in order to make superconductors more widely used, it is necessary to find materials with higher Tc and preferably those that can maintain superconducting properties at room temperature (about 25°C).

Since the discovery of superconductivity, physicists have never stopped searching for high-Tc superconductors, but they have always struggled.

In the first 70 years after the discovery of superconductivity, it was difficult to break through the upper limit of Tc even at -240°C.

Fortunately, physicists later discovered superconductors with Tc exceeding -173℃. The current record holder for the highest critical temperature of superconductors is hydrogen sulfide under 150 million atmospheres of pressure, with a Tc of about -73℃, which is still some distance away from the ideal room temperature. Such high-pressure conditions also mean that it is difficult to apply in practice.

at the same time.

Based on the above concepts, superconducting materials have derived two small branches:
Room temperature superconductivity and high temperature superconductivity.

In general.

We call superconductors with a critical temperature above 40K high-temperature superconductors, and superconductors with a critical temperature above about 300K room-temperature superconductors.

That is to say, in the world of superconductivity, "room temperature" is actually much higher than "high temperature".

What's more special is.
Until this day, the physics community still has no consensus on the complete mechanism of high-temperature superconductivity.

This is a black hole in the field of condensed matter physics. Nowadays, there are only two problems in condensed matter physics that are generally recognized as unsolvable:
One is a strongly correlated system, and the other is the complete mechanism of high-temperature superconductivity. (Note: Some people also regard the two as one problem, just like whether cherries and early cherry are the same species. It depends on how you look at it.)
In addition, even the fractional quantum Hall effect, which Academician Xue Qikun specializes in, can only be regarded as a classical problem, not a dead end.

True.

Because this mechanism is infinitely close to the theoretical level, it is actually unlikely to win the Nobel Prize based on it alone. However, for practitioners in the physics field, the significance of unraveling this mechanism is no less than winning the Nobel Prize.

Nowadays, there are many teams at home and abroad engaged in mechanism deduction. Even Academician Xue Qikun has two research groups promoting this topic. The leaders of the project teams are one Changjiang Scholar and the other Young Elite Scholar.

The result was unexpected.

Academician Xue Qikun actually saw such a shocking title at Xu Yun’s master’s defense?
Is Xu Yun deliberately skirting the line and finally playing an ambiguous word game?

Or did he really pick this pearl of condensed matter physics?

"Mr. Zhou, Mr. Zhou!"

Just as Academician Xue Qikun was in shock, a hurried voice suddenly came from a communication device on the desk where Academician Zhou Guangzhao was sitting:
"Mr. Zhou, your heart rate just exceeded 100! Mr. Yang and Mr. Wang's data are also very high!"

"Is there something wrong? Do we need a health care team to come in?"

mentioned earlier.

At this time, among the seven people in the room (including Xu Yun), three were close to or over 95 years old, and the youngest of the three, Zhou Guangzhao, was years old.

Therefore, in order to ensure the safety of several national treasures, the Academy of Sciences set up a medical team in advance to conduct real-time monitoring off-site through equipment worn by several bigwigs.

Just now, the doctor in charge of health care suddenly discovered an abnormality:
The heart rates of several leaders began to rise at the same time. Among them, Academician Zhou Guangzhao's value even jumped from 57 per minute to a peak of 102, which frightened the doctors in the health care team and their heart rates also soared to 180+
"I am fine."

Just as the head of the medical team was wondering whether to rush into the house with the medical kit, Zhou Guangzhao spoke into the communication device:

"I just saw some unexpected content, no need to come in."

"Old Yang and Xiji are fine too. We are both very conscious. If I really feel unwell, I will notify you."

The person on the other end of the communication device was silent for a while, and finally sighed helplessly:

".receive."

As experts who specialize in providing medical care to these senior scientists in the scientific research circle, the members of the medical team naturally know the tempers of these old men.

Although they are usually cheerful, they become very stubborn when it comes to academic matters and cannot be persuaded no matter what.

On the contrary, the retired senior officials in the political circle will cooperate more with the medical team. This is probably the difference between top liberal arts students and science students.
After hanging up the communication device.

Academician Zhou Guangzhao leaned back slightly, took Xu Yun's paper in front of him with both hands, looked at it for a few more times, and then looked up at Xu Yun:
"Student Xu Yun, are you serious about this title?"

Looking at Zhou Guangzhao's slightly scrutinizing gaze, Xu Yun suddenly felt a complicated emotion in his heart.

In the copy, Xu Yun and Zhou Guangzhao could not be said to be friends who would risk their lives for each other, but at least they could be said to be revolutionary comrades who lived together day and night and completed many difficult tasks together. However, in reality, Mr. Zhou had never met himself, and to be frank, his tone even contained a hint of doubt.

Comrades in the copy, strangers in reality.

This is probably what the so-called dislocation of time and space feels like.
However, this emotion was only fleeting in Xu Yun's heart, and he quickly adjusted his state:
"Hello, Academician Zhou. It's an honor for you to attend my graduation defense. I can roughly understand some of your ideas. After all, the level involved in this topic may be relatively high, and it is not something that a master's degree student can touch."

"But on the other hand, from my personal perspective, this master's thesis defense is also an important milestone in my life that cannot be missed. I have no reason to ruin it."

"So, I may be a little arrogant to say that I am quite confident about the quality of the content of this paper."

When Xu Yun spoke, his posture was very humble, but his expression was not too restrained. He answered Zhou Guangzhao's questions in a tactful but firm tone.

After all, it's just as he said.

The paper he wrote was not just a catchy clickbait title, nor was it an ambiguous one. Instead, it clearly explained the complete mechanism of high-temperature superconductivity.

"."

Zhou Guangzhao was silent for a while after hearing this, then turned his head and looked at Xue Qikun, then said to Xu Yun:
"In that case, Xu Yun, you can start your defense."

Xu Yun nodded upon seeing this, and walked from the side of the podium to the center. He quickly glanced at the scene and said:

"Hello, everyone. I am today's respondent, Xu Yun. I am 24 years old, a graduate student, and my student number is 114514."

"My defense topic today is "Exploration of the mechanism of high-temperature superconductivity", a very hot and controversial topic in the field of condensed matter."

Xu Yun paused and pressed the remote control pen. The projector quickly displayed the image of Xu Yun's paper:

"High-temperature superconductivity generally refers to superconductors with a critical temperature of 40K or above, as opposed to low-temperature superconductors such as mercury and lead, which have a critical temperature of around 10K."

"As for applications, it usually refers specifically to copper oxide ceramic superconductors such as YBaCuO and HgBaCaCuO, whose superconducting critical temperature is around 100 K, which is higher than the concept."

"Superconductivity was first discovered by Onnes in 1911. Then, in 44, 1957 years after the discovery of superconductivity, three scientists, Bardeen, Cooper and Schrieffer, proposed the famous BCS theory, which perfectly explained the superconductivity in superconductors such as Hg and Pb. They also won the Nobel Prize in Physics in 1972."

"BCS theory can well explain some properties of low-temperature superconductors, such as energy gap, Meissner effect, and isotope effect. However, many phenomena that violate BCS theory have been found in high-temperature superconductors, such as pseudogap, linear resistance, charge-spin separation, strong superconducting phase fluctuations, etc."

"This suggests the existence of strongly correlated electron systems in high-temperature superconductors that are difficult to treat using perturbation theory or mean field theory."

"So I abandoned the framework of the BCS theory in my paper and adopted another approach to explain high-temperature superconductivity."

Note:
Tomorrow will be the finale, it will be a big chapter, my hands are shaking a little when I write this sentence, the book will be published on November 2021, 11.26, exactly two and a half years, thank you for your company along the way.

(End of this chapter)