You plug the cable into the wall socket and run the device by passing the electric current through the circuits. Sometimes you even run so much that when your bill comes, it feels like the world is destroyed.
In this article, we will examine the superconductors that transmit that great electricity that shapes our lives. We will tightly explain this article with basic questions such as why it transmits very well, where it is used, and how it was found. Fasten your belts because superconductor physics has a 103-year history.
The adventure has begun and the revolution!
Consider yourself. You are one with your hands, eyes, feet, and internal organs. Just like atoms. With their protons, neutrons and electrons, they are a whole. Of course, there are building blocks that also form these particles. For example, electrons are made up of leptons. With this consciousness that nature gives us, we are smart enough to investigate both micro dimensions and macro dimensions.
In fact, the whole story begins with the intellectuals who fought “absolute zero war” in the 20th century. At that time, there were physicists competing with each other to bring the elements to lower temperatures. It has been shown theoretically that the lowest temperature that can be reached is 0 Kelvin (-273 C). If you say why we cannot get even colder, it is because the atoms are now officially freezing at that temperature. It gives.
The discovery was in April 1911. Dutch physicist Heike Onnes and his team were producing mercury resistors for mercury thermomets. At the same time, they manage to liquefy the helium down to -268 C since they enter the race even more. (Absolute zero -273 degrees has never been so close!) Our curious physicist takes the mercury wire he produces, immerses it in the coldest liquid of his time and wonders what will happen. What’s going on? Revolution!
I have to give a brief introduction to the revolution. Let’s just think. You can think of an experiment you did in primary school. Two cables, a light source and a battery! We connect them correctly and turn on the light. In a circuit, you cannot have the electricity you get from your power supply on your circuit without loss. I SHAKING; Even if your battery is 5 Volt Duracell, 2.5 volt electricity will be energized in your instrument due to the resistance in the circuit. The voltage in the circuit is equal to the product of current and resistance. So much so that even the cable you use has resistance and creates loss when carrying electricity in your battery.
We said that everything is made up of atoms and there are electrons inside atoms. The electric current is created by these electrons that orbit around the last orbit of the atoms. Since the cable is made up of atoms, electrons that travel through the cable absolutely hit the atoms of the cable. In fact, what we call resistance are poor electrons that crash on the road. As a result of resistance, your circuit becomes hot. Almost everyone’s laptop warmed his leg. The only reason for this is the electric monster electrons!
Mr. Onnes couldn’t believe his eyes when he immersed this mercury wire in extreme cold liquid Helium and did an experiment! In mercury wire, electricity was moving without any loss! So the resistance suddenly dropped to zero! That is that it was a revolution, zero loss of power could send to Turkey from the United States. This was to open the doors of savings upon saving!
In addition, today we use many devices limited due to heating problems. Such a technology also means making our devices much stronger and full capacity. You could produce more sensitive devices, your computer won’t heat your leg, your bill won’t burn your pocket (I’m not so sure of it), you could have batteries that last longer forever! I hope Mr. Onnes’s sleep patterns have not been disturbed after the discovery.
After this discovery, a great excitement started. Now physicists who would work for this job were required. Especially after the Nobel Prize for Physics, we know that there are a lot of physicists leaping into this field.
But how did suddenly the resistance disappear? In fact, not many physicists imagined such a situation. Of course there were physicists who were hoping to achieve zero resistance, but they thought there would be a gradual decrease. As you can see in the graph, a sudden change had a shock effect. After this experiment, theoretical physicists took over. They had to mathematically model why this was so, and to illuminate the subject, and they did!
Diamagnetic Discovery and A New Definition
One of the major breakthroughs of the adventure was the discovery of the dislike of superconducting materials from the magnetic field. Our explorers W. Meissner and R. Ochsenfeld discovered in 1933 that strangely superconducting materials exclude the magnetic field. This discovery was the observation of the exclusion of the magnetic field of the electric field on the surface of our superconductor.
This exclusion event is known as the Meissner Effect. After the observation, Fritz and Heinz London brothers made the theoretical explanation.
They made connections and developed equations between the magnetic field and the power of superconducting materials to conduct electricity. From this point on, superconducting materials have now begun to be defined as well excluding the magnetic field rather than conducting electricity well. Of course, it is necessary to know a little magnetism to understand this issue. A document in my references2 appeals to the eyes and offers a very good summary, I recommend.
Isotope Effect and BCS Theory
Let’s first define what isotope means. We call atoms with the same number of protons but different numbers of neutrons as isotope atoms. In other words, since the number of neutrons of our isotope atoms is different, their masses are also different. (The mass of a neutron is almost equal to the proton and corresponds to 1836 times the mass of the electron.) Of course, we expect some changes in our superconductor as well. Let’s not forget to give extra information. You may have heard of deuterium, which is the isotope of hydrogen.
The most important reason why the Sun warms us is that hydrogen turns into a deuterium isotope. The reaction of the Sun begins in this way. This first reaction corresponds to 8 percent of the energy emitted by the Sun.
Now we are in the 1950s. Emanuel Maxwell is our new explorer. He examines the different isotopes of mercury and sees that different isotopes require different temperatures to wear their superconductor cape. So we realize that neutrons have a big task on the critical temperature of the cloak.
BCS theory appeared in 1957. The BCS comes from the initials of the surnames of three minds: John Bardeen, N. Cooper, John Schrieffer. Let’s clarify the theory of these gentlemen.
According to the BCS theory, electrons acting in the path of our superconductors allow a different quantum state when they form the Cooper pair.
In the figure, you see two electrons that have created the Cooper pair. As the electron travels on the road, positive ions also approach it. The first electron on the path travels by attracting positive ions on the path. Let’s call the positive ions attracted by the first electron Cavidan. You know electrons, they are very fast. When our first electron leaves the Cavidans, you expect them to go back to their old places, as there is no force to hold the Cavidans there.
Do you think he is next to his mother? Do you think you’re the first? It’s up to you. But this does not happen! Because there is a second electron that forms the Cooper pair that follows the first electron. While the warriors will go back to their old places, the second electron comes and they cannot go.
At the beginning of the article, I said that electricity was created by electrons and that the resistance was electrons that crashed on the road. These electrons that travel in our superconducting material can travel more easily when they form a Cooper pair. It is as if the municipality of the atom has traveled for electrons and can go without any accidents. For example, we can think that the electron in front opens the way and that the back follows it. So how do these electrons move in pairs, how do they communicate? Thanks to phonons! They create mechanical vibration by disrupting the structure of the atomic mesh and can enable electrons to move from atom to atom without accident. They are virtual particles capable of establishing a bond between electrons and enabling their coherent motion.
The creators of the Nobel Prize in Physics awarded in 1972, since the BCS theory was seen as a powerful enough theory to explain how electricity traveled without resistance!
Josephson Joint and SQUID
I’m sorry, but for the second time, I will ask you to imagine the circuit you did in elementary school. You have connected your Duracell battery, which lasts up to 10 times longer than ordinary zinc carbon batteries, with the help of your cables to the light source and illuminated the surroundings. You did this with your cables!
In 1962, Brian Josephson imagined something difficult to establish in primary school. This time we imagine two superconducting sheets. We place thin insulating material between them. Suppose that our superconductors are cables, and our insulating material is a plastic part. Electron flow does not occur if we interrupt the wire between the cables with a flat logic and put a plastic. However, micro-scale observations showed that; The Cooper pair electrons, which are entangled between superconductors, can reach the crossroads through quantum tunneling and create direct current without any connection.
They’re officially jumping across the street, right? Of course, if you have a particle head, it will sound like that. This prediction is proven experimentally a year later. By the way, for those who do not know about quantum tunneling, we have a nice, simple article here.
Now let’s come to SQUID. There was such a sea creature. When I searched it from Google, I saw it and it is a very sweet, cartoon character. But it is our tool that has nothing to do with it.
SQUID: Superconducting Quantum Interference Device: Quantum Interference Device
This device is very important, even if you do not find much in its name. A highly sensitive device for measuring very weak magnetic fields, containing annular superconductors equipped with Josephson joints. It is used in many fields from medicine to geology. In the later parts of the article, while examining the usage areas of superconductors, we will examine this device with a separate heading called SQUID.
First Type and Second Type Superconductors
As we said at the beginning of the article, our first superconductor was in 1911. This superconductor Helium was obtained by cooling. What we call First Type Superconductor are substances that consist of only one metal element. However, Second Type Superconductors consist of two metals. So an alloy3. Some transition metals may also be Second Type Superconductors.
In 1931, Russian physicist Lev Shubnikov is our Second Type Superconductors explorer. (No, they did not give Nobel to this man.) As you know, First Type Superconductors were excluding the magnetic field thanks to the Meissner effect. But there is a limit in magnetic field, right? For example, a holiday village we go every summer and a tree there. A year later, if you gain a lot of weight and sit on the branch of the poor tree that always carries you, it will break. The same logic applies to superconductors. It excludes the magnetic field but has a limit. We call it a critical magnetic field. If you apply a massive magnetic field in Hurra, superconductivity will be impaired.
The situation is a bit complicated in second type superconductors. They exclude, exclude, and confuse. Yes, let’s clarify this rhyme I wrote. There are two critical values in our Second Type Superconductor material. The first is called the lower critical magnetic field, and the second is called the upper critical magnetic field.
If we apply magnetic field to our Second Type Superconductor up to the subcritical magnetic field, we act just like the First Type Superconductor, we can see the Meissner effect. However, if you exceed this value, some magnetic field will enter into your superconductor. It can still show superconducting properties. If you reach the upper critical magnetic field boundary, the superconducting property will disappear as you guessed.
The lower critical magnetic field value of the second type superconductors is low and the upper critical magnetic field value is high. As the upper critical magnetic field value is high, Second Type Superconducting materials are preferred in magnet making and technological applications.
Superconductors and Hellfire
We can say that everything has been reversed since scientists fought low temperature and discovered superconductors. They competed for a while to reach the critical temperature (0 Kelvin). They finally arrived, of course. Then they entered the era of producing superconducting materials at high temperature and perhaps at room temperature in the future.
Different temperatures are required to turn each element or alloy into a superconducting position. As they approached the critical temperature, they discovered new superconductors because, as such, some elements required even cooler temperatures to move into a superconductor position. After analyzing the elements that can be superconductors, different superconducting materials have begun to be developed. We have said that the Second Type of Superconductors are made of alloys, here are the high temperature superconductors of the Second Type.
In the 1980s, Nb3Ge was wearing the superconductor cape, which could operate at the highest temperature. He had a cloak with a temperature of 23.2 K and was throwing his air to everyone. In 1986, a discovery that would turn out its air came from K. Alex Müller and J. George Bednorz, who worked at Zürich IBM Research Labaratovars. This duo managed to create a superconductor at 35K.
Back then, both the Nobel BCS theory and many other theories did not predict that there would be superconductors above about 30K and considered this as the limit. But we can say that sweet physicists, who produce a ceramic made of lanthanum, barium, copper and oxygen, have done what these predictions will do. Of course, this shocking development in the physics world would not be gratuitous. As you suspect, these gentlemen took the Nobel Prize in Physics to their home the following year of their discovery.
After this development, the superconducting physicists must be surprised at what to do. I have to say at the end of the episode, but without removing much excitement, I remove the broad bean in my mouth. Today we have the honor of producing superconducting materials up to 200K!
When the year was 1987, a physicist named Paul Chu succeeded in producing superconducting material at 92 K. This development is considered a huge development. Because until this period superconducting materials were cooled with liquid helium, very cold liquids were required. As such, producing and storing these types of liquids was costly. Going over 92K enabled helium to be abandoned. Because the boiling degree of liquid nitrogen is 77 Kelvin. Since the production and storage of nitrogen is both easier and cheaper than helium, the nitrogen period has begun.
In 1988, superconductors were discovered at 120K. Then 125 K and then 134 K have been reached. They were able to increase this value to 166 K by applying pressure to our material consisting of mercury, barium, calcium, copper and oxygen, which are superconducting at 134K.
Nowadays, superconductor physicists see superconductors in their dreams at room temperature. This is everyone’s dream, I hope it will come true. Experimental physicists who produce different superconducting materials with different materials continue their research on the one hand and theoretical physicists who guide them on the other.
Physicists who produce a superconductor working at room temperature will of course be given the Nobel Prize in Physics immediately. I think it goes without saying how super-conductive physicists start with enthusiasm and enthusiasm. I conclude this article in the hope of giving the news of superconductor at room temperature one day.