This work began in 1975, during the completion of a diploma project at the Moscow Institute of Electronic Technology. Then I wanted to create a film active element using hot electrons. But when I learned about the Ginzburg-Kirzhnits hypothesis, proposed in 1963, I realized that the sandwiches that I had to create exactly met the requirements of this hypothesis.

In 1957 Bardeen-Cooper-Schrieffer created the theory of superconductivity, where the main role in the phenomenon of superconductivity was assigned to the formation of paired electrons through interaction with phonons and the critical temperature of the transition of a metal to the state of superconductivity is determined by a certain characteristic temperature of phonons. This characteristic temperature is approximately equal to the Debye temperature of phonons, and the critical temperature of the transition of the metal to the superconducting state is determined by the formula:

where g a constant proportional to the force of attraction between electrons. Since the Debye temperature of phonons cannot exceed several hundred degrees, a rough estimate of the phonon mechanism of superconductivity at that time showed that the critical temperature of the phonon mechanism cannot exceed 25°K. Therefore, Ginzburg - Kirzhnits proposed using other particles to pair electrons, for example electron excitons type. Since the Debye temperature of excitons can be thousands and even tens of thousands of degrees, rough theoretical calculations have shown that the critical temperature of the excitonic mechanism for the transition of a metal to the superconducting state can reach 300 ° K or more, which corresponds to room temperature and above. This is how the design of the Ginzburg-Kirzhnitz sandwich for the exciton mechanism of superconductivity was born, which you see in Fig. 1, although now I know for sure that in such a sandwich electron pairing will never occur through interaction with excitons.

Fig.1 Sandwich for the exciton mechanism of superconductivity.

Moreover, I can say that during the development of the excitonic theory of high-temperature superconductivity, an inaccuracy was made in calculating the electron wave functions, so the critical temperature of the exciton mechanism can reach not only room temperature, but also exceed it several times. At that time, I had the opportunity to meet with one of the developers of the theory of high-temperature superconductivity. When I asked him whether an excitonic mechanism of superconductivity could arise in a structure consisting of metal balls measuring several interatomic distances, surrounded by a thin layer of dielectric and compressed to interatomic distances. He replied that it is in such structures that it should be observed. Since then, he began to create multi-layer sandwiches, in which the main layer had the above-mentioned structure. At the end of the thesis project, I discovered that on several samples there are current jumps in the current-voltage characteristics, and their conductivity changes by an order of magnitude at a certain voltage. This is shown in Fig. 2. Figure 3 shows a typical characteristic of superconductor-insulator-superconductor structures.

Fig.2 V.A.H. samples measured in 1976

Fig. 3 Typical current-voltage characteristics of structures superconductor insulator superconductor.

Such behavior of the current-voltage characteristic in the studied phenomena exists only in superconductor-insulator-superconductor structures (S - I -S). I again met with one of the developers of the high-temperature theory, and I managed to convince him that such characteristics can be given by structuresS-I-S. He did not believe in these results, since they theoretically proved that it is practically impossible to implement the exciton mechanism of superconductivity in practice, since the metal must have a thickness of 5Å, and this is one atomic layer, which is impossible to obtain. But theory is theory, and practice remains the criterion of truth.

I thought that, having arrived in Voronezh on assignment, I could immediately continue working. But fate turned out differently. And when I read the article in 1987. about the discovery of superconducting ceramics, where it was written when Müller came to Bednorz and asked how to create a structure consisting of metal balls of several interatomic sizes, surrounded by a thin layer of dielectric and compressed to interatomic distances. He responded by sintering ceramics. This is how superconducting ceramics was born; the critical temperature, which at that time reached 112°K. After that, I thought that they would soon reach room temperature. The only thing that consoled me a little was that the samples were obtained not by sintering ceramics, but by natural cultivation in certain environments. After this message I completely abandoned superconductivity. But almost twenty years have passed since the discovery of superconducting ceramics, and there have been no reports of the discovery of superconductivity at room temperature.

In December 2002 I got the idea to once again examine samples made almost 30 years ago. I came to the garage, opened my student's suitcase and brought them to the laboratory. And now about what I saw on them.

In Fig.4 , rice.5 , rice.6 , you see three graphs and VAC., Upsemi whatborn in 1976, in the center there is a typical current-voltage characteristic. for structures S-I-S,At the bottom CVC. samples measured in 2002

Fig.4 V.A.H. measured in 1976

Fig.5 Typical V.A.H. S-I-S structures.

Fig.6 V.A.H. measured in 2002

All of them have three characteristic sections, initial with high resistance, then when the voltage reaches 2Δ / e , a current jump, and the third as in conventional tunneling in metal-insulator-metal structures. But if the obtained characteristics are associated with the phenomenon of superconductivity, then there must be a critical temperature at which superconductivity disappears. When connecting samples to a direct current source, on the current-voltage characteristic. a gestiresis loop is observed. Moreover, the width of gestiresis is a function of temperature and at a critical temperature becomes equal to zero. In Fig. 7 you see the dependence of the gestiresis width on temperature.

Fig. 7. Dependence of the width of gestiresis on temperature:

a) at 77.°K, b) at 300.°K, c) at 620°K.

It can be assumed that in such complex layered sandwiches, hysteresis can be caused by mobile ions. But in this case, with decreasing temperature, the width of gestiresis should decrease, since the mobility of ions decreases. And in the graphs of Fig. 7 we see the opposite picture: with decreasing temperature, the width of gestiresis increases, which is typical only for structures S-I-S. Based on these results, we can conclude that the critical temperature of transition to the superconducting state of the samples under study is approximately 620°K. or 350°C.

If these samples are superconducting, then Josephson effects should be present on them. By dividing the sample into parts, areas were identified where the thickness of the dielectric between the metals did not exceed 20 Å. When measuring selected samples on curve tracers, when applying an alternating voltage with a frequency of 50 Hz. an ellipse was observed on the screen. You can see this in Fig. 8

Fig.8. Ellipse on alternating voltage.

Fig.9. Ellipse plus pulsesstep generator.

As one Moscow professor told me: an ellipse as an ellipse has nothing interesting in it. Indeed, it has the correct geometric shape and there is nothing interesting in the ellipse itself. The interesting thing is how it was obtained on the characterograph screen. There are two ways to obtain an ellipse: from one signal source through an R-C chain or from two signal sources. The first option was simulated using a computer program. As the ellipse approached the vertical or horizontal axis, the ellipse degenerated into a straight line. And as you see in Fig. 8, the ellipse is almost horizontal. This means that the ellipse was obtained using two signal sources. If one signal source is a curve tracer, then the second signal source can only be the sample under study. If you look at fig. 9 on another curve tracer, then when the step generator is turned on, pulses of the step generator are observed on the ellipse. The sample behaves in such a way that whatever signal it receives is what it generates. I know that nothing is known about low-frequency generation by Josephson junctions. But this is easy to check for those who have the opportunity to work with these transitions. It is enough to connect one of the superconductors through the capacitance and on the curve-character screen you will observe an ellipse and pulses and any other signal that is used in the curve-character.

To study samples at direct current, the capacitance was removed. The sample was connected to the curve tracer as to a direct current source. As a result, at zero voltage across the sample, a direct current flowed through it. You can see this in Fig. 10. In superconductivity, such a current is called a constant superconducting Josephson current and is caused by the tunneling of Cooper pairs when their phase coherence is violated.

Fig. 10. Superconducting current, at zero voltage on the sample.

Fig. 11. Dependence of superconducting current on magnetic fields.

Fig. 12. ControlWithsuperconducting electric shock

If this is a superconducting current, then in a magnetic field it should give a diffraction pattern. The experiment was carried out using permanent magnets, and the distance between the magnet and the sample varied. The current was measured as a function of the distance between the magnet and the sample. You can see the results obtained in Fig. 11. The tilt to the left, according to the theory of superconductivity, is associated with the addition of its own magnetic field to the external field, which occurs at high currents through the junction. I want to say right away that when examining separately each layer that makes up the sandwich, none of the above characteristics were observed. Therefore, it can be assumed that the formation of Cooper pairs occurs through the interaction of electrons in the main layer with particles in another layer. Perhaps this is an excitonic mechanism. And if this is so, then with the help of an additional metal electrode existing in the sandwich, the superconducting current can be easily controlled. When pulses from the step generator were applied to the additional electrode, a family of output characteristics appeared on the curve graph screen. You can see this in Fig. 12. It resembles a family of transistor output characteristics. Therefore, using the effect of controlling superconducting current, it is possible to create active elements for converting and amplifying electrical signals. Devices created using this effect will be able to operate at temperatures from 0°K. up to 620°K. and at frequencies above 100 GHz. Thus, in Fig. 12 you see the characteristics of the first superconducting active device for converting and amplifying electrical signals.

And now about the study of absorption and emission of microwave electromagnetic waves. The sample was connected to the curve tracer as a voltage source. The initial section of the Josephson junction can be seen in Fig. 13.

Fig. 13. Initial section of the current-voltage characteristic.

Fig. 14. Current-voltage characteristic. when exposed to Microwave electromagnetic waves.

Fig. 15. Structure of the main layer.

At the beginning of the section, hysteresis is observed, the width of which depends on the magnetic field. When a magnetic field is applied, the width of the gestiresis increases. This transition was exposed to microwaves. radiation, and the results are presented in Fig. 14. As you can see, as a result of the absorption of electromagnetic waves, a horizontal step was formed. The magnitude of this step in volts is related to the frequency of irradiation, the charge of the electron and Planck's constant. Preliminary measurements and calculations of Planck's constant show that its value coincides with the table value with an accuracy of 0.02 percent. To improve accuracy, calibrated measuring instruments are needed. And now about the radiation of electromagnetic waves. If you increase the current flowing through the sample, red-violet plasma balls form above the surface, which corresponds to air plasma. This occurs when the intensity of the emitted microwaves. electromagnetic waves reaches values ​​sufficient to ionize air molecules. As a result of the formation of plasma beads, a trace is formed on the surface of the sample, which slightly reveals the structure of the material of the main layer of the sandwich. You can see this in Fig. 15. The photo was taken at very high magnification, so the clarity is not very good.

Now let's discuss the results obtained. I had to meet with scientists and specialists. Some of them try to explain the results obtained by contact phenomena, although they do not say which ones. Therefore, I would like to say that it seems that they have a poor understanding of the characteristics of contact phenomena and, especially, tunnel phenomena in structures S-I-S. Others agree that all the given characteristics correspond to the structuresS-I -S, but to confirm superconductivity it is necessary to measure the diamagnetic susceptibility of the samples, since upon transition to the superconducting state all materials become strong diamagnetic. I agree with this. But let's approach this issue from the other side. Let’s say we are researching the diamagnetic properties of materials, we don’t know the results given in this work, and these structures come to us. We detect strong diamagnetism on them at room temperature, like superconductors. Can we say that this is superconductivity? Of course not, since the main property of superconductivity is when the resistance of the conductor becomes zero. If you look at fig. 10, then at zero voltage a current flows through the sample. And this just confirms that the resistance of the sample is zero. In addition, all Josephson effects are associated only with tunneling of Cooper pairs, and in the samples under study we observe almost all Josephson effects. This means that it can be argued that Cooper pairs exist in the samples under study, and the existence of Cooper pairs is the main condition for the occurrence of superconductivity, according to the BCS theory. During the research, a critical temperature and current were discovered, and the samples in a magnetic field behave in the same way as superconductor-insulator-superconductor structures. Therefore, there is no doubt that metal balls surrounded by a thin layer of dielectric are in a state of superconductivity at room temperature and above. We will conduct diamagnetic studies of the samples as soon as possible. But there is no doubt that the diamagnetic properties of the samples will be the same as those of conventional superconductors, since in nature there are no two different phenomena that exhibit the same properties. Thank you for your attention. I will be grateful to everyone who can provide support and assistance in this work.

Literature:

1. Ginzburg V.L., Kirzhnits D.A. The problem of high-temperature superconductivity - M.: Nauka, 1977. – 400 p.

2.Bukkel V. Superconductivity. – M.: Mir, 1975.-364 p.

3. Solimar L. Tunnel effect in superconductors. – M.: Mir, 1974.- 428 p.

4. Derunov V. Website

Illustration copyright Thinkstock Image caption Superconductors can be used to create electrical networks

At approximately -270 degrees Celsius, some metals allow electric current to pass without resistance. However, scientists have learned to achieve superconductivity at a higher temperature of about 130 Kelvin (-143 Celsius), and do not stop there, believing that this valuable property can be reproduced at room temperature.

Superconductors are characterized by a complete absence of resistance. So-called type I superconductors completely displace the magnetic field.

Similar type II substances allow the presence of superconductivity and a strong magnetic field at the same time, which makes their range of applications extremely wide.

What is superconductivity?

The phenomenon itself was described by the Dutch chemist and physicist Heike Kammerling-Ottes in 1911. He won the Nobel Prize two years later.

The concept of superconductivity first appeared in the scientific works of Soviet academician Lev Landau, who, by the way, also received the Nobel Prize for his work in 1962.

The superconductivity of metals is explained using the concept of so-called “Cooper pairs”: two electrons united through a quantum with a total of zero angular momentum.

Similar electron pairings occur in the crystal lattice of some metals when cooled to extremely low temperatures.

However, later, with the help of cuprates - ceramics with a high copper content - scientists achieved the emergence of superconductivity at temperatures significantly higher than the boiling point of nitrogen (-196 Celsius), which, given the widespread production of liquid nitrogen, makes substances with no resistance relatively convenient to use.

Thanks to these experiments, superconductors became widespread and are used today, in particular, for imaging in medical diagnostic devices such as magnetic scanners and magnetic resonators.

They are also widely used in particle accelerators in physics research.

And then graphene?

Professor of the Aalto University Helsinki and the Landau Institute of Theoretical Physics of the Russian Academy of Sciences Grigory Volovik, within the framework of the Moscow International Conference on Quantum Technologies, spoke about the possible achievement of superconductivity at high temperatures using graphene, a flat modification.

Graphene, like superconductors, is predicted to have a bright future - manufacturers of both light bulbs and body armor are interested in it, not to mention its prospects in microelectronics.

Illustration copyright IBM Image caption Under normal conditions, graphene exhibits the properties of a semiconductor

Theoretical physicists described its potential throughout the 20th century, but it came to practical research only in the 21st century: it was for the description of the properties of graphene isolated from graphite that natives of Russia Konstantin Novoselov and Andrei Geim.

According to Volovik, knowledge about the properties of electromagnetic fields could make it possible to build a superconductor based on flat energy bands that can be observed in “ideal” graphene.

And yet - what to do with room temperature?

The flat zone characteristic of ideal graphene should have zero energy throughout its entire plane.

However, the actual structure of a two-dimensional allotropic modification of carbon often resembles a “flattened sausage” in structure, says Professor Volovik.

Nevertheless, experts are not discouraged: at the moment, theorists are working on several options for the appearance of the flat energy zone necessary to create superconductivity in room conditions, including supercooled gases.

Last year, American physicists from Stanford University realized how graphene’s superconductivity can be put into practice using layers of monatomic carbon - actually graphene - and calcium superimposed on each other in a “sandwich”.

Since a little more than a year ago, British scientists, we can talk about a noticeable reduction in the cost of production of the necessary materials.

The challenge, as all the experts mentioned above say, is now to find ways to produce defect-free graphene in large volumes.

Solid, liquid, gas, plasma... what else?

One of the states of matter for which superconductivity and other quantum effects are observed is the Bose-Einstein condensate, named after the theoretical work of Indian physicist Satyendra Bose and Albert Einstein.

Illustration copyright Science Photo Library Image caption Satyendra Bose pioneered the study of particle behavior at zero Kelvin

It is a special form of matter - it is a state of aggregation of photons and other elementary particles related to bosons, at temperatures close to zero kelvins.

In 1995 - 70 years after the release of theoretical justifications by Bose and Einstein - scientists were able to observe condensate for the first time.

Only in 2010 did physicists manage to obtain such a condensate for photons.

In particular, Natalya Berloff, a teacher at the Skolkovo Institute of Science and Technology, who spoke at the conference, described the behavior of polaritons - quasiparticles that arise when photons interact with elementary excitations of the medium.

Berloff said she tried to present the application of quantum theory to Prime Minister Dmitry Medvedev and Deputy Prime Minister Arkady Dvorkovich last summer as a national initiative.

Some of the students of the Skolkovo Institute of Science and Technology are already actively participating in international research - in particular, Berloff's students are part of a team of physicists describing the behavior of the mentioned polaritons.

MOSCOW, September 13 - RIA Novosti. Individual grains of graphite can exhibit superconducting properties at room temperature after being treated with water and baked in an oven, suggesting that superconductivity can be achieved under normal conditions in practice, German physicists say in a paper published in the journal Advanced Materials.

“Overall, the data from our experiment indicate that superconductivity at room temperature is feasible, and that the methods we used could pave the way for a new generation of superconductors, whose emergence will bring benefits to humanity that are still difficult to assess,” said the leader of the physics team, Pablo Esquinazi ( Pablo Esquinazi) from the University of Leipzig (Germany).

Esquinazi and his colleagues studied the physical properties of graphite and other forms of carbon. In one experiment, scientists poured graphite powder into a test tube with water, stirred it and left it alone for 24 hours. After this, physicists filtered the graphite and dried it in an oven at a temperature of 100 degrees.

As a result, scientists obtained a set of graphite granules with extremely interesting physical properties. Thus, the surface of these grains has superconducting properties that persist even at a temperature of 300 degrees Kelvin, or 26 degrees Celsius.

This manifested itself in the appearance of characteristic sharp phase transitions of the magnetic moment inside the grains, which exist in classical high-temperature superconductors. Physicists have never been able to verify whether graphite has two other main features of such materials: the absence of resistance and the so-called Meissner effect - the complete displacement of the magnetic field from the body of the conductor.

However, the discovery of even one of the effects suggests that high-temperature superconductors can function at room temperature.

Unfortunately, the graphite grains obtained by Esquinazi and his colleagues cannot be used as a “building material” for superconductors. Firstly, only 0.0001% of the mass of graphite has superconducting properties due to the fact that this effect is observed only on the surface of the grains. Secondly, this form of graphite is extremely fragile, and the physical properties of the grains are lost irrevocably even with the slightest deformation.

In their subsequent work, physicists plan to study the surface of the grains and the role of hydrogen atoms that remain on their surface after the “water bath” and subsequent drying. In addition, Esquinazi and his colleagues will test whether such grains have zero resistance and whether the Meissner effect occurs in them.

Superconductivity is one of the most mysterious, remarkable and promising phenomena. Superconducting materials, which have no electrical resistance, can conduct current with virtually no loss, and this phenomenon is already being used for practical purposes in some areas, for example, in the magnets of nuclear tomography machines or particle accelerators. However, existing superconducting materials must be cooled to extremely low temperatures in order to achieve their properties. But experiments conducted by scientists this year and last have yielded some unexpected results that could change the state of superconductor technology.

An international team of scientists, led by scientists from the Max Planck Institute for the Structure and Dynamics of Matter, working with one of the most promising materials - the high-temperature superconductor yttrium-barium-copper oxide (YBa2Cu3O6+x, YBCO) , discovered that exposing this ceramic material to pulses of light from an infrared laser causes some of the material's atoms to briefly change their position in the crystal lattice, increasing the manifestation of the superconductivity effect.

Crystals of the YBCO compound have a very unusual structure. On the outside of these crystals there is a layer of copper oxide covering intermediate layers containing barium, yttrium and oxygen. The effect of superconductivity when irradiated with laser light occurs precisely in the upper layers of copper oxide, in which intensive formation of electron pairs, the so-called Cooper pairs, occurs. These pairs can move between crystal layers due to the tunneling effect, and this indicates the quantum nature of the observed effects. And under normal conditions, YBCO crystals become superconductors only at temperatures below the critical point of this material.

In experiments conducted in 2013, scientists found that shining a powerful infrared laser on a YBCO crystal caused the material to briefly become a superconductor at room temperature. It is obvious that laser light affects the adhesion between layers of material, although the mechanism of this effect remains not entirely clear. And to find out all the details of what was happening, scientists turned to the capabilities of the LCLS laser, the most powerful X-ray laser to date.

“We started hitting the material with pulses of infrared light, which excited some of the atoms, causing them to vibrate with a fairly strong amplitude.”
- says Roman Mankowsky, a physicist from the Max Planck Institute, -“We then used an X-ray laser pulse immediately following the infrared laser pulse to measure the exact amount of displacement that occurred in the crystal lattice.”

The results showed that the pulse of infrared light not only excited the atoms and caused them to vibrate, but also caused them to shift out of position in the crystal lattice. This made the distance between the copper oxide layers and other layers of the crystal smaller for a very short time, which in turn led to an increase in the manifestation of the quantum coupling effect between them. As a result, the crystal becomes a superconductor at room temperature, although this state can last only a few picoseconds of time.

“The results we obtained will allow us to make some changes and improve the existing theory of high-temperature superconductors. In addition, our data will provide invaluable assistance to materials scientists developing new high-temperature superconducting materials with a high critical temperature.” - says Roman Mankovsky, -“And ultimately, all of this, I hope, will lead to the dream of a room-temperature superconducting material that requires no cooling at all. And the emergence of such a material, in turn, could provide a host of breakthroughs in a great many other areas that take advantage of the phenomenon of superconductivity.”