Bose-Einstein condensate. Its properties.

Almost 100 years ago, the Indian physicist Shatyendrant Bose, with an excessive mathematical bias, was engaged in the statistics of the distribution of light quanta (photons) and received the corresponding formula, which he sent to Einstein.

This formula was similar to Planck's formula, which the latter obtained by studying the radiation of a black body. This pleased Einstein, he translated Bose's article and gave it life. he wrote a couple more articles on this topic and the concept of a Bose gas was obtained, which is precisely controlled by the formulas written by Bose and Einstein. As it should be, these formulas contain exponentials, which, as usual, climb somewhere in some extreme regions. Integrals that diverge or give some ridiculous results. This is also influenced by the parameters of the formulas. One of them is temperature.

All this requires unusual interpretations and assumptions. Einstein suggested that cooling bosonic atoms to very low temperatures would cause them to fall (or "condense") to the lowest quantum state available, leading to a new form of matter. Moreover, there are already precedents. At zero degrees Celsius, we have ice, water and steam.

By this time (Einstein's assumption), all gases had already been liquefied and the phenomenon of superconductivity was discovered, but no one had received any condensate so far. In speed, the phenomenon of superfluidity was discovered, but there is still no condensate. Finally, Daniel Kleppner got down to business. Data taken from the video "Bose-Einstein condensate .

First, Kleppner's group tried to create a Bose-Einstein condensate in hydrogen, which they thought was the most suitable for such an experiment. But it turned out that everything is not so simple. The precipitate did not want to fall, although they tormented over it for a long time. The matter is at an impasse.

Two young scientists, Eric Cornell and Karel Wieman, moved to another location and decided to liquefy not light elements (hydrogen and lithium), but heavier ones, such as rubidium and cesium. In addition, they decided to use laser radiation for cooling. The point is that laser photons can both accelerate electrons and slow them down. In the first case, the accelerated electron will emit the next photon, accelerate and "squeeze" closer to the nucleus. The atom will simply shrink in size. Despite the fact that the speed of the electron has increased, collisions of atoms will decrease and the temperature will drop.

As you can see, this cooling problem was solved quite successfully purely intuitively. Laser irradiation cooled the gas by slowing down the movement of the atoms. But when liquefying gases, the method of their expansion is used. When expanding, gases are ejected from the nozzle at a high speed and are therefore cooled. What's the matter? Both are true, but interpretations of these phenomena are not complete. It would be necessary to add for complete clarity. In the first case, laser pulses caused an electron in an atom to emit a corresponding photon due to an increase in its speed, and the electron pressed closer to the nucleus and began to push less with other atoms. This affected the temperature drop.

It should be remembered that an increase in the kinetic energy of an electron due to an increase in its speed is much less than the loss of its internal energy in the form of a photon. And it turned out that the temperature loss due to the loss of internal energy turns out to be greater than the temperature increment due to the increase in kinetic energy.

Unfortunately, this cooling was not enough to obtain condensate. Hot atoms hovered over the cooled atoms and heated the already cooled atoms with their jolts. Hot atoms should be removed from the vessel. For this purpose, the technique of evaporative cooling was used. It consisted in the fact that around this vapor of fast (hot) atoms a corresponding magnetic field was created, the so-called magnetic trap, which pushed fast atoms out of the vessel.

This is how the scientist describes this phenomenon:

Look at this coffee. The steam rising above the mug is the hottest coffee molecules, which carry away more than a fair amount of energy with them. In the case of atoms, we keep them in a kind of magnetic vessel. We lock them there. They rush inside until they gain enough energy to jump out of it, taking energy from the remaining atoms inside. Accordingly, the atoms inside the vessel have less and less energy. They move more and more slowly and begin to accumulate at the very bottom. As this happens, we gradually lower the boundaries of the magnetic trap, so that at least a few atoms can always jump out until the rest of the atoms are finally collected at the very bottom of the vessel. The atoms are getting colder and colder and denser. And after a while, evaporation creates a Bose-Einstein condensate.

You can't say anything. Well done boys. But all the same, I would like to supplement their reasoning a little. Perhaps this will allow a little more accurate understanding of the processes occurring during condensation. It should be added that the atoms leaving the trap not only carry away part of the kinetic energy, but most importantly knock out much more internal energy from the remaining atoms. We see some of this energy on measuring instruments. In particular, a thermometer in the form of a thermocouple is also cooled and records the temperature of the cooled atoms. But the atoms of the measuring element are cooled not by the flying away atoms, but by the photons, which were knocked out of the remaining atoms by the flying away atoms. That is, in this case, the remaining electrons perform the function of a laser to cool a thermocouple or some kind of working fluid.

Soon after that, Kleppner managed to obtain hydrogen condensate as well. But he explained the theory of these processes with the help of wave-particle duality and the loss of their identity by particles. True, he realizes that all this is not clear and says:

Physics no longer knows such phenomena and it is difficult for a person to imagine it. So even simple reasoning gives me doubts and confusion.

It's actually simple:

In expansion chambers by accelerating atoms made them emitting a certain amount photons . As a result the electron of the atom lost part of its body, increased its speed, revolved around the nucleus faster and pressed closer to it. The atom has decreased in volume. This is approximately how we, by photographing the planets of the solar system, starting from the farthest, reduce the size of the entire solar system.

Further acting on the atom with the corresponding flux of laser photons, we began to remove photons of increasing energy from the electron. But it turned out that the photon knocked out of one electron sometimes turned out to be a decelerating photon for another electron of our substance. And in the end, a certain dynamic equilibrium occurred: the number of cooled and hot atoms did not change. The substance was no longer cooled.

This is where the guys thought of removing hot atoms from the system using a magnetic trap. The cold atoms stopped pushing and formed a precipitate called the Bose-Einstein condensate.

If we could shrink to the size of an atom, then we would see such a picture, in particular for hydrogen. An exchange photon and possibly a core, a small piece in the form of a droplet of an electric field, fly around the nucleus in waves. The photon reflected from the nucleus hits the core and condenses on it like a dew drop. Then this droplet (the final electron) begins to be attracted to the nucleus, which makes it turn again into an exchange photon. And this cycle can last forever.

As a result, we got a limit state atom with the corresponding properties:

1. It is much smaller than those that it had at normal temperatures. For this reason, condensate is highly fluid. It can even penetrate between the atoms of the crystal lattice. This is superfluidity .

2. Since the atom, or rather its electron, is in the limiting state or, as it is customary in science to say - a low-energy quantum state, or the ground state, . It cannot absorb any photons, except for photons one quantum below in energy than the energy of the exchange photon. And there are very few such photons. We knocked them out with difficulty using a laser. Undoubtedly, they are both in the solar stream and in the terrestrial stream, and can be obtained on an atom, as a sum of less energy-intensive photons. On the site N + 1 in the article "Bose condensate on the ISS showed a record free expansion time" it is said that the free expansion time after turning off the trap exceeded a second, and the effective temperature dropped below nanokelvin .

It is more difficult to obtain such a result on the ground, because the terrestrial photon flux directly on the ground contains more cooling photons, including those represented by gravitons, than on the ISS. There are not enough own hot atoms to heat up the condensate.

Thus, until the condensate heats up, its electrons cannot absorb photons of electric current. And if a current is passed through this condensate, then it will pass without loss. None of his photons will be lost. This is superconductivity .

3. Since the electron has almost disappeared from the atom, and it shields the positive field of the nucleus less, the atom turns out to be in this state with a greater positive potential than in its usual state. Such an atom can with great success “climb” along the walls of the vessel. great wettability appeared.

Approximately this is how the phenomenon of condensation of matter is seen from a quantum point of view without involving wave-particle duality, all kinds of copying of particles, finding them simultaneously in different places and other mysticism.

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