Will we ever know all the states of matter? Instead of three, five hundred
Last year, the media circulated that “a form of matter has emerged” that could be called superhard or, for example, more convenient, albeit less Polish, superhard. Coming from the laboratories of scientists at the Massachusetts Institute of Technology, it is a kind of contradiction that combines the properties of solids and superfluids - i.e. liquids with zero viscosity.
Physicists have previously predicted the existence of a supernatant, but so far nothing similar has been found in the laboratory. The results of the study by scientists at the Massachusetts Institute of Technology were published in the journal Nature.
"A substance that combines superfluidity and solid properties defies common sense," team leader Wolfgang Ketterle, professor of physics at MIT and 2001 Nobel Prize winner, wrote in the paper.
To make sense of this contradictory form of matter, Ketterle's team manipulated the motion of atoms in a supersolid state in another peculiar form of matter called a Bose-Einstein condensate (BEC). Ketterle is one of the discoverers of BEC, which earned him the Nobel Prize in Physics.
“The challenge was to add something to the condensate that would cause it to evolve into a form outside of the 'atomic trap' and acquire the characteristics of a solid,” Ketterle explained.
The research team used laser beams in an ultra-high vacuum chamber to control the movement of the atoms in the condensate. The original set of lasers were used to transform half of the BEC atoms into a different spin or quantum phase. Thus, two types of BECs were created. The transfer of atoms between two condensates with the help of additional laser beams caused spin changes.
"Additional lasers provided the atoms with an additional energy boost for spin-orbit coupling," Ketterle said. The resulting substance, according to the prediction of physicists, should have been "superhard", since condensates with conjugated atoms in a spin orbit would be characterized by spontaneous "density modulation". In other words, the density of matter would cease to be constant. Instead, it will have a phase pattern similar to a crystalline solid.
Further research into superhard materials may lead to a better understanding of the properties of superfluids and superconductors, which will be critical for efficient energy transfer. Superhards may also be the key to developing better superconducting magnets and sensors.
Not states of aggregation, but phases
Is the superhard state a substance? The answer given by modern physics is not so simple. We remember from school that the physical state of matter is the main form in which the substance is located and determines its basic physical properties. The properties of a substance are determined by the arrangement and behavior of its constituent molecules. The traditional division of the states of matter of the XNUMXth century distinguishes three such states: solid (solid), liquid (liquid) and gaseous (gas).
However, at present, the phase of matter seems to be a more accurate definition of the forms of existence of matter. The properties of bodies in individual states depend on the arrangement of the molecules (or atoms) of which these bodies are composed. From this point of view, the old division into states of aggregation is true only for some substances, since scientific research has shown that what was previously considered a single state of aggregation can actually be divided into many phases of a substance that differ in nature. particle configuration. There are even situations when molecules in the same body can be arranged differently at the same time.
Moreover, it turned out that the solid and liquid states can be realized in a variety of ways. The number of phases of matter in the system and the number of intensive variables (for example, pressure, temperature) that can be changed without a qualitative change in the system are described by the Gibbs phase principle.
A change in the phase of a substance may require the supply or receipt of energy - then the amount of energy flowing out will be proportional to the mass of the substance that changes the phase. However, some phase transitions occur without energy input or output. We draw a conclusion about the phase change on the basis of a step change in some quantities that describe this body.
In the most extensive classification published to date, there are about five hundred aggregate states. Many substances, especially those that are mixtures of different chemical compounds, can exist simultaneously in two or more phases.
Modern physics usually accepts two phases - liquid and solid, with the gas phase being one of the cases of the liquid phase. The latter include various types of plasma, the already mentioned supercurrent phase, and a number of other states of matter. Solid phases are represented by various crystalline forms, as well as an amorphous form.
Topological zawiya
Reports of new "aggregate states" or hard-to-define phases of materials have been a constant repertoire of scientific news in recent years. At the same time, assigning new discoveries to one of the categories is not always easy. The supersolid substance described earlier is probably a solid phase, but perhaps physicists have a different opinion. A few years ago in a university laboratory
In Colorado, for example, a dropleton was created from particles of gallium arsenide - something liquid, something solid. In 2015, an international team of scientists led by chemist Cosmas Prasides at Tohoku University in Japan announced the discovery of a new state of matter that combines the properties of an insulator, superconductor, metal, and magnet, calling it the Jahn-Teller metal.
There are also atypical "hybrid" aggregate states. For example, glass does not have a crystalline structure and is therefore sometimes classified as a "supercooled" liquid. Further - liquid crystals used in some displays; putty - silicone polymer, plastic, elastic or even brittle, depending on the rate of deformation; super-sticky, self-flowing liquid (once started, the overflow will continue until the supply of liquid in the upper glass is exhausted); Nitinol, a nickel-titanium shape memory alloy, will straighten out in warm air or liquid when bent.
The classification becomes more and more complex. Modern technologies erase the boundaries between the states of matter. New discoveries are being made. The 2016 Nobel Prize winners - David J. Thouless, F. Duncan, M. Haldane and J. Michael Kosterlitz - connected two worlds: matter, which is the subject of physics, and topology, which is a branch of mathematics. They realized that there are non-traditional phase transitions associated with topological defects and non-traditional phases of matter - topological phases. This led to an avalanche of experimental and theoretical work. This avalanche is still flowing at a very fast pace.
Some people are again seeing XNUMXD materials as a new, unique state of matter. We have known this type of nanonetwork - phosphate, stanene, borophene, or, finally, the popular graphene - for many years. The aforementioned Nobel Prize winners have been involved, in particular, in the topological analysis of these single-layer materials.
The old-fashioned science of states of matter and phases of matter seems to have come a long way. Far beyond what we can still remember from physics lessons.
