Metallic hydrogen, which is under a pressure of about four and a half million atmospheres, may be the most critical transition temperature in the range of high temperature conductors.According to preliminary calculations, the Italo-German team of scientists of theoretical physicists, the critical temperature of the element is equal to 242 K (minus thirty-one degrees Celsius).
Hydrogen gas liquefies at a temperature of 20 C. If the temperature is still lower at 6 K, the element can be converted into the solid state.Hanington Wigner and in 1935 assumed the production of hydrogen in a laboratory.In their view, it was necessary to use a high pressure - about 25 GPa (GPa is approximately equal to one ten thousand atmospheres).Thus, under high pressure member to isotopes of hydrogen - a dielectric element conductive.It should be noted that the gas in the initial state has conductive properties.Just as metals, electrically conductive member, while it may not be in the solid state.In other words, hydrogen can be a liquid and having metallic properties.
In 1971 came the publication work of Soviet scientists and theorists headed by Kagan.A group of physicists argued that metallic hydrogen may be metastable.This means that, after exposure has ceased pressurized element goes into its original condition - a gas having insulating properties.At the same time it is still unclear whether this step is long enough to have time to make use of metallic hydrogen.
first success in the test plan was prepared in 1975, in February.A group of scientists headed by Vereshchagin created metallic hydrogen.Under the influence of a temperature of 4.2 K in a thin layer of the element using diamond anvils also subjected to a pressure of 300 GPa, there was a reduction of the electrical resistance of gas a million times.This indicated the transition of hydrogen into the metallic state.
For high pressure diamond anvil used.It is presented in the form of two artificial diamonds, acute pressed against each other by means of the press.As a result, the cut with a diameter - the order of several tenths of a millimeter, formed the necessary pressure.On this site in the cell is cooled sample.The sample in the same place the equipment supplied miniature thermocouples, electrodes and other measuring devices.
next stage in the work of scientists was to identify possible subsequent transition to the superconducting state of the metal.First Ask this problem Neil Ashcroft.Theorist predicted that metallic hydrogen will "exotic" properties at high temperatures above 200 K.
More recently came the work of the German and Italian physicists.The authors argue that due to the electron-phonon mechanism for the formation of Cooper pairs achieved record high critical temperature of - 242 C. At the same time, however, it is necessary and the impact of high pressure - about 450 GPa, and this, in turn, is four and a half milliontimes the atmospheric pressure.
When the electron-phonon formation of Cooper pairs motion in a periodic lattice in the crystal the electron is attracted nearest ions charged positively.Thus there is a slight deformation of the lattice, and for a short time, increases the concentration of positive charge.By increasing the concentration of the other electron is attracted.Thus, both electrons are attracted.At nonzero temperature fluctuation occurs ions about their equilibrium states.Phonons - quanta of this data fluctuations.
