Room temperature superconductors

Trains that run on frictionless tracks and computer chips smaller than those of the present generation yet faster and with much larger capacities—these are potential applications of room-temperature superconductors. Research groups around the world are developing new materials in hopes of reaching this spectacular goal. 

The object of the workshop was the quantum mechanism that allows the macroscopic quantum coherence of a superconducting condensate to resist to the attacks of high temperature. Solution to this problem of fundamental physics is needed for the design of room temperature superconductors, for controlling the decoherence effects in the quantum computers and for the understanding of a possible role of quantum coherence in living matter that is debated today in quantum biophysics. 

The practical significance of the discovery, apart from the fact that it suggested the possibility of a room temperature superconductor, is that the Tc is above the boiling point of liquid nitrogen ( 77K), a cheap refrigerant. 

Twenty-five years ago, Stanford s William Little startled the general public with his predictions of plastic materials that had no electrical resistance at high temperatures, room-temperature superconductors, flying carpets, superconducting skis, trains that levitated over tracks and glided smoothly along at 300 miles per hour, and frictionless electrical transmission lines. 

Little s ideas were intriguing to anyone who delighted in science fiction, but a source of dismay for his scientific colleagues. Lamented the New Scientist in London It is highly disappointing that the possibility of a room-temperature superconductor has been removed. The technological... 

He discusses the advantages of an S/C system and what might be expected from the higher-Tc materials, including the effects a room-temperature superconductor would have on the design of ships engines in the future ... 

Can these superconducting motors and bearings be combined to create that nonpolluting, quiet, simple-starting dream vehicle, the electric car Perhaps. Room-temperature superconductors seem to be close at hand, and engineers have been able to build smaller motors and chassis with lighter materials, and space-age fuel cells that are similar to batteries but which draw their energy from a chemical fuel that is supplied while the cell is in use. 

Clearly, we need a multiple-sensor system that can simultaneously measure the magnetic field at various positions over the scalp—say, one hundred positions—so that measurements could be completed in a matter of minutes. This would enable us to see patterns of activity as they shift from one area of brain to the next. The problem, though, is that we have to keep the sensors, the detector coils, very cold in liquid helium. You also need a good Dewar, and the present ones are rigid structures. It doesn t take you long to realize, when you study human heads, that they come in different sizes and shapes—round ones, flat ones, heads with corners and edges. To maximize sensitivity, you have to get those coils closer to the head, and we don t have that flexibility with current designs. If we had a room-temperature superconductor, we could do that very easily, because they d all be on tracks that could slide in nicely and you could fit them to a child. 

From what we know now, it is not going to be easy to make practical room-temperature superconductors. For one thing, scientists believe that getting a superconductor to carry more than a trickle of electrical current at room temperature would be very difficult. Even if we had room-temperature superconductivity, we would probably still work at the liquid nitrogen temperature, at which the current-carrying capacity of the superconductors is much greater. 

While the possibility of achieving yet higher temperatures in new compositions continues to be actively pursued, we focus in what follows on the most studied group of superconductors with transition temperatures in the range from 99-100 K, namely the YBa2Cu307 5 group with the "123" layered perovskite superstructure 51, which we henceforth refer to as YBaCuO. Certainly the possibilities for application would be increased immeasurably if stable room temperature superconductors were found. 

A/cm2 at 77 K, more than an order of magnitude lower than at 4.2 K. Thus YBaCuO at 77 K has a fundamental disadvantage in zero-field critical current density compared to, say, Nb3Sn at 4.2 K. The same effect impacts the hope for practical room temperature superconductors To maintain reasonable critical current density at 300 K or 27 C, the superconducting transition would have to be closer to 400 K or 127 C ... 

What is a superconductor and why is the discovery of a room-temperature superconductor an important goal ... 

Before 1986, most scientists were skeptical that a room-temperature superconductor would ever be discovered, but in the twenty-first century such a discovery seems increasingly hkely. If such a superconductor could be efficiently and economically manufactured, then most industries of modern society would be affected, and a superconductor revolution would occur, similar to the computer revolution of the second half of the twentieth century. 

Room-temperature superconductivity would transform the electrical-power, transportation, and consumer-electronics industries. The era of copper s dominance would end, leading to a new generation of smaller and more efficient home appliances, such as refrigerators, washing machines, and air conditioners. Societies whose technologies make use of these room-temperature superconductors would he quieter, cleaner, and more energy efificient... 

Though this idealistic view of the future motivates many researchers, realists caution that, based on the previous century of superconductivity research and development, the path to the elusive room-temperature superconductor will not he smooth and straight Furthermore, those traveling this path should he prepared for unexpected difficulties as well as pleasant surprises. 

Superconductivity at room temperature is sometimes a subject of science fiction or fantasy. For example, in the movie Terminator 2 Judgment Day, a cyborg has a CPU that contains a room-temperature superconductor. How might a computer with such a CPU differ in design lirom current computers ... 

Superconductivity of perovskites toward a room-temperature superconductor... 

The quest for a room temperature superconductor has spurred the development of thousands of compounds incrementally driving the critical temperature for superconduction to higher values. Table 3.21 shows various superconducting materials with corresponding... 

Now if a semiconductor organic solid with a few electrons in the conduction band were to interact with the exciton field the uo would be replaced by wOgx The frequence ex and one has the hope of a room temperature superconductor. We shall outline a model /5/ which gives these results. 

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