Room temperature superconductor
Encyclopedia
A room-temperature superconductor is a material yet to be discovered which would be capable of exhibiting superconducting
properties at operating temperature
s above 0° C
(273.15 K
). This is not strictly speaking "room temperature" (approx. 20–25 °C), but it can be reached cheaply.
The discovery of a room temperature superconductor with a useful upper critical field
and critical current density could reduce the cost (of refrigeration) of current applications of superconductors and is likely to make many more applications possible or cost-effective.
now treat any further claims of this nature with extreme skepticism
..
In 2008 a Canadian-German team reported the discovery of superconductivity when silane
(SiH4) was compressed to a solid at high pressure.
Silane was unfortunately not a room-temperature superconductor; an EE Times
article grossly exaggerated this achievement and claimed that room-temperature superconductivity had been achieved. In reality, the transition temperature was 17 K at 96 and 120 GPa.
Palladium hydride: In 2003 a group of researchers published results on high-temperature superconductivity in palladium hydride
(PdHx: x>1) and an explanation in 2004.
In 2007 the same group published results suggesting a superconducting transition temperature of 260 K. The superconducting critical temperature increases as the density of hydrogen inside the palladium lattice increases.
An unverified claim of 'room temperature' superconductivity was made in 2000 by J. F. Prins within a phase formed on the surface of oxygen-doped type IIa diamonds in a 10-6 mbar vacuum. there is no record of any independent investigation which has either confirmed or disproved these results.
at extremely high pressure (~500 GPa) should become superconducting at approximately room-temperature because of its extremely high speed of sound
and expected strong coupling
between the conduction electrons and the lattice vibrations. This prediction is yet to be experimentally verified. As yet the pressure to achieve metallic hydrogen is not known but may be of the order of 500 GPa.
Prins could not explain superconductivity on the surface of type IIa diamonds in terms of Cooper pair
s, but he was able to do so in terms of a theory that he developed that uses a Wigner-type mechanism.
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
properties at operating temperature
Operating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
s above 0° C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(273.15 K
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
). This is not strictly speaking "room temperature" (approx. 20–25 °C), but it can be reached cheaply.
The discovery of a room temperature superconductor with a useful upper critical field
Upper critical field
-Upper critical field:The upper critical field is the magnetic field which completely suppresses superconductivity in a Type II superconductor at 0K ....
and critical current density could reduce the cost (of refrigeration) of current applications of superconductors and is likely to make many more applications possible or cost-effective.
Reports
Since the discovery of high-temperature superconductors, several materials have been reported to be room-temperature superconductors. In every case, independent investigation has quickly proven these claims false. As a result, most condensed matter physicistsCondensed matter physics
Condensed matter physics deals with the physical properties of condensed phases of matter. These properties appear when a number of atoms at the supramolecular and macromolecular scale interact strongly and adhere to each other or are otherwise highly concentrated in a system. The most familiar...
now treat any further claims of this nature with extreme skepticism
Skepticism
Skepticism has many definitions, but generally refers to any questioning attitude towards knowledge, facts, or opinions/beliefs stated as facts, or doubt regarding claims that are taken for granted elsewhere...
..
In 2008 a Canadian-German team reported the discovery of superconductivity when silane
Silane
Silane is a toxic, extremely flammable chemical compound with chemical formula SiH4. In 1857, the German chemists and Friedrich Woehler discovered silane among the products formed by the action of hydrochloric acid on aluminum silicide, which they had previously prepared...
(SiH4) was compressed to a solid at high pressure.
Silane was unfortunately not a room-temperature superconductor; an EE Times
EE Times
EE Times is an electronics industry newspaper published in the USA by UBM Electronics, a division of United Business Media. Launched in 1972 by Gerard G. Leeds of CMP Publishing. CMP was acquired by United in 1999...
article grossly exaggerated this achievement and claimed that room-temperature superconductivity had been achieved. In reality, the transition temperature was 17 K at 96 and 120 GPa.
Palladium hydride: In 2003 a group of researchers published results on high-temperature superconductivity in palladium hydride
Palladium hydride
Palladium hydride is metallic palladium that contains a substantial quantity of hydrogen within its crystal lattice. At room temperature and atmospheric pressure, palladium can absorb up to 900 times its own volume of hydrogen. This process is reversible...
(PdHx: x>1) and an explanation in 2004.
In 2007 the same group published results suggesting a superconducting transition temperature of 260 K. The superconducting critical temperature increases as the density of hydrogen inside the palladium lattice increases.
An unverified claim of 'room temperature' superconductivity was made in 2000 by J. F. Prins within a phase formed on the surface of oxygen-doped type IIa diamonds in a 10-6 mbar vacuum. there is no record of any independent investigation which has either confirmed or disproved these results.
Theory
Theoretical work by Neil Ashcroft predicted that solid metallic hydrogenMetallic hydrogen
Metallic hydrogen is a state of hydrogen which results when it is sufficiently compressed and undergoes a phase transition; it is an example of degenerate matter. Solid metallic hydrogen is predicted to consist of a crystal lattice of hydrogen nuclei , with a spacing which is significantly smaller...
at extremely high pressure (~500 GPa) should become superconducting at approximately room-temperature because of its extremely high speed of sound
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....
and expected strong coupling
Coupling (physics)
In physics, two systems are coupled if they are interacting with each other. Of special interest is the coupling of two vibratory systems by means of springs or magnetic fields, etc...
between the conduction electrons and the lattice vibrations. This prediction is yet to be experimentally verified. As yet the pressure to achieve metallic hydrogen is not known but may be of the order of 500 GPa.
Prins could not explain superconductivity on the surface of type IIa diamonds in terms of Cooper pair
Cooper pair
In condensed matter physics, a Cooper pair or BCS pair is two electrons that are bound together at low temperatures in a certain manner first described in 1956 by American physicist Leon Cooper...
s, but he was able to do so in terms of a theory that he developed that uses a Wigner-type mechanism.
External links
- http://arxiv.org/abs/cond-mat/0606187 - a book
- http://xxx.lanl.gov/abs/0704.2188 - a chapter
- J F Prins paper
- http://www.google.com/patents?id=AQE5AAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q&f=false
- A patent for an RTS that has yet to be debunked.