Unsolved problems in physics: Why do certain materials exhibit superconductivity at temperatures much higher than 50 kelvins? Is room-temperature superconductivity possible?

The term High-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Müller in 1986. These materials are characterized by presenting superconductivity at a higher temperature than conventional superconductors (which require temperatures a few degrees above absolute zero (−273.15 °C or −459.67 °F)), and by other unconventional features. So-called high-temperature superconductors are generally considered to be those that demonstrate superconductivity at or above the temperature of liquid nitrogen, or −196 °C (77 K). January 2006 : January - February - March - April - May - June - July - August - September - October - November - December- → 31 January 2006 (Tuesday) U.S. President George W. Bush delivers the State of the Union Address to a joint session of the U.S. Congress (the House of Representatives and the Senate). ... Image File history File links Question_dropshade. ... This is an incomplete list of some of the unsolved problems in physics. ... A magnet levitating above a high-temperature superconductor (with boiling liquid nitrogen underneath) demonstrates the Meissner effect. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Mueller in 1986. ... The perovskite structure is adopted by many oxides with formula ABO3 and is very versatile having many useful technological applications such as ferroelectrics, catalysts, sensors and superconductors. ... Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικος (keramikos, having to do with pottery). The term covers inorganic non-metallic materials whose formation is due to the action of heat. ... Johannes Georg Bednorz (born May 16, 1950) is a German physicist who, along with Karl Alex Muller, was awarded the 1987 Nobel Prize for Physics for their joint discovery of superconductivity in certain substances at temperatures higher than had previously been thought attainable. ... Karl Alexander Müller (born April 20, 1927) is a Swiss physicist who, along with J. Georg Bednorz, was awarded the 1987 Nobel Prize for Physics for their joint discovery of superconductivity in certain substances at higher temperatures than had previously been thought attainable. ... 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... Conventional superconductors are materials that display superconductivity as described by BCS theory or its extensions. ... Absolute zero is a fundamental lower bound on the temperature of any macroscopic system. ... A degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701-1744), who first proposed a similar system in 1742. ... Fahrenheit is a temperature scale named after the German physicist Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ... Unconventional superconductors are materials that display superconductivity but that do not conform to BCS theory or its extensions. ... General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ... A degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701-1744), who first proposed a similar system in 1742. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ...

Recently, other unconventional superconductors have been discovered. Some of them also have unusually high values of the critical temperature T_c, and hence they are sometimes also called high-temperature superconductors, although the record is still held by a cuprate perovskite material (T_c=138 K, that is −135 °C). Nevertheless it is widely believed that if room temperature superconductivity is ever achieved it will be in a different family of materials. Unconventional superconductors are materials that display superconductivity but that do not conform to BCS theory or its extensions. ... The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Mueller in 1986. ... Perovskite (calcium titanium oxide, CaTiO3) is a relatively rare mineral occurring in orthorhombic (pseudocubic) crystals. ... A room temperature superconductor is material yet to be discovered which would be capable of exhibiting superconducting properties at temperatures above 0°C (273. ...

Despite its name, high-temperature superconductivity still occurs at cryogenic temperatures. The main difference from low-temperature superconductivity is usually that 'high-T_c' superconductors can use liquid nitrogen (at 77 K) as a coolant. A magnet levitating above a high-temperature superconductor (with boiling liquid nitrogen underneath) demonstrates the Meissner effect. ... Cryogenics is a branch of physics (or engineering) that studies very low temperatures or the production thereof. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... To help compare different orders of magnitude this page lists temperatures between 10 kelvins and 100 kelvins. ...

Most prominent materials in the high-T_c range are the so-called cuprates, such as La_1.85Ba_0.15CuO₄, YBCO (Yttrium-Barium-Copper-Oxide) and related substances. The term high-temperature superconductor was initially employed to designate the new family of cuprate-perovskite ceramic materials discovered by J.G. Bednorz and K.A. Mueller in 1986. ... Yttrium barium copper oxide, or YBCO, chemical formula YBa2Cu3O7-δ, is a high-temperature superconductor with a superconducting temperature of 94K. Its discovery by C.W. Chu in 1987 launched the era of high-temperature superconductors. ... General Name, Symbol, Number yttrium, Y, 39 Chemical series transition metals Group, Period, Block 3, 5, d Appearance silvery white Atomic mass 88. ... General Name, Symbol, Number barium, Ba, 56 Chemical series alkaline earth metals Group, Period, Block 2, 6, s Appearance silvery white Atomic mass 137. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ...

All known high-T_c superconductors are so-called Type-II superconductors. A Type-II superconductor allows magnetic field to penerate its interior in the units of flux quanta, creating 'holes' (or tubes) of normal metallic regions in the superconducting bulk. This property makes high-T_c superconductors capable of sustaining much higher magnetic fields. It has been suggested that Magnetic field density be merged into this article or section. ...

See also

• Superconductivity
• SQUID
• YBCO
• BSCCO
• Superconductivity in everyday life : Interactive exhibition