Research in the Gweon Group
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| The triumph of the BCS (Bardeen-Cooper-Schrieffer) theory is based on the distinction between these two: normal electron and superconducting electrons. At high temperature, normal electrons conduct the electricity. For instance, this is how the electricity conducts in Copper wires. If a metal is cooled down to very low temperature, it is often found to superconduct—the resistivity drops to zero, suddently (perfect conductor), and it expels any magnatic field (perfect diamagnet). According to the BCS theory, which is ''the'' theory of the superconductors that we have so far, the superconductivity occurs due to pairs of electrons (''Cooper pairs''). | The triumph of the BCS (Bardeen-Cooper-Schrieffer) theory is based on the distinction between these two: normal electron and superconducting electrons. At high temperature, normal electrons conduct the electricity. For instance, this is how the electricity conducts in Copper wires. If a metal is cooled down to very low temperature, it is often found to superconduct—the resistivity drops to zero, suddently (perfect conductor), and it expels any magnatic field (perfect diamagnet). According to the BCS theory, which is ''the'' theory of the superconductors that we have so far, the superconductivity occurs due to the movement of pairs of electrons (''Cooper pairs''). Recognizing this fundamental difference between the charge carriers of the normal conductor and the superconductor was the key to solving the superconductivity puzzle. == High temperature superconductivity == In 1987, Bednorz and Müller discovered the superconductivity in a very unlikely material—a Lanthanium Barium Copper oxide, which is essentially a ''ceramic'' material made to conduct with some charge carriers by chemical dopoing. Indeed, when they received the Nobel prize, the citation was ''for their important breakthrough in the discovery of superconductivity in ceramic materials.'' This was the beginning of the high temperature superconductivity puzzle! == Bad metal and good superconductor == If you are recalling a toilet bowl or a vase when you hear the word ''ceramic,'' you would be correct. High temperature superconductors seem to reveal the paradoxical truth of the superconductivity: certain bad matals become superconductors much more easily, i.e., has a higher transition temperature, than good metals. What this exactly means is the key question of the field today. In the Gweon group, we like to shed light on this issue by illuminating what are the essential features of the ''bad/strange metal'' phase. |
High temperature superconductivity?
The fundamental mystery of the high temperature superconductivity seems very deep. Here I will try to explain an important aspect of it, in a way that is, hopefully, understandable to any one.
The superconductivity
Let us think of the superconductivity, first, before thinking of the high-temperature superconductivity. It is a well-known fact that many heroes of the modern physics (Einstein, Feynmann, et al.) have tried to explain the superconductivity, and did not succeed. What was so difficult?
Normal electron and superconducting electrons
The triumph of the BCS (Bardeen-Cooper-Schrieffer) theory is based on the distinction between these two: normal electron and superconducting electrons. At high temperature, normal electrons conduct the electricity. For instance, this is how the electricity conducts in Copper wires. If a metal is cooled down to very low temperature, it is often found to superconduct—the resistivity drops to zero, suddently (perfect conductor), and it expels any magnatic field (perfect diamagnet). According to the BCS theory, which is the theory of the superconductors that we have so far, the superconductivity occurs due to the movement of pairs of electrons (Cooper pairs). Recognizing this fundamental difference between the charge carriers of the normal conductor and the superconductor was the key to solving the superconductivity puzzle.
High temperature superconductivity
In 1987, Bednorz and Müller discovered the superconductivity in a very unlikely material—a Lanthanium Barium Copper oxide, which is essentially a ceramic material made to conduct with some charge carriers by chemical dopoing. Indeed, when they received the Nobel prize, the citation was for their important breakthrough in the discovery of superconductivity in ceramic materials. This was the beginning of the high temperature superconductivity puzzle!
Bad metal and good superconductor
If you are recalling a toilet bowl or a vase when you hear the word ceramic, you would be correct. High temperature superconductors seem to reveal the paradoxical truth of the superconductivity: certain bad matals become superconductors much more easily, i.e., has a higher transition temperature, than good metals. What this exactly means is the key question of the field today. In the Gweon group, we like to shed light on this issue by illuminating what are the essential features of the bad/strange metal phase.