Received: June 12, 2019 Accepted: June 21, 2019 Published: June 22, 2019
We review the physics of high temperature superconductors. We start by looking at the experimental facts and giving a general overview of the cuprate superconductors. Using this as motivation, we follow Anderson’s ideas for constructing a coherent theoretical framework. Our discussion is guided by a set of Central Dogmas based on experimental observation that we use to constrain the structure of any theory of the cuprates. We make speculations about a possible driving force for the large critical temperatures, and present possible pairing The history of high Tc superconductors (HTSc) was begins in IBM research laboratory (1986) with the discovery of Ba-La-Cu-O superconductor having the critical temperature 36 K by Karl Muller and Johannes Bednorz. This opened a new mode of high Tc superconductivity namely “High Temperature Superconductivity” as they has been broken the barrier point of 30 K imposed by BCS theory. Soon after this event, many other oxide based superconductors were discovered having the Tc greater than 90 K and they are shown below in Figure 1.5 with Tc and their respective discovery year. History and progress LBCO: LBCO (Lanthanum Barium Copper Oxide) was the first oxide based HTSc material developed in 1986 having Tc of 35 K. It is the only insulating material in HTSc family. This discovery provides the path for the additional research in high Tc superconductivity on cuprate materials with structure similar to LBCO . YBCO: YBCO (Yttrium Barium Copper Oxide) was discovered in the year 1987 by Paul Chu in the University of Houston and it shown the highest Tc of 93 K. It is the first the first material to break the liquid nitrogen temperature (77 K). YBCO is highly studied as it is the cleanest and most ordered crystals and shows strong electron- electron interaction . BSCCO: BSCCO (Bismuth Strontium Calcium Copper Oxide) was the first high temperature superconductor which did not contain a rare earth element. It is a cuprate superconductor which shares a two dimensional layered Perovskites structure with the superconducting copper oxide plane. General formula for BSCCO is Bi2Sr2Can1CunO2n+4+x with specific transition temperature ranging from Tc = 20 K (n=1, 2201 phase), 85 K (n=2, 2212 phase), 110 K (n=3, 2223 phase) and 104 K (n=4, 2224 phase) . TBSCCO: TBSCCO (Thallium Barium Calcium Copper Oxide) was discovered in the same year as BSCCO. It is next higher member of HTSc family and general formula is Ti2Ba2Can-1CunO2n+2+x with transition temperature ranging from Tc= 85 K (n=1, 2201 phase), 110 K (n=2, 2212 phase) and 127 K (n=3, 2223 phase). In this superconductor, CuO2 layers are thicker and closer together in comparison to BSCCO system. HBCCO: HBCCO (Mercury Barium Calcium Copper Oxide) is the highest member of the HTSc family (2009) till date. It has general formula Hg1Ba2Can-1CunO2n+2+x with specific transition temperature ranging from Tc= 94 K (n=1, 1201 phase), 128 K (n=2, 1212 phase) and 134 K (n=3, 1223 phase).