Success without pressure

Anonymous

Synopsis

Success without pressure

December 3, 2010• Physics 3, s168

Iron selenide is transformed into an ambient high-temperature superconductor by a purely chemical method, substituting extremely high pressure.

In the last two years, many distinct families of pnictide and chalcogenide superconductors have been discovered as a result of concerted efforts in this field. In almost all cases, an “ordinary” parent compound is turned into a superconductor either by chemical doping, or by application of pressure. One of the structurally simpler materials available is iron selenide, which has as basic building blocks layers of ${FeSe}_{4}$ tetrahedra. Application of extremely high pressure has yielded a superconducting critical temperature $T_{c}$ above $30 K$ , approximately half of the highest reported $T_{c}$ of $55 K$ in oxygen-deficient $SmFeAsO$ .

Now, in a Rapid Communication appearing in Physical Review B, Jiangang Guo and collaborators from the Chinese Academy of Sciences in Beijing, report the synthesis of $K_{x} {Fe}_{2} {Se}_{2}$ , a superconducting compound with a critical temperature $T_{c}$ slightly above $30 K$ at ambient pressure. That value sets a new record for the highest critical temperature at ambient pressure for this family of compounds. Structurally, these materials are related to the pnictide $122$ compounds $A {Fe}_{2} {As}_{2}$ ( $A = K, Sr, Ba$ ). In this case, the potassium is intercalated between the $FeSe$ layers, and the authors claim that the enhancement of $T_{c}$ is due to the optimization of the carrier density in the $FeSe$ layers and also due to the $Fe-Se$ tetrahedra achieving a shape close to the ideal. – Alexios Klironomos