High temperature superconductivity

1. For copper-based superconductors, the maximum superconducting transition temperature Tc,max of different families measured from experiments can vary from 38 K in La2CuO4 to 135 K in HgBa2Ca2Cu3O8 at the optimal hole doping concentration. We demonstrate in a recent work on Physical Review Letters, using ab initio computations, a new trend suggesting that the cuprates with stronger out-of-CuO2-plane chemical bonding between the apical anion (O,Cl) and apical cation (e.g., La, Hg, Bi, Tl) are generally correlated with higher Tc,max in experiments. We then show the underlying fundamental phenomena of coupled apical charge flux and lattice dynamics when the apical oxygen oscillates vertically. This triggers the charge flux among the apical cation, apical anion, and the in-plane CuO4 unit. The effect not only dynamically modulates the site energy of the hole at a given Cu site to control the in-plane charge transfer energy, but also can modulate the in-plane hole hopping integral simultaneously in a dynamic way by the cooperative apical charge fluxes.

Harvard SEAS news report: The culprit of superconductivity in cuprates


2. A new picutre of pseudogap phase in cuprate superconductors is described in the unique langurage of charge fluxes. Due to these ultrafast fluxes, fundamental excitation in cuprates is redefined as pQon with internal structures, where p-state and Q-state can dynamically convert between each other with a momentum dependence. npj Computational Materials

flux confiement