Visualizing pair formation on the atomic scale in the high-Tc superconductor Bi2Sr2CaCu2O8+d

Understand

Pairing of electrons in conventional superconductors occurs at the superconducting transition temperature Tc, creating an energy gap D in the electronic density of states (DOS).

• In the high-Tc superconductors, a partial gap in the DOS exists for a range of temperatures above Tc.
• A key question is whether the gap in the DOS above Tc is associated with pairing, and what determines the temperature at which incoherent pairs form.
• Here we report the first spatially resolved measurements of gap formation in a high-Tc superconductor, measured on Bi2Sr2CaCu2O8+d samples with different Tc values (hole concentration of 0.12 to 0.22) using scanning tunnelling microscopy.