# Proximity effects

Another area where technological advances have been key to recent progress is the study of multi-layered materials and nano-structures.

An important phenomenon in this area is the proximity effect, by which an ordered state of a given material (e.g. magnetism or superconductivity) leaks into an adjacent one over some finite length scale ξ.

The development of photo-doping techniques and increasingly refined molecular beam epitaxy led to the observation, in the first half of the present decade, of giant proximity effects between differently-doped high-temperature superconductors.

The theory of such giant proximity effects is another area where the ISIS theory group is making active contributions, in close collaboration with experimentalists. This has important implications not only in the field of superconductivity, but also for magnetic devices (spintronics).

**References:**

- J. Quintanilla, K. Capelle, L.N. Oliveira,

*Density-functional description of superconducting and magnetic proximity effects across a tunneling barrier,*

Phys. Rev. B 78, 205426 (2008). - J. Quintanilla, K. Capelle, L.N. Oliveira,

*Comment on "Anomalous proximity effect in underdoped YBa*_{2}Cu_{3}O_{6+x} Josephson junctions",

Phys. Rev. Lett. 90, 089703 (2003).