Choose timezone
Your profile timezone:
Powered by Indico
v3.3.5
Superlattices, i.e. quasiperiodic multilayered structures, have become an essential part of modern microelectronics. So far superlattice devices, such as the Quantum Cascade Laser, relied on a complicated fabrication of artificial semiconductor heterostructures. However, nature provides us with a large family of layered compounds in which the superlattice structure is inherent at the atomic level. In many of those compounds mobile charge carriers are localized in atomic planes, while the interlayer transport is achieved via tunneling. Single crystals of such materials represent stacks of atomic scale “intrinsic” tunnel junctions with a stacking periodicity determined by the crystallographic structure. The low-dimensional electronic structure is responsible for unusual physical properties of those compounds, including among others colossal magnetoresistance (e.g., LaSrMnO manganites), charge or spin density wave ordering (e.g., transition metal chalcogenides and various organic metals), and high temperature superconductivity (HTS) (e.g., Bi- and Tl- cuprates). At present evidence for tunneling nature of interlayer transport was obtained for Bi- and Tl-based HTS , NbSe_3 and LaSe-NbSe_2 compounds , organic superconductor k-(BEDT-TTF)_2 Cu (NCS)_2 , magnetic LaSrMnO manganites and magnetic superconductor RuSrGdCuO.
Intrinsic tunnel junctions are indispensable for fundamental studies of layered materials, e.g., provide a unique opportunity to probe bulk electronic spectra of high Tc superconductors. On the other hand, unusual properties of intrinsic junctions open a possibility for constructing novel electronic devices at the ultimate atomic scale.