Electron transport in nanostructures: the key to high temperature superconductivity |
Hans-Peter Roeser |
University of Stuttgart Institute of Space Systems (IRS), Pfaffenwaldring 31, Stuttgart 70569, Germany |
Abstract |
The electron transport in nanostructured Schottky barrier diodes - used as low noise THz mixers up to 5 THz – is ballistic. Best signal-to-noise performance is achieved when the phase coherent electron movement is characterized by an optimum barrier depletion thickness D_{depl} which has the thickness of twice the doping distance D_{depl} = 2x. Detailed investigations on different Schottky diodes show a linear relation between (2x)^{2} and the mobility µ of the device: (2x)^{2} = h/2e • µ. Since the mobility µ is proportional to (energy)^{-1} and because of many similarities compared to high temperature superconductors (HTSC) it has been investigated if the doping distance in HTSCs is connected with (kT_{c})^{-1}. By analysing published data of very well studied HTSCs we found out that P-type as well as N-type HTSCs with single (n = 1) and multilayered superconducting CuO_{2} layers and even recently discovered iron-arsen based HTSCs show a linear correlation between the doping distance x and the critical transition temperature T_{c}. It turns out that the correlation equation (2x)^{2} • n^{-2/3} • 2M_{eff} • πkT_{c} = h^{2} can be derived theoretically from the density of states in a one-dimensional quantum wire. This suggests that the superconducting CuO_{2} plane consists of superconducting quantum wires. The correlation equation has the prospect to calculate the transition temperature for HTSCs for the first time. The paper will describe the electron transport phenomena in nanostructured Schottky diodes in the THz range and the detailed investigation of the different HTSC families. |
Presentation: Keynote lecture at E-MRS Fall Meeting 2009, Symposium D, by Hans-Peter Roeser Submitted: 2009-05-10 17:33 Revised: 2009-08-13 17:31 |