Description:

Nanostructure and microfabrication techniques have been invaluable for unraveling physics in metals and semiconductors, since they enable patterning and electronic probes on physically interesting length scales. At the same time, there remains much interest in understanding so-called correlated materials, systems in which strong electron-electron and electron-phonon interactions lead to rich phenomenology associated with competing ordered states, such as magnetism, superconductivity, etc. I will present two examples of using nanostructures incorporating correlated materials to reveal new physical insights. We have examined electronic transport in crystals of V5S8, an antiferromagnetic metal that is better considered as V(0.25)VS2, down to nanoscale thicknesses. These measurements reveal a previously unrecognized metamagnetic transition, and indicate that this system undergoes a quantum phase transition as a function of field. Very recently, we have been examining epitaxially grown tunnel junctions consisting of La(2-x)Sr(x)CuO4 high temperature superconductor layers separated by a tunnel barrier of the undoped, antiferromagnetic Mott insulating parent compound La2CuO4. In addition to measuring tunneling spectra, I will discuss our measurements of shot noise in the tunneling current, both above and below Tc, for several dopings. Shot noise effectively measures the magnitude of the charge of the tunneling carriers. The results of these measurements will be discussed in the context of other experiments seeking to understand the enigmatic normal state of the cuprates.

Professor Doug Natelson, Rice University

Host: Venkat Chandrasekhar

Keywords: Physics, Astronomy, Condensed Matter