Measurement of the Superfluid Density and other Electronic Properties of Electron-Doped Cuprate Superconductors

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

This project focuses on electronic properties of CuO(2) planes in electron-doped cuprates, e.g., Pr(2-x)Ce(x)CuO(4) and La(2-x)Ce(x)CuO(4), in comparison with hole-doped cuprates, especially the closely-related compound La(2-x)Sr(x)CuO(4). At issue is the nature of the superconducting state in e-doped cuprates, and whether there is a transition in pairing symmetry near optimal doping. The project will provide the first measurements of two quantities of fundamental importance. One is the magnitude and temperature dependence of the superfluid density, which is proportional to the inverse square of the magnetic penetration depth. The penetration depth will be measured from 0.5 K up to the superconducting transition temperature in samples spanning a wide doping range, x. Another is the electronic heat capacity anomaly at the superconducting transition. Supporting measurements of normal-state transport, e.g., resistivity and Hall coefficient will also be made. Research will provide excellent training in state-of-the-art experimental techniques to graduate and undergraduate students. This project benefits from a collaboration with the world's premier maker of electron doped cuprate films, Dr. Michio Naito of NTT, Japan. A central issue in condensed matter physics and in materials science is identification of microscopic mechanisms that enable electrons to move within a solid, rather than being attached to a particular atom. The present project focuses on understanding electrons that move within copper-oxide planes in a class of superconducting compounds that includes Pr(2-x)Ce(x)CuO(4) and La(2-x)Ce(x)CuO(4). Superconductivity in these copper-oxide compounds has been the subject of intense international research efforts since their discovery in 1986. The main question now is whether the superconducting state in these compounds is the same as found in a very similar compound, La(2-x)Sr(x)CuO(4). To illuminate this issue, the project will provide measurements of the magnitudes and temperature dependencies of quantities of fundamental importance, namely, the density of superconducting electrons, and the contribution of superconducting electrons to the heat capacity at the transition into the superconducting state. The research will provide excellent training in state-of-the-art experimental techniques to graduate and undergraduate students.