### Session G38: Focus Session: Superconductivity-Carbon Alloying of Magnesium Diboride and Related Compounds

8:00 AM–11:00 AM, Tuesday, March 14, 2006
Baltimore Convention Center Room: 341

Chair: Paul Canfield, Iowa State University

Abstract ID: BAPS.2006.MAR.G38.1

### Abstract: G38.00001 : Tuning the Superconducting Properties of MgB$_{2}$

8:00 AM–8:36 AM

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#### Author:

Rudeger H.T. Wilke
(University of Wollongong)

The relatively high superconducting transition temperature of 39 K in MgB$_{2}$ has garnered much interest over the past several years in both fundamental and applied research. MgB$_{2}$ is a conventional phonon mediated BCS superconductor with the unconventional property of two superconducting gaps. These gaps ($\sigma$ and $\pi )$ arise from the coupling of boron phonons with two different orthogonal sheets of the Fermi surface. In a conventional single gap superconductor the upper critical field can be tuned by the introduction of nonmagnetic impurities. For MgB$_{2}$ the situation becomes more complex because there are 3 important scattering channels (inter and intra-band). Theoretical calculations predict different developments of the upper critical field and anisotropy ratio if the scattering can be selectively tuned to a specific channel. In this talk I will present data on two different types of perturbations to MgB$_{2}$: carbon doping and neutron irradiation. Low level carbon doping enhances the upper critical field with only a minor decrease in T$_{c}$. Whereas T$_{c}$ suppression is the result of carbon electron doping the system, the enhancement of H$_{c2}$(T=0) is the result of an increase in scattering, with evidence to suggest carbon doping enhances intra-$\pi$-band scattering. In contrast, H$_{c2}$(T=0) values tend to scale with T$_{c}$ in heavily neutron irradiated samples and the superconducting properties can be understood in terms of a decrease in the density of states at the Fermi surface and an increase in interband scattering.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.G38.1