Combined microwave and Eliashberg analysis of the effects of disorder in Iron Based Superconductors
| Date/Time: | Thursday, 31 Jan 2019 from 4:10 pm to 5:00 pm |
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| Location: | Physics 3 |
| Phone: | 515-294-7377 |
| Channel: | College of Liberal Arts and Sciences |
| Actions: | Download iCal/vCal | Email Reminder |
In this seminar I will present a combined experimental and theoretical approach toward reaching new insights into the mechanisms of superconductivity through the analysis of the effects of disorder in Iron Based Superconductors (IBS). We investigate the critical temperature, penetration depth, quasiparticle conductivity and surface impedance of high-quality IBS single crystals by a planar waveguide resonator technique, in a cavity perturbation approach. The experimental method and data analysis are described, showing that this technique is reliable for the study of small crystals and, since the measurement technique is non-destructive and does not alter the crystals, the very same samples can be measured before and after irradiation, making the analysis of the effects of additional defects more reliable. The absolute values of the penetration depth are accessible by the experiment, showing a fairly good agreement with literature data.The experimental data is compared to calculations based on the Eliashberg equations within the s+- wavemodel, giving a remarkable agreement. This overall consistency validates the model itself, thus allowing us to estimate parameters that are missing in literature. The calculations are also able to explain in a consistent way the effects of disorder both on the critical temperature and on penetration depth, by suitably accounting for the impurity scattering due to the defects created by irradiation. This combined approach has allowed the identification of the disorder induced s+- to s++ order parameter symmetry transition in Rh-doped crystals.