Regensburg 2016 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 25: Superconductivity: Fe-based Superconductors - 1111 & 111
TT 25.3: Talk
Tuesday, March 8, 2016, 10:00–10:15, H19
Unusual temperature evolution of superconductivity in LiFeAs — •Pranab Kumar Nag1, Ronny Schlegel1, Danny Baumann1, Hans-Joachim Grafe1, Robert Beck1, Sabine Wurmehl1,2, Bernd Büchner1,2,3, and Christian Hess1,3 — 1Leibniz-Institute for Solid State and Materials Research, IFW-Dresden, 01069 Dresden, Germany — 2Institute for Solid State Physics, TU Dresden, 01069 Dresden — 3Center for Transport and Devices, TU Dresden, 01069 Dresden, Germany
We have performed temperature dependent scanning tunneling spectroscopy on an impurity-free surface area of a LiFeAs single crystal [1]. Our data reveal a highly unusual temperature evolution of superconductivity: at Tc*=18 K a partial superconducting gap opens, as is evidenced by subtle, yet clear features in the tunneling spectra, i.e. particle-hole symmetric coherence peaks and dip-hump structures. At Tc=16 K, these features substantiate dramatically and become characteristic of full superconductivity. Remarkably, this is accompanied by an almost jump-like increase of the gap energy at Tc to about 87% of its low-temperature gap value. The energy of the dip as measured by its distance to the coherence peak remains practically constant in the whole temperature regime T≤ Tc*. We compare these findings with established experimental and theoretical results.
P. K. Nag et al., arXiv:1509.03431(2015)