Two distinct superconducting phases in LiFeAs.
A non-trivial temperature evolution of superconductivity including a temperature-induced phase transition between two superconducting phases or even a time-reversal symmetry breaking order parameter is in principle expected in multiband superconductors such as iron-pnictides. Here we present scanning tunnelling spectroscopy data of LiFeAs which reveal two distinct superconducting phases: at = 18 K a partial superconducting gap opens, evidenced by subtle, yet clear features in the tunnelling spectra, i.e. particle-hole symmetric coherence peak and dip-hump structures. At Tc = 16 K, these features substantiate dramatically and become characteristic of full superconductivity. Remarkably, the distance between the dip-hump structures and the coherence peaks remains practically constant in the whole temperature regimeT ≤ . This rules out the connection of the dip-hump structures to an antiferromagnetic spin resonance.
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.
P K
PK
Nag
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.
R
R
Schlegel
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.
D
D
Baumann
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.
H-J
HJ
Grafe
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.
R
R
Beck
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.|Institute for Solid State Physics, TU Dresden, 01069 Dresden, Germany.
S
S
Wurmehl
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.|Institute for Solid State Physics, TU Dresden, 01069 Dresden, Germany.|Center for Transport and Devices, TU Dresden, 01069 Dresden, Germany.
B
B
Büchner
IFW Dresden, Institute for Solid State Research, 01171 Dresden, Germany.|Center for Transport and Devices, TU Dresden, 01069 Dresden, Germany.
C
C
Hess