Bamboo-like Vortex Chains Confined in Canals with Suppressed Superconductivity and Standing Waves of Quasiparticles

Abstract

The vortex core can be regarded as a nanoscale confined system for quasiparticles in a type-II superconductor. It is very interesting to investigate the interplay between the vortex core and other microscopic quantum confined systems. We observe band-like canals with the width of about 15 nm on the surface of KCa2(Fe1–x Ni x )4As4F2 (x = 0.05) by scanning tunneling microscopy. Some canals suppress superconductivity and confine parallel standing waves due to the quasiparticle interference. Upon magnetic fields being applied, some elongated vortices are formed within canals showing bamboo-like one-dimensional vortex chains. Interestingly, the confined vortex cores are elongated roughly along the perpendicular direction of canals, and the local density of states at positive and negative energies shows an in-phase oscillation at zero field; but, it becomes out-of-phase crossing the vortex cores. Our work reveals a new type of vortex patterns in confined canals and its interplay with the quasiparticle interference.

Influences of quenching treatment and cobalt-doping on the thermally activated flux-flow behavior in KCa2(Fe 1−x Co x )4As4F2

“…The second magnetization peak were revealed both in the RbCa 2 Fe 4 As 4 F 2 and KCa 2 Fe 4 As 4 F 2 systems by the magnetization measurements [22][23][24]. Recent scanning tunneling microscopy measurements have revealed the Friedel oscillations of vortex bound states and a new type of vortex pattern with bamboo-like chains in confined canals in the KCa 2 Fe 4 As 4 F 2 compound [25,26]. In addition, we have observed a significant suppression of the activation energy for the flux flow in the ultra-thin sample of KCa 2 Fe 4 As 4 F 2 [12].…”