In LaAlO3/SrTiO3 heterostructures, a still poorly understood phenomenon is that of electron trapping in back-gating experiments. Here, by combining magnetotransport measurements and self-consistent... Show moreIn LaAlO3/SrTiO3 heterostructures, a still poorly understood phenomenon is that of electron trapping in back-gating experiments. Here, by combining magnetotransport measurements and self-consistent Schrödinger-Poisson calculations, we obtain an empirical relation between the amount of trapped electrons and the gate voltage. The amount of trapped electrons decays exponentially away from the interface. However, contrary to earlier observations, we find that the Fermi level remains well within the quantum well. The enhanced trapping of electrons induced by the gate voltage can therefore not be explained by a thermal escape mechanism. Further gate sweeping experiments strengthen that conclusion. We propose a new mechanism which involves the electromigration and clustering of oxygen vacancies in SrTiO3 and argue that such electron trapping is a universal phenomenon in SrTiO3-based two-dimensional electron systems. Show less
Giesbers, J.M.; Uhlírová, K.; Konecny, M.; Peters, E.C.; Burghard, M.; Aarts, J.; Flipse, C.F.J. 2013
A comparison was made between four low-temperature properties of LaCu2Si2 and CeCu2Si2. Whereas LaCu2Si2 behaves like a normal metal, CeCu2Si2 shows (i) low-temperature anomalies typical of ... Show moreA comparison was made between four low-temperature properties of LaCu2Si2 and CeCu2Si2. Whereas LaCu2Si2 behaves like a normal metal, CeCu2Si2 shows (i) low-temperature anomalies typical of "unstable 4f shell" behavior and (ii) a transition into a superconducting state at Tc≃0.5 K. Our experiments demonstrate for the first time that superconductivity can exist in a metal in which many-body interactions, probably magnetic in origin, have strongly renormalized the properties of the conduction-electron gas. Show less
