High-temperature interface superconductivity between metallic and insulating copper oxides

Abstract

The realization of high-transition-temperature (high-T(c)) superconductivity confined to nanometre-sized interfaces has been a long-standing goal because of potential applications and the opportunity to study quantum phenomena in reduced dimensions. This has been, however, a challenging target: in conventional metals, the high electron density restricts interface effects (such as carrier depletion or accumulation) to a region much narrower than the coherence length, which is the scale necessary for superconductivity to occur. By contrast, in copper oxides the carrier density is low whereas T(c) is high and the coherence length very short, which provides an opportunity-but at a price: the interface must be atomically perfect. Here we report superconductivity in bilayers consisting of an insulator (La(2)CuO(4)) and a metal (La(1.55)Sr(0.45)CuO(4)), neither of which is superconducting in isolation. In these bilayers, T(c) is either approximately 15 K or approximately 30 K, depending on the layering sequence. This highly robust phenomenon is confined within 2-3 nm of the interface. If such a bilayer is exposed to ozone, T(c) exceeds 50 K, and this enhanced superconductivity is also shown to originate from an interface layer about 1-2 unit cells thick. Enhancement of T(c) in bilayer systems was observed previously but the essential role of the interface was not recognized at the time.

Superconductivity above 100 K in single-layer FeSe films on doped SrTiO3

“…During this experiment, the thermometer reads 295.7 K at room temperature and 77.6 K when immersed in the liquid nitrogen. Given that the thermometer is thermally anchored at the sample stage that is thermally linked to liquid 4 He or N 2 bath and the film sits on top of the substrate, the sample temperature cannot be lower than the cold stage temperature measured by the thermometer. …”

“…with the earlier work on superconducting oxides interfaces [3][4][5][6] , demonstrates that interface between two different materials provide not only a rich system for studying two-dimensional (2D) superconductivity, but also a potential pathway to high-T c superconductivity [7][8][9][10][11][12] .…”

Nonvolatile Resistive Switching inPt/LaAlO3/SrTiO3Heterostructures

“…Heterostructures of perovskite oxides are emerging as one of the most fascinating systems in condensed-matter physics, exhibiting a wide range of properties [1], such as the two-dimensional electron gas [2][3][4], orbital reconstruction [5,6], interfacial superconductivity [7,8], ferromagnetism [9][10][11], and enhanced capacitance [12]. In particular, the discovery of high-mobility conduction at the interface between two insulators LaAlO 3 (LAO) and SrTiO 3 (STO) has launched intensive experimental and theoretical investigations on the physics and applications of this novel strong correlated electronic state [2][3][4]13,14].…”

Interface superconductivity

“…Extensive studies of bilayer structures made of underdoped (insulating-I) and overdoped (metallic-M and non-superconducting) (La 1−x Sr x )CuO 4 have been performed by the group of Ivan Bozovic in Brookhaven and also in Bremen [80,81].…”