Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures

Abstract

The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leading to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates.

Properties of LSMO/YBCO cross-strip type junctions

“…The second effect that should be taken into account is the charge transfer through the CMR/HTS interface ranging in distance from a few tenths of nm to several nm [7,8,9]. Gray et al [7] found a loss of 0.67 electrons per CMR monolayer in their CMR/HTS superlattices, which leads to conversion of the CMR layer to a paramagnetic or antiferromagnetic insulator.…”

“…Gray et al [7] found a loss of 0.67 electrons per CMR monolayer in their CMR/HTS superlattices, which leads to conversion of the CMR layer to a paramagnetic or antiferromagnetic insulator. On the other hand, the electrons transferred through the CMR/HTS interface dope the Cu and Ba atoms in the YBCO and transform the superconducting YBCO to a Mott insulator.…”

“…Therefore, such materials, and especially the CMR/HTS interface, are attractive for studying the interplay between two fundamental condensed-matter phenomena, superconductivity (S) and ferromagnetism (F). Recent developments in fabricating atomically smooth (flat) CMR/HTS interfaces in superlattices [1,2] provided an ideal system to investigate intriguing phenomena, such as a long-range proximity effect [3,4], spinpolarized quasiparticle injection into the HTS layer within a spin-diffusion length  FM [5], giant modulation of the CMR-layer magnetization induced by superconductivity [6], or charge transfer from CMR into HTS [7,8,9]. A variety of effects and phenomena at the SF interface offer possibilities of using these materials in different microelectronic and spintronic applications [10].…”

High-spin state and magnetic coupling induced through interfacial orbital reconstruction observed in SrRuO3/LaNiO3superlattice

“…and single layer SRO (1,2,4,8,12,20 u.c.) and LNO (1,2,4,8,12,20 u.c.) reference samples were grown on STO (001) substrates by pulsed laser deposition.…”

“…The electronic structure at the perovskite-oxide interface between two transition metal oxides features complex interactions among the lattice, charge, spin, and orbital degrees of freedom and shows many emergent physical properties, including high-temperature superconductivity [1], magnetoresistance [2], exchange bias (EB) [3], and ferroelectricity [4]. With regard to these complex oxide structures, many of which are epitaxially compatible, the past decade has seen rapid growth in materials science at the atomic level with the creation of heterostructures with unique properties [5].…”