Interfacial-Redox-Induced Tuning of Superconductivity in YBa₂Cu₃O_7-δ

Abstract

Solid-state ionic approaches for modifying ion distributions in getter/oxide heterostructures offer exciting potentials to control material properties. Here, we report a simple, scalable approach allowing for manipulation of the superconducting transition in optimally doped YBa2Cu3O7‑δ (YBCO) films via a chemically driven ionic migration mechanism. Using a thin Gd capping layer of up to 20 nm deposited onto 100 nm thick epitaxial YBCO films, oxygen is found to leach from deep within the YBCO. Progressive reduction of the superconducting transition is observed, with complete suppression possible for a sufficiently thick Gd layer. These effects arise from the combined impact of redox-driven electron doping and modification of the YBCO microstructure due to oxygen migration and depletion. This work demonstrates an effective step toward total ionic tuning of superconductivity in oxides, an interface-induced effect that goes well into the quasi-bulk regime, opening-up possibilities for electric field manipulation.

Electrically Enhanced Exchange Bias via Solid-State Magneto-ionics

“…The first occurs upon the Gd layer deposition, resulting in a chemically induced redox reaction that strips oxygen from the adjacent NiCoO and leaves behind the FM NiCo observed in the magnetometry, PNR, and STEM of the as-grown samples. The resultant valence change at the interface is similar to those reported earlier. , More disorder is induced at the NiCoO top surface after the Gd deposition (Supporting Information Figure S5). This gadolinium oxidation process is exothermic, with a change in enthalpy Δ H of −11.4 eV per molecule of Gd 2 O 3 formed [3­(Ni, Co)O + 2Gd → 3­(Ni, Co) + Gd 2 O 3 ] .…”

“…The resultant valence change at the interface is similar to those reported earlier. 21,24 More disorder is induced at the NiCoO top surface after the Gd deposition (Supporting Information Figure S5). This gadolinium oxidation process is exothermic, with a change in enthalpy ΔH of −11.4 eV per molecule of 50 Thus, local heating may help to increase ionic mobility in the surrounding region, although the degree to which this feedback effect enhances the redox reaction is difficult to quantify due to the inhomogeneity of the interface.…”

Cation and anion topotactic transformations in cobaltite thin films leading to Ruddlesden-Popper phases

“…As a result, these structural changes lead to substantial modification to the physical properties. demonstrated in several complex oxide systems, including La0.7Sr0.3CoO3, [13,14] La0.67Sr0.33MnO3, [15] and YBa2Cu3O7-δ, [16] by the deposition of ultrathin Gd layers of varying thickness. The Gd getter layer experienced a spontaneous redox reaction to form GdOx, leaching oxygen ions from the underlying complex oxide thin films and resulting in a topotactic transformation, which then leads to a change in the magnetic and electrical properties in these complex oxides.…”

Controlled Sign Reversal of Electroresistance in Oxide Tunnel Junctions by Electrochemical-Ferroelectric Coupling

“…Oxygen vacancies, however, are defects difficult to detect and in many cases also to avoid in these oxides [2], and may have drastic effects on materials properties through their associated strain and doping fields [3]. In oxide nanostructures, defect formation energy may be substantially reduced, and as a result, oxygen vacancies can be generated under the action of external electric fields and accumulate at boundaries enabling the modification of their electrochemical state [4][5][6]. Recently, coupling between electrochemical and ferroelectric states has been found at surfaces of ultrathin ferroelectric layers [7].…”