Disorder-controlled superconductivity at YBa2Cu3O7/SrTiO

Javier García‐Barriocanal

¹

,

A. Pérez-Muñoz

²

,

Z. Sefrioui

³

et al.

Abstract

We examine the effect of interface disorder in suppressing superconductivity in coherently grown ultrathin YBa 2 Cu 3 O 7 (YBCO) layers on SrTiO 3 (STO) in YBCO/STO superlattices. The termination plane of the STO is TiO 2 and the CuO chains are missing at the interface. Disorder (steps) at the STO interface cause alterations of the stacking sequence of the intracell YBCO atomic layers. Stacking faults give rise to antiphase boundaries which break the continuity of the CuO 2 planes and depress superconductivity. We show that superconductivity is directly controlled by interface disorder outlining the importance of pair breaking and localization by disorder in ultrathin layers. Complex oxide interfaces in epitaxial heterostructures have become a very active research area. The thrust of this rapidly expanding field comes partly from the plethora of novel effects and physical phenomena discovered in oxide superlattices and partly by an exciting horizon of novel devices and applications. The electronic reconstruction taking place at these interfaces is known to have important effects triggering modifications of fundamental electronic parameters such as charge density, on site Coulomb interaction and bandwidth giving rise to stabilization of novel electronic ground states with emerging properties.1,2 Apart from its fundamental interest, the possibility of tailoring the electronic structure of the interfaces to display novel behaviors and functionalities may open interesting pathways in device design for oxide electronics. Although progress has been made in achieving atomic precision of the interface growth, epitaxial strain, intermixing, or more sophisticated electronic processes related to the polar nature of complex oxides play a role in generating chemical or physical disorder, which may cause profound changes in the free carrier density or other physical quantities controlling the equilibrium between phases.Devices based on oxide-oxide interfaces, including Schottky and p-n junctions 3-6 and field-effect transistors (FETs) 7,8 are being extensively investigated. Significant progress has been achieved in the field-effect control of the carrier density of a superconducting cuprate using a FET device 9 and more recently using electric double layer (EDL) techniques.10 Electrostatic doping constitutes an alternative to chemical doping with the advantage of not introducing the disorder associated to element substitution. However, in FET devices there is an inherent class of disorder related to an unavoidable presence of an interface which may also deeply influence the doping process. The modulation of the charge density occurs within the Thomas-Fermi screening length, typically of the order of 1 nm. Electrostatic doping is an interfacial phenomenon, and may be influenced by the kinds of interface effects such as strain, charge transfer, polarity mismatch, etc. Moreover, the two-dimensional (2D) character of the cuprate makes its normal and superconducting states especially sensitive to disorder and localization effects ...

Suppression of superconductivity at the nanoscale in chemical solution derived YBa2Cu3O7−δthin films with defective Y2Ba4Cu8O16intergrowths

“…It is noteworthy that T c gradually decreases down to 50 nm lm thickness, followed by a sudden drop at lower thicknesses. Similar behaviors have also been observed in vacuum deposited Y123 lms 47,56 or strained superlattices, 54,61 even if the observed T c decrease is more severe in the present case. We should note, as well, the obvious increase of DT c which is very likely inuenced by a decrease of the shielding efficiency of the percolating currents at smaller lm thickness.…”

Colloquium: Emergent properties in plane view: Strong correlations at oxide interfaces

“…Additional issues beyond conceptual approaches to interface control arise. The length scales in correlated oxides are typically very short, so the details of the interface may be more important than in conventional semiconductors.A local picture is needed, which is able to address the formation of chemical bonds across the junction, differing elec-tronegativities of transition metal ions, changes in both crystal field energies and Madelung potentials, and polarity effects (Biscaras et al, 2012;Garcia-Barriocanal et al, 2013;Herranz et al, 2007;Hotta et al, 2007;Ohtomo and Hwang, 2004;Park et al, 2013b;Salluzzo et al, 2013;Savoia et al, 2009;Sing et al, 2009;Takizawa et al, 2009;Zhong et al, 2010).…”

Superconductor–Insulator Transitions in Exfoliated Bi2Sr2CaCu2O8+δ Flakes

“…Understanding the emergence of these phases and their competition/coexistence with superconductivity is of vital importance, as it may shed light on the mechanism for the high transition temperature of the cuprate superconductors. Of late, ionic liquid gating has been proven especially effective in modulating the charge carrier density 3,4 , switching the cuprates between a superconductor and an insulator [5][6][7][8][9] . SIT has been realized in both hole-doped (La2−xSrxCuO4 5 , YBaCu3O7−x 6 , La2CuO4+δ 8 ) and electron-doped (Pr2−xCexCuO4 9 ) cuprates with the superconducting block of only 1 to 4 unit cells.…”