Ultra-high Critical Current Densities of Superconducting YBa2Cu3O7-d thin Films in the Overdoped State

Abstract

Doping is one of the most relevant paths to tune the functionality of cuprates, it determines carrier density and the overall physical properties of these superconducting materials. We present an oxygen doping study of YBa2Cu3O7-d (YBCO) thin films from underdoped to overdoped state, correlating the measured charge carrier density, nH, the hole doping, p, and the critical current density, Jc. Our results show experimental demonstration of a linear correlation between Jc and nH, up to Quantum Critical Point (QCP), due to an increase of the superconducting condensation energy. The ultra-high Jc achieved, 90 MA cm-2 at 5 K corresponds to a third of the depairing current, i.e. a value 60 % higher than ever reported in YBCO films. The overdoped regime is confirmed by a sudden increase of nH, associated to the reconstruction of the Fermi-surface at the QCP. Overdoping YBCO opens a promising route to extend the current carrying capabilities of REBCO coated conductors for applications.

Thermodynamic approach for enhancing superconducting critical current performance

“…Further insight into the effects of the combination of increasing Jd and enhancing flux pinning can be obtained from the field dependence of Jc. Compared with overdoped standard Y123 at 5 K [16], the enhancement of our overdoped (Y,Gd)123+BHO CC is 144% at self-field and 199% at 5 T. Moreover, compared to that in coherent BHO doped CCs [59], the Jc(H||c) of our CC shows a 254% increase at 1 T and 175% increase at 18…”

“…, where the pinning force, Fp= Jc(H)0H is compared with that of several RE123 materials [16,[57][58][59]. The Fp at 4.2 K of our overdoped (Y,Gd)123+BHO CC reaches ~ 3.17 TN/m 3 at 18 T (H||c), which is the highest reported value for any superconductor material.…”

“…(a) Jc(H||c) at 4.2 K and (b) Fp-0H curve of overdoped (Y,Gd)123+BHO CCs at 4.2 K and H||c. For comparison, the data for Sm123+coherent BHO film [57], (Y,Gd)123+coherent BZO CC [58], (Y,Gd)123+coherent BHO CC [59], overdoped Y123 film at 5 K [16], and Y123 CCs [58] are included.…”

“…Experimentally, the enhancement of Jc by tuning the carrier density, especially in standard RE123 films, i.e. without artificial pinning centers (APCs), has been reported [14][15][16]. Recently, A. Stangl et al reported that overdoped standard Y123 films grown by Pulsed Laser Deposition (PLD) reached 18% of Jd at 5 K, which is a consequence of the increase of the condensation energy with charge carrier density [17].…”

Superconducting Vortex-Charge Measurement Using Cavity Electromechanics

“…The radial profiles of the local magnetic field and the normalized critical current are shown in Figure 3b. For these calculations, we have used the critical current density of J c0 = 3680 A/μm 35,36 and B 0 = 100 mT. 37 Additional details of the model are included in the Supporting Information.…”