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During the last years we have witnessed colossal advancements in all-electrical doping control on
cuprates. In the vast majority of cases, the tuning of charge carrier density has been achieved via electric field effect by means of either a ferroelectric polarization or by using a dielectric or electrolyte gating. Unfortunately, these approaches are constrained to rather thin superconducting layers and require large electric fields in order to ensure sizable carrier modulations [1, 2]. In this master thesis, we focus on the investigation of oxygen doping in an extended region through current-stimulated oxygen migration in Y B a 2 Cu 3 O 7−δ superconducting bridges. The underlying methodology is rather simple and avoiding sophisticated overlay nanofabrication process steps and complex electronics. A patterned 
multiterminal transport bridge configuration allows us to electrically assess the directional counterflow of oxygen atoms and vacancies. Importantly, the emerging propagating front of current-dependent doping δ isprobed in situ by polarized optical microscopy and scanning electron microscopy. The resulting imaging techniques, together with photo-induced conductivity and Raman scattering investigations reveal an inhomogeneous oxygen vacancy distribution with a controllable propagation speed permitting us to estimate the oxygen diffusivity. These findings provide direct evidence that the microscopic mechanism at play in electrical doping in cuprates involves diffusion of oxygen atoms with the applied current. The resulting fine control of the oxygen content in complex oxides paves the way towards a systematic study of complex phase diagrams and the design of electrically addressable devices.

superconductivity --- ybco --- high temperature superconductors --- electromigration --- photoconductivity --- cuprate superconductivity --- Physique, chimie, mathématiques & sciences de la terre > Physique --- Physique, chimie, mathématiques & sciences de la terre > Chimie

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Throughout the history of materials science and physics, few topics have captured as much interest as the phenomenon of superconductivity (SPC), discovered in 1911. Perhaps this is because of the intriguing interpretation of the phenomenon, which remains controversial, or for the secret hope of being able to synthesize a material with a critical superconductive transition temperature (TC) high enough to revolutionize the sector of energy generation and transport. As a matter of fact, the search for new superconductor materials has motivated an army of scientists, in particular, after the discovery of high-TC superconductor cuprates (HTS) in the mid-80s. Besides the unremitting interest in HTS, new materials, such as intermetallic borides, iron–nickel-based superconductors, heavy fermion, and organic and superhydride systems, are still delivering outstanding achievements to the scientific community, among which includes thousands of papers and a handful of Nobel prize winners). This Special Issue “Synthesis and Characterization of New Superconductor Materials” is a collection of scientific contributions providing new insights and advances in this fascinating field, addressing issues ranging from the fundamental research (theory and correlation between critical temperature, TC, and structural properties) to the development of innovative solutions for practical applications of superconductivity: Synthesis of new superconducting materials Magnetic and/or electric characterization of the TC transition Role of crystal symmetry and chemical substitutions on TC TC dependence on external stimuli and/or non-ambient conditions Theoretical modeling

Dirac electron --- Landau level --- interlayer magnetoresistance --- organic conductor --- α-(BEDT-TTF)2I3 --- Er123 --- melt temperature --- superconducting solder --- superconducting joint --- FeSe --- superconductivity --- high pressure --- chemical intercalation --- interfacial coupling --- AC susceptibility --- BaZrO3 --- co-precipitation --- solid-state --- YBa2Cu3O7−δ --- Weyl semimetal --- focused ion beam --- high-temperature superconductors --- bismuth-based cuprates --- Bi-2212 --- n/a