0000000000435920
AUTHOR
Samuel Mañas Valero
Two-Dimensional Crystals and van der Waals Heterostructures based on Inorganic and Molecular Strongly Correlated Layered Materials
“En resumen, toda obra grande es el fruto de la paciencia y de la perseverancia, combinadas con una atención orientada tenazmente durante meses y aun años hacia un objeto particular”. “In summary, all great work is the fruit of patience and perseverance, combined with tenacious concentration on a subject over a period of months or years”. Santiago Ramón y Cajal (Reglas y consejos sobre investigación científica. Madrid: Academia de Ciencias Exactas, Físicas y Naturales, 1897). The present Thesis constitutes a journey –a romance of many dimensions, quoting Edwin Abbot Abbot– from 3D to 2D and, hopefully (we let the curious Reader judge), “Through Flatland to Thoughtland” (citing, again, Abbot…
Low-Frequency Imaginary Impedance at the Superconducting Transition of 2H-NbSe2
The superconducting transition leads to a sharp resistance drop in a temperature interval that can be a small fraction of the critical temperature T$_c$. A superconductor exactly at T$_c$ is thus very sensitive to all kinds of thermal perturbations, including the heat dissipated by the measurement current. We show that the interaction between electrical and thermal currents leads to a sizeable imaginary impedance at frequencies of order of tens of Hz at the resistive transition of single crystals of the layered material 2H-NbSe$_2$. We explain the result using models developed for transition edge sensors. By measuring under magnetic fields and at high currents, we find that the imaginary im…
Path to Overcome Material and Fundamental Obstacles in Spin Valves Based on MoS2 and Other Transition-Metal Dichalcogenides
Experimental studies on spin valves with exfoliated 2D materials face the main technological issue of ferromagnetic electrode oxidation during the 2Ds integration process. As a twofold outcome, magnetoresistance (MR) signals are very difficult to obtain and, when they finally are, they are often far from expectations. We propose a fabrication method to circumvent this key issue for 2D-based spintronics devices. We report on the fabrication of NiFe/MoS2/Co spin valves with mechanically exfoliated multilayer MoS2 using an in situ fabrication protocol that allows high-quality nonoxidized interfaces to be maintained between the ferromagnetic electrodes and the 2D layer. Devices display a large …