Materials (III)

This chapter focuses on organic and nanoscale superconducting systems. The tetramethyl-tetraselenafulvalene (TMTSF) and ethylenedithiotetrathiafulvalene (ET) organic families, along with the fullerides, are described. Special attention is paid to graphene-like structures, which are examples of two-dimensional systems. As for nanoscale systems, small-scale nanoscale structures are introduced and the pairing in aromatic molecules, like coronene, is discussed. The presence of the energy shell in some nanoclusters makes the pairing of electrons with opposite projections of orbital momenta perfectly realistic. This phenomenon has been observed experimentally for some aluminium clusters with a Tc on the order of 120 K. The nano-based tunnelling networks can transfer a macroscopic dissipationless current. Interface superconductivity is discussed, with a special focus on the FeSe/SrTiO3 system. The dream of room temperature superconductivity, envisioned shortly after the discovery of the phenomenon, has become perfectly realistic. This final chapter on materials describes various paths towards to this goal.

The interface superconductivity of Bi2Se3/Fe–Se heterostructure

Bi2Se3/Fe–Se heterostructures on Si(100) substrates have been prepared by radio frequency magnetron sputtering technique. The thickness of FeSe2 film is an important factor for the properties of Bi2Se3/Fe–Se heterostructures. Our Bi2Se3/Fe–Se heterostructural samples showed ferromagnetism, which increase with increasing thickness of FeSe2 layer. However, when the FeSe2 layer is as thin as 20 nm, superconductivity could be observed through magnetization measurements, due to the existence of superconducting Fe–Se. Thus the Bi2Se3/Fe–Se heterostructure provides an approach to achieve both ferromagnetism and superconductivity simultaneously in interface, as well as to realize the interplay between a superconductor and a topological insulator.

SCANNING TUNNELING MICROSCOPIC STUDY OF THE INTERFACE SUPERCONDUCTIVITY

It has been 30 years since the Nobel Prize was awarded for scanning tunneling microscope (STM) in the year 1986, and there have been many instrumental developments and experimental achievements based on STM. In consideration of the strong capability and the extreme versatility in imaging, manipulating, and spectroscopy at the atomic level, STM has witnessed remarkable breakthroughs in many disciplines of condensed matter physics. In this paper, we will focus on recent STM studies on the interface superconductivity, which demonstrate a novel platform for exploring two dimensional superconductors and even high temperature superconductors by means of interface engineering.

Study of high-Tc interface superconductivity in La1.55Sr0.45CuO4/La2CuO4 heterostructures at high magnetic fields and frequencies

We have synthesized heterostructures that consist of a layer of a cuprate insulator, La2CuO4, and a layer of a nonsuperconducting cuprate metal, La[Formula: see text]Sr[Formula: see text]CuO4. Such bilayers show high-[Formula: see text] interface superconductivity confined within a single CuO2 plane. Here, we explore the behavior of interface superconductivity at high frequencies (up to 50 MHz) under high magnetic fields (up to 56 T). We find that interface superconductivity persists up to very high perpendicular fields (exceeding 40 T). The critical magnetic field [Formula: see text] shows an upward divergence with decreasing temperature suggestive of vortex-lattice melting, similar to what is observed in bulk superconducting cuprates.

Surface and Interface Superconductivity

This article focuses on surface and interface superconductivity, a pivotal area of mesoscopic superconductivity. It discusses theoretical ideas regarding superconductivity in the 2D limit; pairing symmetry in systems with broken inversion symmetry and in the presence of Rashba spin–orbit interaction; and coupling of substrate phonon modes to layer electronic states to induce or enhance the superconducting condensate. It also reviews the experimental ongoing efforts to fabricate, characterize, and measure these systems, with particular emphasis on oxide materials. Superconductivity in two dimensions, in ultra-thin metals on Si(111), and at the LaAlO3/SrTiO3 interface is examined. The article concludes with an analysis of theoretical propositions aimed at realizing and testing novel superconducting states occurring at the surfaces and interfaces.