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Educated search for high-temperature superconductivity in novel electronic materials

English title Educated search for high-temperature superconductivity in novel electronic materials
Applicant Rønnow Henrik M.
Number 180652
Funding scheme Croatian-Swiss Research Programme (CSRP)
Research institution EPFL SB IPHYS CQSL Computational Quantum Science Laboratory)
Institution of higher education EPF Lausanne - EPFL
Main discipline Condensed Matter Physics
Start/End 01.01.2019 - 31.12.2022
Approved amount 344'357.00
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All Disciplines (2)

Discipline
Condensed Matter Physics
Material Sciences

Keywords (4)

Metal-insulator transition; Vanadates; Unconventional superconductivity; Sulfosalts

Lay Summary (German)

Lead
Supraleitung ist ein einzigartiger quantenmechanischer Materiezustand, der elektrische Energie völlig verlustfrei zu transportieren vermag. Die Entdeckung von Materialien mit supraleitenden Eigenschaften bei Raumtemperatur würde die Art und Weise revolutionieren wie wir grosse gesellschaftliche Herausforderungen angehen können - von Energie, Information bis hin zu Gesundheit.
Lay summary

Bislang gibt es zwei Klassen von supraleitenden Materialien. Konventionelle Supraleiter, die wir zwar theoretisch gut verstehen, die aber bis auf wenige Ausnahmen (etwa sehr teure Magnetresonanztomographie-Maschinen in Krankenhäusern) für praktische Anwendungen ungeeignet sind, da sie nur bei Temperaturen unter minus 250 Grad Celsius oder bei extrem hohen Drücken funktionieren. Unkonventionelle Supraleiter wurden mit Sprungtemperaturen bis zu minus 100 Grad Celsius entdeckt und möglicherweise könnten Vertreter dieser Klasse sogar bei Raumtemperatur funktionieren. Allerdings war die Entdeckung solcher unkonventionellen Supraleiter mangels einer adäquaten Theorie eher vom Zufall geleitet. In diesem Projekt zielen wir auf die elementaren Merkmale von Hochtemperaturesupraleitern ab und untersuchen auf der Suche nach neuen Hochtemperatursupraleitern Materialien mit ähnlichen Merkmalen.

Dieses Vorhaben ist ein gemeinsames Projekt des Instituts für Physik an der Universität Zagreb und des Labors für Quantenmagnetismus an der Ecole Polytechnique de Lausanne. Die Bündelung unserer Anstrengungen erlaubt es uns alle notwendigen Schritte auf dem Weg zur Erforschung neuer Klassen von elektronischen Materialien mit dem Potential für unkonventionelle Supraleitung zu gehen, von theoretischen Vorhersagen, über Materialsynthese und Charakterisation, bis hin zu modernsten Transport- und Spektroskopiemessungen unter extremen Temperatur-, Magnetfeld- und Druckbedingungen. Diese Kollaboration erlaubt den Brückenschlag zwischen zwei Instituten mit komplementären Kompetenzen und Ressourcen, über den wir den Austausch von Studenten, Doktoranden und wissenschaftlichen Mitarbeitern planen.


Direct link to Lay Summary Last update: 30.10.2018

Lay Summary (English)

Lead
Superconductivity is a unique state of matter where quantum mechanics lead to the astonishing ability to transport electric energy completely loss-less. If we could discover materials with this property at ambient temperature, it would revolutionize how we tackle society's grand challenges from energy and information to health.
Lay summary
To date there exist two classes of superconducting materials. Conventional superconductors for which we have a theoretical understanding, but which require cooling below minus 250 degrees or extremely high pressures to function, making them impractical for all but a few applications (such as very expensive magnetic resonance imaging machines in hospitals). Unconventional superconductors have been discovered to function up to minus 100 degrees, and could potentially be discovered to function even at ambient temperature. However, in the absence of a good theory for unconventional superconductors, their discovery has so far been accidental. In this project we target key signatures of known high temperature superconductors and explore materials with similar signatures in the search for new high temperature superconductors.

This endeavor is a joint project between Institute of Physics at University of Zagreb and Laboratory for Quantum Magnetism at Ecole Polytechnique de Lausanne. By joining forces, the collaboration will include all necessary steps for
exploring new classes of electronic materials with potential for unconventional superconductivity, from theoretical predictions over materials synthesis and characterization to state of the art transport and spectroscopic studies under extreme conditions of temperature, magnetic field and pressure. The collaboration will form a bridge between two institutes with complementary expertise and capabilities through which we envisage undergraduate and graduate student as well as scientific staff exchange.
Direct link to Lay Summary Last update: 30.10.2018

Responsible applicant and co-applicants

Gesuchsteller/innen Ausland

Employees

Name Institute

Publications

Publication
Synthesis of murunskite single crystals: A bridge between cuprates and pnictides
Tolj Davor, Ivšić Trpimir, Živković Ivica, Semeniuk Konstantin, Martino Edoardo, Akrap Ana, Reddy Priyanka, Klebel-Knobloch Benjamin, Lončarić Ivor, Forró László, Barišić Neven, Ronnow Henrik M., Sunko Denis K. (2021), Synthesis of murunskite single crystals: A bridge between cuprates and pnictides, in Applied Materials Today, 24, 101096-101096.

Collaboration

Group / person Country
Types of collaboration
Department of Physics, University of Zagreb Croatia (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel

Associated projects

Number Title Start Funding scheme
198101 ExtremeP: A Joint Pressure Capability for Complementary Neutron and Muon Experiments on Quantum Materials 01.04.2021 R'EQUIP
189644 Versatile high sensitivity and throughput magnetometer for quantum, functional and applied materials 01.03.2020 R'EQUIP

Abstract

We propose a joint research project combining the scientific expertise and technical capabilities of teams respectively at University of Zagreb in Croatia and EPFL in Switzerland. By joining forces, the collaboration will include all necessary steps for exploring new classes of electronic materials with potential for unconventional superconductivity, from theoretical predictions over materials synthesis and characterization to state of the art transport and spectroscopic studies under extreme conditions of temperature, magnetic field and pressure. The collaboration will form a bridge between two institutes with complementary expertise and capabilities through which we envisage undergraduate and graduate student as well as scientific staff exchange.Modern functional materials defy the textbook distinction between metals and ionic insulators: many are ionic metals. The crystal structure clearly shows that the metallic state at the Fermi surface must contain a component of the non-metallic anion orbitals, because they bridge the metal positions in the crystal lattice. At the same time, the proximity of this metallic state to a metal-insulator transition (MIT) means that ionic metals are only superficially like intermetallic alloys or A15 phases, whose crystallization energy is due to metallic bonding. Because the MIT in ionic metals is usually achieved by modest variations in temperature, pressure, or impurities, hardly even affecting the crystal structure, it is obvious that the ionic background is responsible for bulk cohesion even in the metallic state, in sharp contrast to metals and alloys, where conductivity disappears in general only at the price of evaporating the sample.Over the past three decades, the most extensively studied ionic metals were the high-temperature superconductors: oxides and pnictides, where the coordinating anions are oxygen and arsenic/phosphorus, respectively. More recently, several other oxide families have shown surprising metallic behavior, e.g. delafossites, rare-earth nickelates, and vanadium oxides, or vanadates. Of these, cuprates and pnictides are the subject of applicants’ long-standing expertise and source of significant synergisms expected in this project.The project is based on several insights into high-temperature cuprate and pnictide superconductors, which it aims to bring together in the investigation of a new generation of modern functional materials: sulfosalts and metallic vanadates. The key insights are:1.The conducting electrons in the superconducting cuprates and pnictides show Fermi liquid (FL) behavior experimentally. However, in cuprates at low doping and temperature all FL properties are scaled with the doping x, not the total charge 1+x.2.Superconductivity (SC) is present in cuprates until the FL properties begin to scale with 1+x, when SC disappears. This in turn means that the Mott-like localized one unit of charge per unit cell is an essential ingredient of the SC mechanism itself.3.The doping mechanism in the cuprates is ionic. Doping both introduces x charge carriers in the Cu-O plane and affects the chemical balance between the open orbitals, inducing them to metallize.Bringing these insights together, to fine-tune functional properties (e.g., high-temperature superconductivity), one must affect the balance between covalency and ionicity in the same material, indeed in the same unit cell or atom, as is observed with copper oxide in the cuprates. The localized one is part of the 3D ionic background (the parent compound) in which the presumably/prevailingly 2D metallization occurs. The chemical potential is simultaneously a physical parameter of the latter FL and a chemical parameter of the reaction between active orbitals, which provides the functional electrons.This dual role of the chemical potential is a new way of looking at functional materials. We propose to explore it in two similar yet complementary classes of materials, the sulfosalts and the vanadium oxides. Among the sulfosalts, we choose murunskite, which we intend to develop into a whole class of materials by itself, doping along two qualitatively different electronic axes. Among the vanadates, well known Mott-insulator systems, we concentrate on the poorly investigated V7O13 and doped V2O5, because one is the only one metallic at ambient pressure and all temperatures, while the other is superconducting under pressure. Thus, both most clearly fall on the interesting functionalized side of the ionic metal properties.Sulphides are less ionic than oxides. Thus, they display surprising crystallochemical flexibility and superior tunability of the valence of the transition metal ions, including possibilities of metallization. This results in a large variety of interesting electronic, magnetic and mechanical properties. The large compressibility of sulphur compounds helps to induce the phase transitions by pressure, which renders particularly interesting the studies of structural and electronic properties of those systems under pressure, which are one of the domains of applicants’ expertise.We propose to synthesize murunskite K2(Fe,Cu)4S4 (currently not available in a monocrystalline form) and to study it along up to two doping axes, (Fe,Cu) and replacing K with Ca or Ba. In the natural composition K2FeCu3S4, murunskite is a superparamagnetic insulator. Our primary objective is to find metallic phases in its phase diagram and study their transport properties, especially with respect to superconductivity (and thermolectricity). Temperature and pressure (hydrostatic and uniaxial) will be the main thermodynamic parameters in multiple doping compositions.V7O13 belongs to the family of so-called Magnéli phases, represented by the generic formula VnO2n-1. The end members of the series, V2O3 (n = 2) and VO2 (n = 8) have vanadium in 3+ and 4+ oxidation state, respectively. Vanadium in 4+ state is a d1 ion, analogous to the d9 copper ion found in all cuprate high-temperature superconductors. While doping the cuprates is performed by introducing holes/electrons in the CuO2 planes (thus shifting slowly away from Cu d9 configurations by metallization of the polar Cu-O bond), Magnéli phases offer a natural ‘self-doping’ of electrons, introducing d2 configurations of vanadium ions to accommodate the varying stoichiometry. In this respect the lack of the MIT in V7O13 represents an exciting opportunity for the investigation of the relation between electron-electron interactions and superconductivity. We suspect that a key element of the absence of superconductivity in these materials is a complete, first-order like, dissociation of the Mott phase and thus non-existence of the charge excitation related to the localized carrier that is presumably present in cuprates. In the language of bond polarity (metallicity vs. covalency), there is no window of simultaneous localization of one charge on the metal cation and covalent sharing of the other with the coordinating oxygen, as in the cuprates. However, it is remarkable that doped vanadium oxide A0.33V2O5, (A=Na,Li,Ag) is superconducting when the charge-order insulating state is suppressed with pressure of ~8 GPa. Given the layered structure of the VnO2n-1 series, the A-component doping levels can be controlled quasi-continuously. Thus doping bridges the gaps between the n-1, n and n+1 members of the Mott-insulating series.Both directions of research require an extensive experimental and theoretical effort to fully address its enormous potential. To do this, it is imperative to combine two teams complementary to each other, ensuring a wide coverage of techniques and expertise. Additionally, the nature of this project, namely the discovery of new materials, ensures that the established synergetic processes will continue to be present even after the project officially ends.
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