An international team, including researchers from the University of Würzburg, has made a breakthrough in quantum physics by creating a special state of superconductivity. They built a hybrid device combining a superconductor with a topological insulator, a material that conducts electricity on its surface but not inside. This combination, known as a Josephson junction, allows precise control of superconducting properties using an external magnetic field. The discovery, led by Professor Charles Gould, could advance the development of quantum computers by helping stabilize quantum bits, which are currently very unstable due to sensitivity to external influences.
Quantum Physics Breakthrough: Superconductors and Magnetism Coexist
An international team of researchers, including scientists from the University of Würzburg, has made a significant breakthrough in quantum physics. They have successfully created a unique state of superconductivity, a development that could potentially accelerate the advancement of quantum computers.
Superconductors are materials that can conduct electricity without electrical resistance, making them ideal for electronic components in MRI machines, magnetic levitation trains, and particle accelerators. However, conventional superconductors are easily disrupted by magnetism. The researchers have now managed to construct a hybrid device that combines a stable superconductor, enhanced by magnetism, with a topological insulator, a special semiconductor material. This device’s function can be specifically controlled, overcoming the traditional vulnerability of superconductors to magnetic interference.
The Role of Topological Insulators
Topological insulators are materials that conduct electricity on their surface but not inside, due to their unique topological structure or the special arrangement of their electrons. According to Professor Charles Gould, a physicist at the Institute for Topological Insulators at the University of Würzburg, these insulators can be equipped with magnetic atoms, allowing them to be controlled by a magnet.
The researchers coupled the superconductors and topological insulators to form a Josephson junction, a connection between two superconductors separated by a thin layer of non-superconducting material. This combination allowed the researchers to merge the properties of superconductivity and semiconductors, creating a superconductor with the controllability of the topological insulator. By using an external magnetic field, the superconducting properties can now be precisely controlled.
The Proximity-Induced Fulde-Ferrell-Larkin-Ovchinnikov (p-FFLO) State
The combination of superconductors and topological insulators creates an exotic state known as the proximity-induced Fulde-Ferrell-Larkin-Ovchinnikov (p-FFLO) state. In this state, superconductivity and magnetism coexist, a rare occurrence as these are typically opposing phenomena. This new “superconductor with a control function” could be crucial for practical applications, such as the development of quantum computers.
Quantum computers operate on quantum bits (qubits), which can assume not just two but several states simultaneously, unlike conventional computers that operate on bits. However, qubits are currently very unstable due to their extreme sensitivity to external influences, such as electric or magnetic fields. The researchers’ discovery could potentially stabilize quantum bits, making them more viable for use in future quantum computers.
The International Quantum Research Team and Study
The experimental research was conducted by a team from the Chair of Experimental Physics III of Professor Laurens W. Molenkamp in Würzburg, in close collaboration with theoretical experts from the group of Professor F. Sebastian Bergeret of the Centre for Materials Physics (CFM) in San Sebastian, Spain, and Professor Teun M. Klapwijk of Delft University of Technology in the Netherlands.
The international research group received funding from various sources, including the Cluster of Excellence ct.qmat (Complexity and Topology in Quantum Materials), the German Research Foundation (DFG), the Free State of Bavaria, the Spanish Agencia Estatal de Investigación (AEI), the European research programme Horizon 2020, and the EU ERC Advanced Grant Programme.
The Cluster of Excellence ct.qmat
The Würzburg team is part of the Cluster of Excellence ct.qmat – Complexity and Topology in Quantum Matter, jointly run by the University of Würzburg (JMU) and Technische Universität (TU) Dresden since 2019. The cluster comprises over 300 scientists from more than thirty countries and four continents, studying topological quantum materials that reveal surprising phenomena under extreme conditions such as ultra-low temperatures, high pressure, or strong magnetic fields. ct.qmat is funded through the German Excellence Strategy of the Federal and State Governments and is the only Cluster of Excellence in Germany to be based in two different federal states.
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