superconductivity

superconductivity
Name	Superconductivity
Discovered	1911
Discoverer	Heike Kamerlingh Onnes
Critical temperature	Varies (up to ~203 K under pressure)
Type	Zero electrical resistance; Meissner effect

superconductivity

Introduction

Superconductivity is a quantum condensed-matter phenomenon characterized by zero electrical resistance and the expulsion of magnetic flux (Meissner effect). First observed in metallic mercury by Heike Kamerlingh Onnes, it has since been studied across a spectrum of materials including elements, alloys, ceramics, and organic compounds. Research into superconductivity involves collaborations among institutions such as CERN, MIT, Stanford University, Max Planck Society and companies like IBM and Siemens. Major conferences and awards related to the field include the Nobel Prize in Physics, the APS March Meeting, the Materials Research Society symposia, and the Royal Society lectures.

History

The experimental discovery by Heike Kamerlingh Onnes in 1911 followed studies at the University of Leiden and work with liquefied gases pioneered by James Dewar. Early theoretical efforts included contributions from Walther Meissner and Robert Ochsenfeld who reported magnetic flux expulsion in 1933, and phenomenological models by Lev Landau and Vitaly Ginzburg in the 1950s. A major theoretical milestone was reached in 1957 with the BCS theory proposed by John Bardeen, Leon Cooper, and John Robert Schrieffer, honored by the Nobel Prize in Physics. Post-BCS developments involved the discovery of Type II superconductivity in alloys and the synthesis of high-temperature superconductors such as the cuprates discovered by Georg Bednorz and K. Alex Müller in 1986, which reshaped materials research agendas at institutions like Bell Labs and Los Alamos National Laboratory. Later breakthroughs include iron-based superconductors discovered by teams including researchers at Stanford University and NIMS, and hydride superconductors under extreme pressure reported by groups at Max Planck Institute for Chemistry and University of Tokyo.

Theoretical Foundations

The microscopic explanation of conventional superconductivity is given by BCS theory, where electrons form Cooper pairs mediated by lattice vibrations described in terms of phonons developed by Felix Bloch and Leo Kadanoff-influenced many-body techniques. Ginzburg–Landau theory, formulated by Lev Landau and Vitaly Ginzburg, provides a macroscopic order-parameter description used in studies at Princeton University and Harvard University. Quantum field theoretic and renormalization-group methods employed by researchers associated with Institute for Advanced Study and Perimeter Institute extend descriptions to unconventional pairing symmetries encountered in systems explored by Eliashberg-type formalisms and numerical approaches from groups at ETH Zurich and Oak Ridge National Laboratory. Concepts such as flux quantization and Josephson tunneling were developed by Brian Josephson and experimentally verified by teams at Cambridge University and Bell Labs, forming the basis for quantum-coherent devices pursued at Yale University and University of California, Berkeley.

Types and Materials

Superconductors are broadly classified as Type I and Type II; Type II materials include technologically important alloys and compounds studied at Argonne National Laboratory and Brookhaven National Laboratory. Conventional elemental superconductors like lead and mercury were central to early investigations at University of Leiden and University of Groningen. High-temperature cuprate superconductors discovered by Georg Bednorz and K. Alex Müller include families synthesized at IBM Zurich Research Laboratory and Tokyo Institute of Technology. Iron-based superconductors explored at Peking University and Tsinghua University revealed different pairing mechanisms. Organic superconductors and heavy-fermion compounds discovered in labs such as University of Geneva and University of Zürich display novel symmetry, while hydride superconductors under high pressure investigated by University of Innsbruck and Lawrence Berkeley National Laboratory approach room-temperature regimes when compressed in diamond anvil cells used in facilities like Max Planck Institute for Chemistry.

Experimental Techniques and Measurement

Key experimental techniques include four-probe resistivity measurements practiced in facilities at Georgia Institute of Technology and University of Cambridge, magnetic measurements via SQUID magnetometers developed with contributions from IBM and Bell Labs, and muon spin rotation experiments at institutes like TRIUMF and Paul Scherrer Institute. Spectroscopic tools such as angle-resolved photoemission spectroscopy (ARPES) at ALS and SLAC National Accelerator Laboratory, scanning tunneling microscopy (STM) at Max Planck Institute for Solid State Research, and neutron scattering at Oak Ridge National Laboratory elucidate pairing symmetry and gap structure. High-pressure methods employing diamond anvil cells are used by groups at University of Tokyo and University of Edinburgh to probe hydride phases; cryogenic technologies from Cryomech and Oxford Instruments enable dilution refrigerator experiments relevant to quantum computing research at Microsoft and Google.

Applications and Technologies

Applications leverage zero-resistance and magnetic properties in devices such as MRI magnets manufactured by companies like GE Healthcare and Siemens Healthineers, particle accelerator magnets at CERN and Fermilab, and superconducting quantum interference devices (SQUIDs) used in geophysics by teams at USGS and in biomagnetism at Harvard Medical School. Superconducting qubits developed at IBM, Google, and Rigetti Computing underpin quantum processors. Power applications explored by Siemens and Hitachi include superconducting cables, fault current limiters, and magnetic energy storage demonstrated in pilot projects at EPRI and National Grid.

Challenges and Future Directions

Major challenges include raising critical temperatures and critical currents in practical materials—a focus of research at DARPA and the European Commission—and understanding unconventional mechanisms pursued by theorists at Perimeter Institute and Institute for Advanced Study. Materials discovery via high-throughput computations at Argonne National Laboratory and machine learning approaches at Google Research aim to accelerate progress. Integration of superconductors into scalable quantum technologies is pursued by consortia including Quantum Economic Development Consortium and national labs like Sandia National Laboratories. Long-term directions encompass room-temperature superconductivity, ambient-pressure hydride stabilization studied at Max Planck Institute for Chemistry, and novel topological superconductors investigated at Stanford University and Princeton University that could enable fault-tolerant quantum computing.

Category:Condensed matter physics