34.6 High-temperature Superconductors
4 min read•june 18, 2024
Superconductors are materials that conduct electricity with zero resistance below a . This amazing property allows for groundbreaking applications in technology, from MRI machines to particle accelerators and .
The critical temperature of a superconductor is crucial for practical use. Lower temperatures require expensive cooling systems, while higher temperatures allow for more accessible and cost-effective methods, expanding the potential for real-world applications.
Superconductivity and Its Applications
Mechanism of superconductors
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- Superconductors conduct electricity with zero resistance below a critical temperature
- Electrons form , which move through the material without scattering or energy loss, allowing for the flow of electrical current without any dissipation of energy
- Practical applications of superconductors in technology include:
- machines
- generate strong, stable magnetic fields for high-resolution imaging of the human body
- Particle accelerators ()
- Superconducting magnets guide and focus particle beams for high-energy physics experiments to study fundamental particles and forces
- Power transmission lines
- Superconducting cables efficiently transport electricity over long distances with minimal losses, reducing the need for multiple power stations
- (Maglev) trains (Shanghai Maglev)
- Superconducting magnets create strong magnetic fields for levitation and propulsion, reducing friction and increasing efficiency for high-speed transportation
- ()
- Highly sensitive magnetometers measure extremely weak magnetic fields in various applications, such as brain imaging () and geophysical surveys for mineral exploration
- machines
Impact of critical temperature
- Critical temperature () is the temperature below which a material becomes superconducting
- Above , the material behaves as a normal conductor with electrical resistance
- Below , the material exhibits and expels magnetic fields (), allowing for lossless current flow and magnetic levitation
- The critical temperature is crucial for the practical use of superconductors
- Lower requires more complex and expensive cooling systems, such as liquid helium (), limiting the widespread application of superconductors due to high operational costs and technical challenges ()
- Higher allows for more accessible and cost-effective cooling methods, such as liquid nitrogen (), expanding the potential for practical applications and reducing the overall cost of implementing superconducting technologies
Conventional and High-Temperature Superconductors
Conventional vs high-temperature superconductors
- Conventional superconductors
- Typically pure metals or simple alloys (, , )
- Low critical temperatures () below , requiring expensive and complex cooling systems, such as liquid helium
- Well-understood theory () explains the mechanism of involving and Cooper pair formation
- Limited practical applications due to the low and high cooling costs
- High-temperature superconductors (HTS)
- Complex ceramic materials, often containing copper oxide layers ( such as , )
- Higher critical temperatures () above (liquid nitrogen temperature), allowing for more accessible and cost-effective cooling methods and expanding the potential for practical applications
- Mechanism of superconductivity not fully understood; BCS theory does not adequately explain HTS behavior, suggesting the involvement of other factors such as magnetic interactions or electron correlations
- Challenges in fabrication and application due to the brittle nature of ceramic materials and the difficulty in creating long, flexible wires for large-scale applications (power transmission, superconducting magnets)
- Key differences and challenges
- HTS materials have higher values, allowing for more practical and cost-effective applications compared to conventional superconductors
- HTS materials are more complex and difficult to fabricate compared to conventional superconductors due to their ceramic nature and layered structure
- The lack of a comprehensive theory for HTS hinders the understanding and optimization of these materials, requiring further research to elucidate the underlying mechanisms
- The brittle nature of HTS ceramics poses challenges in creating flexible wires and cables for large-scale applications, necessitating the development of innovative fabrication techniques (thin film deposition, wire-in-tube method)
Advanced concepts in high-temperature superconductivity
- : A phenomenon in which magnetic flux lines are trapped or "pinned" within the superconductor, enhancing its current-carrying capacity and magnetic field strength
- : An energy range in the electronic structure of some high-temperature superconductors where the density of states is reduced, potentially related to the pairing mechanism
- : A type of electron pairing symmetry observed in many high-temperature superconductors, different from the s-wave pairing found in conventional superconductors
- : A newer class of high-temperature superconductors discovered in 2008, offering an alternative to cuprates and providing new insights into the mechanisms of high-temperature superconductivity
Key Terms to Review (38)
Angle-Resolved Photoemission Spectroscopy: Angle-Resolved Photoemission Spectroscopy (ARPES) is a powerful experimental technique that allows the direct measurement of the electronic structure of materials by analyzing the energy and angular distribution of photoelectrons emitted from a sample when exposed to high-energy photons. This technique provides valuable insights into the electronic properties of materials, particularly in the context of high-temperature superconductors.
BCS Theory: BCS theory, also known as the Bardeen-Cooper-Schrieffer theory, is a microscopic theory that explains the phenomenon of superconductivity. It describes how electrons in a superconductor can form pairs, known as Cooper pairs, which then condense into a quantum state, allowing for the flow of electricity without resistance.
Bednorz and Müller: Bednorz and Müller were two physicists who made a groundbreaking discovery in the field of high-temperature superconductivity. In 1986, they successfully synthesized and characterized a new class of ceramic materials that exhibited superconducting properties at much higher temperatures than previously known, paving the way for advancements in various applications of superconductivity.
BSCCO: BSCCO is a family of high-temperature superconducting materials composed of bismuth, strontium, calcium, copper, and oxygen. These materials exhibit superconductivity at relatively high temperatures compared to traditional superconductors, making them a significant advancement in the field of superconductivity.
Coherence Length: Coherence length is a measure of the distance over which a wave maintains a fixed phase relationship with itself. It is an important concept in the study of wave interference and has significant implications in the fields of thin film interference and high-temperature superconductors.
Cooper Pairs: Cooper pairs are pairs of electrons that are bound together in a superconductor, allowing for the flow of electricity without resistance. This phenomenon is crucial to understanding the behavior of high-temperature superconductors, materials that can conduct electricity with zero resistance at relatively high temperatures compared to traditional superconductors.
Critical Temperature: The critical temperature is the temperature at which a material transitions from a normal state to a superconducting state, exhibiting zero electrical resistance and the ability to expel magnetic fields. This phenomenon is particularly relevant in the context of high-temperature superconductors, materials that can achieve superconductivity at much higher temperatures compared to traditional superconductors.
Cryogenic Cooling: Cryogenic cooling refers to the process of achieving extremely low temperatures, typically below -150°C (-238°F), often using liquid gases like helium or nitrogen. This method is crucial for cooling materials and systems to observe their properties at these low temperatures, especially in the study of high-temperature superconductors where it can enhance their superconducting properties by minimizing resistance and allowing for more efficient energy transfer.
Cuprates: Cuprates are a class of ceramic materials that exhibit high-temperature superconductivity, a phenomenon where certain materials can conduct electricity without resistance at relatively high temperatures compared to traditional superconductors. These materials are of great interest in the field of condensed matter physics and have potential applications in various technologies.
D-wave Pairing: d-wave pairing is a type of superconducting pairing mechanism that occurs in high-temperature superconductors. It is characterized by a more complex order parameter with a d-wave symmetry, as opposed to the s-wave pairing found in conventional superconductors.
Electron-Phonon Interactions: Electron-phonon interactions refer to the coupling between the motion of electrons and the vibrations of the crystal lattice (phonons) in a material. This interaction plays a crucial role in understanding the behavior of materials, particularly in the context of high-temperature superconductors.
Flux Pinning: Flux pinning is a phenomenon that occurs in type-II superconductors, where the magnetic flux lines within the material become trapped or 'pinned' in place, preventing the flow of electrical current. This pinning effect is crucial for the practical applications of high-temperature superconductors, as it helps to maintain the superconducting state and improve the material's ability to carry high currents without energy loss.
Iron-based Superconductors: Iron-based superconductors are a class of high-temperature superconducting materials that contain iron as a key component. These materials exhibit the ability to conduct electricity without resistance at relatively high temperatures compared to traditional superconductors, making them a promising alternative for various applications.
Kamerlingh Onnes: Kamerlingh Onnes was a Dutch physicist who, in 1911, discovered the phenomenon of superconductivity - the ability of certain materials to conduct electricity without resistance at extremely low temperatures. His groundbreaking work in cryogenics and the study of materials at very low temperatures laid the foundation for the development of high-temperature superconductors, which have revolutionized various fields of science and technology.
Large Hadron Collider: The Large Hadron Collider (LHC) is the world's largest and most powerful particle accelerator, used to study the most fundamental components of matter and the forces that govern them. It plays a crucial role in the fields of particle physics, nuclear physics, and cosmology, connecting various topics in physics, including the force on a moving charge in a magnetic field, relativistic energy, the creation of matter from energy, and the application of high-temperature superconductors.
Lead: Lead is a dense, soft, and malleable metal that has been used in various applications throughout history. In the context of high-temperature superconductors, lead plays a crucial role in the development and understanding of these materials.
London Equations: The London equations are a set of fundamental equations that describe the behavior of superconductors, particularly their response to external magnetic fields. They were developed by the brothers Fritz and Heinz London in 1935 and are essential for understanding the properties of high-temperature superconductors.
Maglev Trains: Maglev trains, or magnetic levitation trains, are a type of high-speed rail transportation system that uses powerful electromagnets to levitate the train cars above the tracks, allowing for frictionless and near-silent movement. This innovative technology is closely linked to the development of high-temperature superconductors, which enable the efficient generation of the strong magnetic fields required for levitation.
Magnetic Levitation: Magnetic levitation, or maglev, is a technology that uses magnetic fields to lift and propel an object without physical contact. This phenomenon is achieved by the repulsive and attractive forces between superconducting or permanent magnets, allowing objects to float or move frictionlessly above a surface.
Magnetic Resonance Imaging: Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that uses strong magnetic fields and radio waves to create detailed images of the body's internal structures. It is a powerful diagnostic tool that has revolutionized the field of medicine by providing healthcare professionals with a comprehensive view of the human body without the use of ionizing radiation.
Magnetic resonance imaging (MRI): Magnetic resonance imaging (MRI) is a medical imaging technique that uses powerful magnets and radio waves to create detailed images of the inside of the body. It relies on the principles of nuclear magnetic resonance, where atomic nuclei align with a magnetic field and emit signals when perturbed by radio waves.
Magnetoencephalography: Magnetoencephalography (MEG) is a non-invasive neuroimaging technique that measures the magnetic fields generated by the electrical activity of the brain. It is a powerful tool for studying the brain's functions and is particularly useful in the context of high-temperature superconductors, as it can provide insights into the complex electronic properties of these materials.
MEG is based on the principle that the electrical currents flowing through the brain generate small magnetic fields, which can be detected by highly sensitive magnetic sensors called superconducting quantum interference devices (SQUIDs). These sensors are cooled to extremely low temperatures, typically using liquid helium, in order to achieve the necessary sensitivity to measure the weak magnetic fields produced by the brain.
Meissner Effect: The Meissner effect is a phenomenon observed in superconductors, where a superconductor expels any magnetic field from its interior when it is cooled below its critical temperature. This effect is a key characteristic of superconductors and is closely related to their ability to perfectly conduct electricity without resistance.
Mercury: Mercury is a chemical element with the symbol Hg and atomic number 80, known for being the only metal that is liquid at room temperature. In various contexts, it plays a significant role in understanding satellite motion through gravitational interactions and in high-temperature superconductors as a superconductor material, influencing both fields significantly.
Neutron Scattering: Neutron scattering is a powerful technique used to study the structure and dynamics of materials at the atomic and molecular level. It involves the interaction of neutrons with the nuclei of atoms, providing valuable insights into the properties and behavior of various materials, including high-temperature superconductors.
Niobium-Titanium: Niobium-titanium (NbTi) is a type of superconducting alloy composed of niobium and titanium. It is one of the most widely used superconducting materials, particularly in the context of high-temperature superconductors, due to its excellent superconducting properties and ability to maintain superconductivity at relatively high magnetic fields.
Order Parameter: The order parameter is a measure of the degree of order or organization in a system, particularly in the context of phase transitions. It is a crucial concept in the understanding of high-temperature superconductors, as it helps describe the transition from a normal metal to a superconducting state.
Perfect Diamagnetism: Perfect diamagnetism is a phenomenon observed in certain materials, particularly superconductors, where an applied magnetic field is completely expelled from the interior of the material. This results in the material exhibiting a perfect diamagnetic response, with a magnetic susceptibility of exactly -1.
This property is a hallmark of superconductors, as it allows them to levitate above a magnetic field, a behavior known as the Meissner effect. Perfect diamagnetism is a crucial characteristic that distinguishes superconductors from other types of magnetic materials.
Pseudogap: The pseudogap is a phenomenon observed in the electronic density of states of certain materials, particularly high-temperature superconductors, where there is a partial depletion of electronic states near the Fermi level, even in the absence of superconductivity. This partial gap in the electronic spectrum is referred to as the pseudogap.
SQUIDs: SQUIDs, or Superconducting Quantum Interference Devices, are highly sensitive magnetometers that can detect extremely small magnetic fields. They are based on the principles of superconductivity and quantum interference, making them invaluable tools in various scientific and technological applications.
Superconducting Magnets: Superconducting magnets are a type of electromagnet that utilizes superconducting materials to generate extremely strong and stable magnetic fields. These magnets are essential in various applications, including high-energy physics experiments, medical imaging, and transportation systems.
Superconducting Quantum Interference Devices: Superconducting Quantum Interference Devices (SQUIDs) are highly sensitive magnetometers capable of detecting extremely small magnetic fields. They are based on the principles of quantum mechanics and superconductivity, making them valuable tools in various scientific and technological applications.
Superconductivity: Superconductivity is a remarkable phenomenon where certain materials, when cooled below a critical temperature, lose all electrical resistance and can conduct electricity without any energy dissipation. This unique property has significant implications in the fields of physics and high-temperature superconductors.
Type-I Superconductors: Type-I superconductors are a class of superconducting materials that exhibit a complete loss of electrical resistance below a critical temperature. They are characterized by their ability to expel magnetic fields, a phenomenon known as the Meissner effect, which distinguishes them from normal conductors.
Type-II Superconductors: Type-II superconductors are a class of superconducting materials that exhibit a unique behavior in the presence of strong magnetic fields. Unlike type-I superconductors, which completely expel magnetic fields, type-II superconductors allow the partial penetration of magnetic fields, leading to the formation of quantized magnetic flux lines within the material.
YBCO: YBCO, or Yttrium Barium Copper Oxide, is a type of high-temperature superconductor material that has revolutionized the field of superconductivity. This ceramic compound, with the chemical formula YBa2Cu3O7-δ, exhibits superconducting properties at temperatures significantly higher than traditional superconductors, making it a crucial advancement in the development of practical superconducting applications.
Yttrium Barium Copper Oxide: Yttrium barium copper oxide, commonly referred to as YBCO, is a type of ceramic material that exhibits high-temperature superconductivity. It is a complex copper oxide compound consisting of yttrium, barium, and copper, and is considered a key material in the development of practical superconducting technologies.
Zero Electrical Resistance: Zero electrical resistance, also known as superconductivity, is a state of matter in which a material exhibits the complete absence of electrical resistance, allowing electric current to flow without any loss of energy. This phenomenon is of great significance in the context of high-temperature superconductors, as it enables the development of highly efficient and energy-saving technologies.