A superconductor is a material that, when cooled below a certain temperature, can conduct electricity without any resistance.
In such a state, the current can flow indefinitely without energy dissipation. Two important fundamental properties in superconductivity are critical temperature and critical magnetic field.
What is Super Conductor?
A superconductor is a type of material that, when cooled to a critical temperature, can conduct electricity with no resistance or energy loss. It achieves a state of “perfect conductivity,” or superconductivity, where an electric current can flow indefinitely.
Superconductor definition
A superconductor is a type of material that conducts electricity with zero energy loss or resistance when cooled to a certain temperature. No energy is lost, resulting in a continuously flowing electrical current.
Superconductivity cancels out electrical resistance and magnetic fields in a quantum mechanical phenomenon “that is fundamentally different from the way conventional conductors work,” Ryan Milton, director at MC Electrical & Communications, told Built In.
The main challenge is in its application. According to Milton, finding superconductive materials that activate at higher, “more practical” temperatures, then figuring out how they work, is “a frontier that scientists and engineers are actively exploring.”
This breakthrough seemed to emerge in July 2023, when a team of South Korean researchers claimed to have discovered the first “room-temperature, ambient-pressure” superconductor, with material they dubbed LK-99.
Unfortunately, the claim is not supported by other scientists (the Condensed Matter Theory Center at the University of Maryland said that LK-99 is not a superconductor). Such a discovery would have been a game changer.
Additionally, superconductors have the ability to suspend other objects in midair. Called diamagnetic levitation, these materials block out external magnetic forces by creating their own magnetic field, which repels a force stronger than gravity, in an event known as the Meissner effect.
What is Critical Temperature in Super Conductor?
The critical temperature (TC) is an essential parameter dictating the transition of a material into its superconducting state. Below this critical temperature, certain materials exhibit extraordinary properties, conducting electricity without resistance and expelling magnetic fields.
This transition marks a fundamental shift in the material’s behavior as electrons pair up to form Cooper pairs, overcoming lattice vibrations to move coherently through the material.
Above TC, however, the material behaves as a regular conductor, with resistance and other conventional characteristics.
What is Critical Magnetic Field in Super Conductor?
The critical magnetic field (HC) is a defining threshold for the material’s behavior. Beyond this critical value, the superconducting state collapses, and the material reverts to its normal, resistive state.
This critical magnetic field represents the limit to which a superconductor can tolerate an applied magnetic field while maintaining its unique properties of zero resistance and perfect diamagnetism.
Above (HC), the magnetic field penetrates the superconductor, disrupting the coherence of the superconducting electron pairs and causing them to decouple, leading to the loss of superconductivity.
How Do Superconductors Work?
Regular conductors allow electricity to flow through them as a power source is applied. While this happens, something known as resistance occurs, which is when electrons climb from atom to atom, occasionally bumping into nuclei as they travel.
This process expends energy and heats up a material. Once that power source is removed, the electrical current will cease.
This is not the case for superconductors, as their unique atomic makeup would maintain this electrical current.
A normal conductor becomes a superconductor when electrons are paired to “cooperate with a material’s vibrating atoms,” explained Michael McHenry, a professor of materials science and engineering at Carnegie Mellon University.
These coupled electrons are known as Cooper pairs, and they spin in opposite directions as they move away from one another at the same speed.
So instead of electrons taking any erratic path, they navigate the oscillating waves shared between electrons and the structure of a material, moving in sync with vibrating nuclei without friction. That allows them to avoid collisions, or scattering — the culprits of resistance.
The colder a material gets, the more organized these pathways become. Traditionally, that number nears absolute zero the lowest possible limit on the thermodynamic scale, measuring at -459.67 degrees Fahrenheit, or 0 degrees Kelvin however, it depends on the material.
New breakthroughs in recent years have discovered so-called high-temperature superconductors. These materials, typically ceramic copper-oxides, exhibit properties of superconductivity at relatively warm temperatures previously thought impossible. They can be chilled by liquid nitrogen, which keeps cool at 77 Kelvin, or -321.1 Fahrenheit.
“In a superconducting state, the electrons within the Cooper pairs … behave collectively as a single entity rather than individual particles,” said Shubham Munde, a senior research analyst for Market Research Future and whose focus includes semiconductors.
“By pushing the boundaries of temperature limitations, scientists are continuously striving to find materials that exhibit superconductivity at even higher temperatures,” Munde said.
“The [aim is] to bring this transformative technology closer to room temperature, making it more feasible and cost-effective for widespread implementation in various industries.”
Types of Superconductors
There are two types of superconductors – type I and type II. Type I and Type II superconductors differ in their response to magnetic fields, characterized by their critical magnetic fields (HC) and critical temperatures (TC).
Type I Superconductors
Here are some characteristics of Type I superconductors.
- These superconductors have a single critical magnetic field (HC).
- Below their critical temperature (TC), they expel all magnetic fields from their interior, exhibiting perfect diamagnetism.
- Superconductivity stops once the applied magnetic field exceeds its critical magnetic field, and the material returns to a normal, resistive state.
- Type I superconductors are typically elemental metals like lead and mercury.
Type II Superconductors
Here are some characteristics of Type II superconductors.
- Type II superconductors have two critical magnetic fields (HC1 and HC2)
- Below their critical temperature (TC), they allow some penetration of magnetic fields into their interior.
- HC1 represents the lower critical magnetic field, where vortices start to penetrate the superconductor, but the bulk remains superconducting.
- HC2 is the upper critical magnetic field, beyond which the entire material becomes normal.
- The material exists in a mixed state between these two critical fields, allowing for the controlled penetration of magnetic fields.
- Type II superconductors can tolerate higher magnetic fields before losing superconductivity compared to Type I superconductors.
- They are often composed of compound materials, such as certain high-temperature superconductors and alloys like niobium-tin.
Differences Between Type I and Type II Superconductors
The key differences between Type I and Type II superconductors lie in their magnetic properties and critical field strengths. Below is a table summarizing the differences between the two.
| Feature | Type I Superconductors | Type II Superconductors |
| Critical Temperature (Tc) | Relatively low, usually below 10 K | Relatively high, can range from 10 K to over 100 K |
| Critical Magnetic Field (Hc) | Low, typically up to a few hundred Gauss | High, ranging from thousands to tens of thousands of Gauss |
| Magnetic Flux Expulsion | Complete expulsion of magnetic fields (Meissner effect) | Incomplete expulsion, some magnetic flux penetrates the material |
| Meissner Effect | Perfect | Imperfect |
| Superconducting State Stability | Low, susceptible to magnetic flux penetration and sudden transitions | High, more resistant to magnetic flux penetration and stable transitions |
| Multiple Transitions | Not observed | Can undergo multiple phase transitions with changing magnetic field |
| Applications | Low-power applications such as sensors and superconducting cables | High-field applications, including MRI machines and superconducting magnets |