Physics What kind of substance is a superconductor about superconductors?

A conductor that has no resistance under certain circumstances is called a superconductor. The phenomenon that superconductors have no resistance is called superconductivity.

Superconductors are conductors with zero resistance, which have not yet been discovered, and the so-called superconductors are the abbreviation of those conductors with very small resistance.

Objects such as germanium, silicon, selenium, gallium arsenide, and many metal oxides and metal sulfides, whose conductivity is between conductors and insulators, are called semiconductors.

Semiconductors have some special properties. For example, the relationship between the resistivity and temperature of semiconductors can be used to make thermistors (thermistors) for automatic control; Its photosensitive characteristics can be used to make photosensitive elements for automatic control, such as photocells, photocells and photoresistors.

Semiconductors also have one of the most important properties, and if trace impurities are properly incorporated into pure semiconductor substances, their conductivity will increase millions of times. This characteristic can be used to manufacture a variety of semiconductor devices for different purposes, such as semiconductor diodes, transistors, etc.

When one side of a semiconductor is made into a p-type region and the other side is made into an n-type region, a thin layer with special properties is formed near the junction, which is generally called a p-n junction. The upper part of the figure shows the diffusion of carriers at the interface between p-type semiconductors and n-type semiconductors (indicated by black arrows). The middle part shows the formation process of the p-n junction, indicating that the diffusion of the carriers is greater than the drift (indicated by a blue arrow, and a red arrow indicates the direction of the built-in electric field).

The lower part is the formation of the PN junction. Represents the dynamic equilibrium of diffusion and drift.

The significance of superconductor is as follows:The applications of superconductors can be divided into three categories: strong current applications, weak current applications, and diamagnetic applications.

High-current applications are high-current applications, including superconducting power generation, transmission, and energy storage; Weak current applications are electronic applications, including superconducting computers, superconducting antennas, superconducting microwave devices, etc.; Diamagnetic applications mainly include maglev trains and thermonuclear fusion reactors.

Superconducting magnets can be used to make AC superconducting generators, ferrofluid generators, and superconducting transmission lines. At present, superconducting quantum interferometers (squid) have been industrialized.

In addition, NBTI alloy and NB3SN, which are the main representatives of low-temperature superconducting materials, are mainly used in the commercial field in the medical field MRI (magnetic resonance imaging machine). As a field of scientific research, it has been applied to the LHC project, a large-scale project in Europe, to help mankind seek the origin of the universe and other scientific problems.

Superconductors have three basic properties: complete conductivity, complete diamagnetism, and flux quantization.

Fully conductive.

Perfect conductivity, also known as the zero resistance effect, refers to the phenomenon in which the temperature drops to a certain temperature and the resistance suddenly disappears.

Fully diamagnetic.

Complete diamagnetism, also known as the Meissner effect, "diamagnetism" refers to the phenomenon that when the magnetic field strength is lower than the critical value, the magnetic field lines cannot pass through the superconductor, and the magnetic field inside the superconductor is zero, and "completely" refers to the order of the two operations of lowering the temperature to reach the superconducting state and applying the magnetic field can be reversed. The reason for complete diamagnetism is that the surface of the superconductor is capable of generating a lossless diamagnetic superconducting current, which generates a magnetic field that cancels out the magnetic field inside the superconductor.

Flux quantization.

Flux quantization, also known as the Josephson effect, refers to the phenomenon that when the insulation layer between two superconductors is as thin as an atom, electron pairs can pass through the insulation layer to produce a tunnel current, that is, superconducting currents can be generated in the superconductor-insulator-superconductor structure.

In 1911, the famous Dutch physicist Carmelin Onnes liquefied nitrogen for the first time to obtain low temperatures. When Onnes placed the metallic mercury in cryogenic liquid nitrogen, he found that the resistance of the mercury dropped dramatically until it disappeared, and the resistance was zero! This was unbelievable at the time.

What is the principle of superconductivity? Physics is facing new challenges.

Superconductivity always occurs at very low temperatures, and the temperature at which superconductors undergo superconductivity is called the critical temperature. It is very troublesome to artificially make low temperatures, obviously, the higher the critical temperature, the more convenient the application of superconducting materials, the more valuable the application, so the scientific research armies of the world are committed to the development of superconducting materials with high critical temperatures, and superconducting materials have begun to enter the practical stage.

Analysis] Faced with the mystery of superconductivity with zero resistance, various theories emerged: some say that electron tunnels are generated; Some say that atoms are frozen at low temperatures, while others propose electron phenomenology (a theory based on assumptions) that assumes that two electrons form a Cooper pair ......at low temperaturesBut how are tunnels created, and how are atoms frozen? It's hard to explain.

The occurrence of superconductivity is a significant manifestation of the change in the rate of electrons outside the nucleus with temperature, and is an obvious feature of the change in the properties of matter caused by the movement of electrons outside the nucleus

At very low temperatures, the velocity of all the electrons of the object decreases, the valence electrons move in a fixed plane, and when the critical temperature is reached, the valence and electron velocity become lower and lower. The core is accustomed to the rapid operation of electrons outside the nucleus at room temperature, and the slow operation of valence and electrons causes the phenomenon of temporary loss of valence electrons in atoms. The core appropriates the valence electrons of the adjacent core, and the adjacent core appropriates it, and all the cores are appropriated to the neighbors in a certain direction, so that the outer electron commons are formed.

This state of common electrons in the outer shell of the nucleus is the superconducting state of matter, and the object in which the outer electrons of the nucleus are in the common state is a superconductor.

A substance whose resistivity is zero at a sufficiently low temperature and a sufficiently weak magnetic field.

Crystal hole bindings disappear.

Superconductors, also known as superconducting materials, refer to conductors with zero resistance at a certain temperature. In experiments, if the measured value of the conductor resistance is less than 10-25, the resistance can be considered to be zero.

There is no unified standard for the classification of superconductors, and the usual classification methods are as follows: They can be divided into the first type of superconductors and the second type of superconductors by the response of the material to the magnetic field: for the first type of superconductor, there is only a single critical magnetic field, and when the critical magnetic field is exceeded, the superconductivity disappears; For type 2 superconductors, they have two critical magnetic field values, between which the material allows part of the magnetic field to penetrate the material.

They can be divided into conventional superconductors (if they can be explained by the BCS theory or its corollaries) and non-traditional superconductors (if they cannot be explained by the above theories). The critical temperature at which superconductivity is achieved by the material can be divided into high-temperature superconductors and low-temperature superconductors

High-temperature superconductors are usually referred to as having a transition temperature of liquid nitrogen (greater than 77 K); Low-temperature superconductors usually refer to them that require other special techniques to reach their transition temperatures. By materials, they can be divided into chemical materials, superconductors, such as: lead and mercury; Alloy superconductors such as:

Niobium-titanium alloys; oxide superconductors, such as yttrium-barium-copper oxides; Organic superconductors, such as carbon nanotubes.

Explanation of superconductor [superconductor] at a certain temperature, the resistance of the object almost completely disappears, and the word is decomposed in the words of the late search Sakura.

Explanation of 超 超 ā crosses, exceeds: transcendence. Superb.

Go beyond. Excess. Overage.

Super. Overload. Overweight.

Overspend. Jump on and cross: "Hold Mount Tai to surpass the North Sea".

Outside a certain range: supernatural. Supersonic.

The phenomenon of superconductivity. Far away: super far away.

Extraordinary. A melancholy look: "Wuhou transcendence does not explain the explanation of conductors Substances or objects that can transmit electricity, heat, or sound code bundles explain in detail that substances with a large number of free charges and are prone to conduct electric current.

This substance also conducts heat easily. Generally, metals are conductors.