Type-I superconductor

The interior of a bulk <a href="/facts/Superconductor/pqQAlSzJ">superconductor</a> cannot be penetrated by a weak <a href="/facts/Magnetic_field/Ta8Ev588">magnetic field</a>, a phenomenon known as the <a href="/facts/Meissner_effect/VJLdDzzE">Meissner effect</a>. When the applied magnetic field becomes too large, superconductivity breaks down. Superconductors can be divided into two types according to how this breakdown occurs. In type-I superconductors, superconductivity is abruptly destroyed via a <a href="/facts/First_order_phase_transition/eLP2BY8R">first order phase transition</a> when the strength of the applied field rises above a critical value Hc. This type of superconductivity is normally exhibited by pure metals, e.g. aluminium, lead, and mercury. The only alloys known up to now which exhibit type I superconductivity are tantalum silicide (TaSi2). and BeAu 
The <a href="/facts/Covalent_superconductor/0ujLMbAd">covalent superconductor</a> SiC:B, <a href="/facts/Silicon_carbide/kQLVAYbr">silicon carbide</a> heavily doped with boron, is also type-I.
Depending on the demagnetization factor, one may obtain an intermediate state. This state, first described by <a href="/facts/Lev_Landau/lNXQTC49">Lev Landau</a>, is a phase separation into macroscopic non-superconducting and superconducting domains forming a <a href="/facts/Husimi_Q_representation/Tul5cvP9">Husimi Q representation</a>.
This behavior is different from <a href="/facts/Type-II_superconductors/8V4UTGjY">type-II superconductors</a> which exhibit two critical magnetic fields. The first, lower critical field occurs when <a href="/facts/Abrikosov_vortex/6yP83ySP">magnetic flux vortices</a> penetrate the material but the material remains superconducting outside of these microscopic vortices. When the vortex density becomes too large, the entire material becomes non-superconducting; this corresponds to the second, higher critical field.
The ratio of the <a href="/facts/London_penetration_depth/lTmmbTS0">London penetration depth</a> λ to the <a href="/facts/Superconducting_coherence_length/DKy1eoqN">superconducting coherence length</a> ξ determines whether a superconductor is type-I or type-II. Type-I superconductors are those with 
 
 
 
 0
 <
 
 
 
 λ
 ξ
 
 
 
 <
 
 
 
 1
 
 2
 
 
 
 
 
 
 {\displaystyle 0<{\tfrac {\lambda }{\xi }}<{\tfrac {1}{\sqrt {2}}}}
 
, and type-II superconductors are those with 
 
 
 
 
 
 
 λ
 ξ
 
 
 
 >
 
 
 
 1
 
 2
 
 
 
 
 
 
 {\displaystyle {\tfrac {\lambda }{\xi }}>{\tfrac {1}{\sqrt {2}}}}
 
.

Type-I superconductor open-in-new

Type-I superconductor