Explain the concept of the two junctions in detail and also list out the differences between the two
Josephson effects.
Answers
Answer:
The Josephson effect is the phenomenon of supercurrent, a current that flows indefinitely long without any voltage applied, across a device known as a Josephson junction (JJ), which consists of two or more superconductors coupled by a weak link. The weak link can consist of a thin insulating barrier (known as a superconductor–insulator–superconductor junction, or S-I-S), a short section of non-superconducting metal (S-N-S), or a physical constriction that weakens the superconductivity at the point of contact (S-s-S).
The Josephson effect is an example of a macroscopic quantum phenomenon. It is named after the British physicist Brian David Josephson, who predicted in 1962 the mathematical relationships for the current and voltage across the weak link. The DC Josephson effect had been seen in experiments prior to 1962, but had been attributed to "super-shorts" or breaches in the insulating barrier leading to the direct conduction of electrons between the superconductors. The first paper to claim the discovery of Josephson's effect, and to make the requisite experimental checks, was that of Philip Anderson and John Rowell. These authors were awarded patents on the effects that were never enforced, but never challenged.
Before Josephson's prediction, it was only known that normal (i.e. non-superconducting) electrons can flow through an insulating barrier, by means of quantum tunneling. Josephson was the first to predict the tunneling of superconducting Cooper pairs. For this work, Josephson received the Nobel Prize in Physics in 1973. Josephson junctions have important applications in quantum-mechanical circuits, such as SQUIDs, superconducting qubits, and RSFQ digital electronics. The NIST standard for one volt is achieved by an array of 20,208 Josephson junctions in series.
Answer:
Explanation:In a Josephson junction, the nonsuperconducting barrier separating the two superconductors must be very thin. ... This in turn causes a lowering of the junction's critical current, causing even more normal current to flow--and a larger AC voltage. LOGIC CIRCUITS for computers have been fabricated from Josephson junctions.
In the a.c. Josephson effect, a constant chemical potential difference (voltage) is applied, which causes an oscillating current to flow through the barrier. ... In the d.c. Josephson effect, a small constant current is applied, resulting in a constant supercurrent flowing through the barrier.
The inverse AC Josephson effect
Microwave radiation of a single (angular) frequency {\displaystyle \omega }\omega can induce quantized DC voltages[14] across the Josephson junction, in which case the Josephson phase takes the form {\displaystyle \varphi (t)=\varphi _{0}+n\omega t+a\sin(\omega t)}{\displaystyle \varphi (t)=\varphi _{0}+n\omega t+a\sin(\omega t)}, and the voltage and current across the junction will be:
{\displaystyle V(t)={\frac {\hbar }{2e}}\omega (n+a\cos(\omega t)),{\text{ and }}I(t)=I_{c}\sum _{m=-\infty }^{\infty }J_{m}(a)\sin(\varphi _{0}+(n+m)\omega t),}{\displaystyle V(t)={\frac {\hbar }{2e}}\omega (n+a\cos(\omega t)),{\text{ and }}I(t)=I_{c}\sum _{m=-\infty }^{\infty }J_{m}(a)\sin(\varphi _{0}+(n+m)\omega t),}
The DC components are:
{\displaystyle V_{DC}=n{\frac {\hbar }{2e}}\omega ,{\text{ and }}I_{DC}=I_{c}J_{-n}(a)\sin \varphi _{0}.}{\displaystyle V_{DC}=n{\frac {\hbar }{2e}}\omega ,{\text{ and }}I_{DC}=I_{c}J_{-n}(a)\sin \varphi _{0}.}