Multiple superconducting ring ratchets for ultrasensitive detection of non-equilibrium noises

Abstract

Magnetic quantum periodicity in the dc voltage is observed when asymmetric rings are switched between superconducting and normal state by a noise or ac current. This quantum effect is used for detection of a non-equilibrium noise with the help of a system of 667 asymmetric aluminum rings of 1 µm in diameter connected in series. Any noise down to the equilibrium one can be detected with the help of such system with enough great number of asymmetric rings.

Experimental investigations of the problem of the quantum jump with the help of superconductor nanostructures

“…The two state n = n ′ and n = n ′ + 1 have the same value of the kinetic energy in (7) E k = (nΦ 0 − Φ) 2 /2L k = Φ 2 0 /8L k at Φ = (n ′ + 0.5)Φ 0 . According to the universally recognized explanation [33] the quantum periodicity in the transition temperature [20], the ring resistance [24,27], the magnetic susceptibility [23], the dc voltage [21,22,28,29] and the critical current [25,26,30] are observed due to the change of the quantum number n with the magnetic flux at Φ = (n ′ + 0.5)Φ 0 .…”

Quantum periodicity in the critical current of superconducting rings with asymmetric link-up of current leads

“…The persistent current (3) decreases by jump [20,21] at |n − Φ/Φ 0 | ≈ r/ √ 3ξ(T ) due to the velocity (3a) jump with the change of the winding number n. According to the requirement l dl∇ϕ = n2π the n change occurs due to phase slip [22] when the ring or a ring segment is switched in normal state, from n s = 2n s0 /3 to n s = 0, for a while. The winding number n corresponds to the minimum of the kinetic energy (4) with predominant probability P n ∝ exp −E k (n)/k B T when the ring is switched in normal state by an external current [9][10][11], noise [6,12,14,23], or thermal fluctuations [1, 13,24]. Therefore the quantum periodicity in the critical current [9,10], in the dc voltage [6,11,12,14,23], in the resistance [1,13] and in the magnetic susceptibility [24] is observed.…”

“…As a consequence the resistance ∆R(Φ) ∝ −∆T c /T c measured in the fluctuation region near the transition temperature T ≈ T c , where the resistance changes from R = 0 at T < T c to R = R n at T > T c , has the maximums at Φ = (n ′ + 0.5)Φ 0 and the minimums at Φ = n ′ Φ 0 [1, 12,13]. The quantum oscillations of the magnetic susceptibility ∆Φ Ip measured in the fluctuation region near T c [24] and the dc voltage V dc (Φ) [6,11,12,14,23] are alternating because of their proportionality ∆Φ Ip = L f I p [24] and V dc (Φ) ∝ I p (Φ) to the persistent current f sw is the frequency of rings switching between superconducting and normal states. The values ∆Φ Ip and (4) and thus the probability P n ′ = P n ′ +1 at Φ = (n ′ + 0.5)Φ 0 .…”

“…Measurements of the critical current [9,10] and other parameters [10][11][12][13] of asymmetric superconducting rings with the help of the current leads have allowed to discover a new quantum phenomenon and to reveal some contradictions between theoretical predictions and experimental results. The rectification effect discovered due to these measurements allows to use a system with large number of asymmetric rings for ultrasensitive detection of non-equilibrium noises [6] and for the experimental investigation of the possibility of observing persistent voltage [14]. The rings investigated formerly [9][10][11][12][13][14] were asymmetric due to different cross-section of their halves.…”

Development of a Superconducting Differential Double Contour Interferometer

“…The observation of these jumps has the critical importance for the opportunity to use the DDCI for high sensitive detection of magnetic flux. The conventional theory [7] and numerous experiments [9,10,[12][13][14][15] testify to the sharpness of the change of the probability P (n) of the n state of superconducting loop with enough big value of the persistent current I p,A . The theory predicts the jump of the critical current with the n change at Φ = (n + 0.5)Φ 0 not only of the double contour interferometer but also, for example, of a superconducting ring with asymmetric link-up of current leads.…”