Observation of the external-ac-current-induced dc voltage proportional to the steady current in superconducting loops

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.…”

“…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. Here we present experimental results obtained at measurements of the rings with asymmetric link-up of current leads.…”

“…Moreover, a ring, unlike the atom, can be produced in various forms and we can connect the current leads to it. 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 Meissner effect puzzle and the quantum force in superconductor

“…The dc voltage oscillations V dc (Φ/Φ 0 ) ∝ I p (Φ/Φ 0 ) were observed already on the ring-halves with different sections s w > s n when the asymmetric ring is switched between superconducting and normal states by ac electrical current [13,14] or a noise [8,9,12,15]. These paradoxical observations of the circular electrical current I p flowing against the dc electrical field E = − ▽ V dc in one of the ring-halves can not be explained also without the quantum force.…”

“…Little and R. D. Parks [7] at measurements of the resistance of thin cylinder in the temperature region corresponding to its superconducting resistive transition. Later on, the quantum oscillations of the ring resistance ∆R ∝ I 2 p [8,9], its magnetic susceptibility ∆Φ Ip = LI p [10], the critical current I c (Φ/Φ 0 ) = I c0 − 2|I p (Φ/Φ 0 )| [11] and the dc voltage V dc (Φ/Φ 0 ) ∝ I p (Φ/Φ 0 ) measured on segments of asymmetric rings [8,9,[12][13][14][15] were observed.…”