Temperature-induced crossover between<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>0</mml:mn></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi></mml:math>states in S/F/S junctions

Sellier, H.; Baraduc, C.; Lefloch, F.; Calemczuk, R.

doi:10.1103/physrevb.68.054531

Cited by 151 publications

(208 citation statements)

References 26 publications

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“…A negative sign of the real part of the order parameter may occur when the thickness of the F layer is larger than the coherence length of the F layer. The occurrence of the π-phase shift makes it possible to realize the SFS π -junctions 1 , as was confirmed experimentally 4,5,6,7,8 . The order parameter oscillations also lead to nonmonotonous dependence of T c in SF bilayers on the F-layer thickness 9,10,11,12,13 .…”

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confidence: 64%

Resonant peak in the density of states in normal-metal/diffusive-ferromagnet/superconductor junctions

2005

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The conditions for the formation of zero-energy peak in the density of states (DOS) in the normal metal / insulator / diffusive ferromagnet / insulator / s-wave superconductor (N/I/DF/I/S) junctions are studied by solving the Usadel equations. The DOS of the DF is calculated in various regimes for different magnitudes of the resistance, Thouless energy and the exchange field of the DF, as well as for various resistances of the insulating barriers. The conditions for the DOS peak are formulated for the cases of weak proximity effect (large resistance of the DF/S interface) and strong proximity effect (small resistance of the DF/S interface).In ferromagnet/superconductor (F/S) junctions Cooper pairs penetrating into the F layer from the S layer have a nonzero momentum due to the influence of exchange field 1,2,3 . This results in oscillating behavior of the pair amplitude or a π-phase shift of the order parameter in the ferromagnet. A negative sign of the real part of the order parameter may occur when the thickness of the F layer is larger than the coherence length of the F layer. The occurrence of the π-phase shift makes it possible to realize the SFS π -junctions 1 , as was confirmed experimentally 4,5,6,7,8 . The order parameter oscillations also lead to nonmonotonous dependence of T c in SF bilayers on the F-layer thickness 9,10,11,12,13 . Effects of resonant transmission in conductivity of SF structures were discussed in Ref 14,15,16 .Another interesting consequence of the oscillations of the pair amplitude is the spatially damped oscillating behavior of the density of states (DOS) in a ferromagnet predicted theoretically 17,18,19,20 in various regimes. The energy dependent DOS calculated in the clean 18 and the dirty 21 limits exhibits rich structures. Experimentally DOS in F/S bilayers was measured by Kontos et al. who found a broad DOS peak around zero energy when the π-phase shift occurs 22 . In diffusive ferromagnet/superconductor (DF/S) junctions the zeroenergy DOS may have a sharp peak 21 . However the conditions for the appearance of such anomaly have not been studied systematically so far.The purpose of the present paper is to calculate DOS in N/DF/S junctions and to formulate the conditions for the zero-energy DOS peak in two regimes corresponding to the weak proximity effect (large DF/S interface resistance) and strong proximity effect (small DF/S interface resistance). We will show that in the former case the condition is equivalent to the one of Ref. 21 , while in the latter case the new condition is found. The calculation will be performed in the zero-temperature regime by varying the interface resistances as well as the resistance, the exchange field and the Thouless energy of the DF layer.We consider a junction consisting of normal and superconducting reservoirs connected by a quasi-onedimensional diffusive ferromagnet conductor (DF) with a resistance R d and a length L much larger than the mean free path. The DF/N interface located at x = 0 has the resistance R ′ b , while the DF/S interface...

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confidence: 64%

Resonant peak in the density of states in normal-metal/diffusive-ferromagnet/superconductor junctions

2005

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“…The sputtering conditions were identical to that of Ref. [7], where Nb/CuNi/Nb junctions critical current was studied. The Nb layer thickness of 200 nm (at the wafer center) was chosen to be much larger than the GinzburgLandau coherence length which is estimated to be 12 nm.…”

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confidence: 99%

Scanning tunneling spectroscopy of the superconducting proximity effect in a diluted ferromagnetic alloy

et al. 2005

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We studied the proximity effect between a superconductor (Nb) and a diluted ferromagnetic alloy (CuNi) in a bilayer geometry. We measured the local density of states on top of the ferromagnetic layer, which thickness varies on each sample, with a very low temperature Scanning Tunneling Microscope. The measured spectra display a very high homogeneity. The analysis of the experimental data shows the need to take into account an additional scattering mechanism. By including in the Usadel equations the effect of the spin relaxation in the ferromagnetic alloy, we obtain a good description of the experimental data.

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“…13,14 These π -shifts lead to negatively biased critical current density, j c , and anomalous Josephson properties of sequences of 0 -π biased tunnel junctions. 15,16,17,18,19,20 The observed anomalies are especially significant if the lengths of 0 -and π -fragments are much less than the Josephson penetration depth λ J defined by the spatial average of |j c |. 21,22,23,24 Thus, several qualitative explanations have been put forward to understand the physics of fractional Shapiro steps.…”

Section: Introductionmentioning

confidence: 99%

Shapiro steps in Josephson junctions with alternating critical current density

Moshe

Mint︠s︡

2007

Phys. Rev. B

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We treat theoretically Shapiro steps in tunnel Josephson junctions with spatially alternating critical current density. Explicit analytical formulas for the width of the first integer (normal) and half-integer (anomalous) Shapiro steps are derived for short junctions. We develop coarse-graining approach, which describes Shapiro steps in the voltage-current curves of the asymmetric grain boundaries in YBCO thin films and different superconductor-ferromagnet-superconductor Josephson-type heterostructures.

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Temperature-induced crossover between0andπstates in S/F/S junctions

Cited by 151 publications

References 26 publications

Resonant peak in the density of states in normal-metal/diffusive-ferromagnet/superconductor junctions

Resonant peak in the density of states in normal-metal/diffusive-ferromagnet/superconductor junctions

Scanning tunneling spectroscopy of the superconducting proximity effect in a diluted ferromagnetic alloy

Shapiro steps in Josephson junctions with alternating critical current density

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