Upper critical field and superconductor-metal transition in ultrathin niobium films

Abstract Recent studies suggest that in disordered ultrathin films superconducting (SC) state may be intrinsically inhomogeneous. Here we investigate the nature of SC state in ultrathin Nb films, of thickness d ranging from 1.2 to 20 nm, which undergo a transition from amorphous to polycrystalline structure at the thickness $$d \simeq 3.3$$ d ≃ 3.3 nm. We show that the properties of SC state are very different in polycrystalline and amorphous films. The upper critical field ($$H_{c2}$$ H c 2 ) is orbitally limited in the first case, and paramagnetically limited in the latter. The magnetic field induced superconductor-metal transition is observed, with the critical field approximately constant or decreasing as a power-law with the film conductance in polycrystalline or amorphous films, respectively. The scaling analysis indicates distinct scaling exponents in these two types of films. Negative contribution of the SC fluctuations to conductivity exists above $$H_{c2}$$ H c 2 , particularly pronounced in amorphous films, signaling the presence of fluctuating Cooper pairs. These observations suggest the development of local inhomogeneities in the amorphous films, in the form of proximity-coupled SC islands. An usual evolution of SC correlations on cooling is observed in amorphous films, likely related to the effect of quantum fluctuations on the proximity-induced phase coherence.

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Ginzburg–Landau theory of the Abrikosov vortex state near the upper critical field

Canadian Journal of Physics ◽

10.1139/p82-038 ◽

1982 ◽

Vol 60 (3) ◽

pp. 299-303 ◽

Cited By ~ 2

Author(s):

A. E. Jacobs

Keyword(s):

Critical Field ◽

Landau Theory ◽

Upper Critical Field ◽

Vortex State ◽

Quantization Condition ◽

Abrikosov Vortex ◽

Ginzburg Landau ◽

Type Ii Superconductors ◽

Flux Quantization ◽

The Magnetic Field

A method which preserves the flux-quantization condition in all orders of perturbation theory is applied to the Ginzburg–Landau theory of type-II superconductors near the upper critical field. Expansions are obtained for the order parameter, the magnetic field, and the free energy; previous results are verified and extended to one higher order in Hc2 – Ha.

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CRITICAL FIELD AND MAGNETORESISTANCE OF SINGLE CRYSTAL TmNi2B2C

International Journal of Modern Physics B ◽

10.1142/s021797929900374x ◽

1999 ◽

Vol 13 (29n31) ◽

pp. 3715-3717 ◽

Cited By ~ 7

Author(s):

D. G. NAUGLE ◽

K. D. D. RATHNAYAKA ◽

K. CLARK ◽

P. C. CANFIELD

Keyword(s):

Magnetic Field ◽

Transition Temperature ◽

Single Crystal ◽

Critical Field ◽

Superconducting Transition Temperature ◽

Magnetic Transition ◽

Upper Critical Field ◽

Superconducting Transition ◽

Large Anisotropy ◽

The Magnetic Field

In-plane resistance as a function of magnitude and direction of the magnetic field and the temperature has been measured for TmNi2B2C from above the superconducting transition temperature at 10.7 K to below the magnetic transition TN=1.5 K. The superconducting upper critical field HC2(T) exhibits a large anisotropy and structure in the vicinity of TN. The magnetoresistance above TC is large and changes sign as the direction of the magnetic field is rotated from in-plane to parallel with the c-axis.

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Investigation of the magnetic field angle dependence of resistance, irreversibility field, upper critical field and critical current density in DC sputtered Bi-2223 thin film

Physica B Condensed Matter ◽

10.1016/j.physb.2011.02.041 ◽

2011 ◽

Vol 406 (10) ◽

pp. 1853-1857 ◽

Cited By ~ 17

Author(s):

G. Yildirim ◽

M. Akdogan ◽

S.P. Altintas ◽

M. Erdem ◽

C. Terzioglu ◽

...

Keyword(s):

Magnetic Field ◽

Thin Film ◽

Critical Current Density ◽

Critical Current ◽

Critical Field ◽

Current Density ◽

Upper Critical Field ◽

Irreversibility Field ◽

Angle Dependence ◽

The Magnetic Field

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Field Anisotropy of the Pseudogap State in Bi2Sr2CaCu2O8+y Ultrahigh Magnetic Fields

International Journal of Modern Physics B ◽

10.1142/s0217979203021460 ◽

2003 ◽

Vol 17 (18n20) ◽

pp. 3598-3603 ◽

Cited By ~ 1

Author(s):

L. Krusin-Elbaum ◽

T. Shibauchi ◽

C. H. Mielke

Keyword(s):

Magnetic Fields ◽

Critical Field ◽

Orbital Motion ◽

Upper Critical Field ◽

Large Field ◽

Cooper Pairs ◽

Spin Channel ◽

Pseudogap State ◽

Ultrahigh Magnetic Fields ◽

Small Anisotropy

The orientational anisotropy of the pseudogap closing field Hpg is investigated in magnetic fields up to 60 T applied parallel (||ab) and normal (||c) to CuO 2 planes in Bi 2 Sr 2 CaCu 2 O 8+y. We find that, in contrast to large field anisotropy related to the orbital motion of Cooper pairs below the upper critical field Hc2, the temperature-independent and small anisotropy of Hpg is due to anisotropy of the g-factor: [Formula: see text], indicating correlations only in the spin-channel.

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Evolution of the upper critical field and superconducting vortex phase with thickness in PLD-grown Ta fllms

Superconductor Science and Technology ◽

10.1088/1361-6668/ac4ba1 ◽

2022 ◽

Author(s):

Yixin Liu ◽

Han Zhang ◽

Xiaowen Han ◽

Teng Wang ◽

Lingling Wang ◽

...

Keyword(s):

Critical Field ◽

Three Dimensional ◽

Anisotropy Parameter ◽

Upper Critical Field ◽

Superconducting Devices ◽

Liquid Region ◽

Superconducting Transition ◽

Critical Fields ◽

Residual Resistance ◽

20 Nm

Abstract High quality superconducting thin films are the basis for the application of superconducting devices. Here we report the fllm growth and superconducting properties of the Ta films. The films were grown by the pulsed laser deposition technique on the α-Al2O3 substrates. It is found that, with the increase of the fllm thickness from 20 nm to 61 nm, both the superconducting transition temperature Tc and residual resistance ratio RRR display an upward trend, while the upper critical field decreases monotonously in a wide temperature region. A clear anisotropic behavior is revealed by comparing the upper critical fields with two difierent orientations (H ⊥ film and H // film). The anisotropy parameter Γ is found to be as high as 20 for the sample with the thickness of 20 nm. The systematical evolution from two- to three-dimensional features for the superconductivity with the increase of fllm thickness is observed in the temperature dependent upper critical fleld data. Moreover, the vortex liquid region tends to expand with the increase of the fllm thickness.

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DETERMINATIONS OF UPPER CRITICAL FIELDS IN CONTINUOUS GINZBURG–LANDAU MODEL

International Journal of Modern Physics C ◽

10.1142/s0129183104006297 ◽

2004 ◽

Vol 15 (06) ◽

pp. 783-807

Author(s):

L. WANG ◽

H. S. LIM ◽

C. K. ONG

Keyword(s):

Critical Field ◽

Eigenvalue Problems ◽

Upper Critical Field ◽

Critical Fields ◽

Ginzburg Landau ◽

Direction Parallel ◽

Landau Model ◽

The Magnetic Field ◽

Good Agreement

Novel procedures to determine the parallel upper critical field Bc2 (one-dimensional, 1D) have been proposed within a continuous Ginzburg–Landau model. Unlike conventional methods, where Bc2 is obtained through the determination of the smallest eigenvalue of an appropriate eigen equation, the square of the magnetic field is treated as eigenvalue problems by two procedures so that the upper critical field can be directly deduced. The two procedures proposed are extended to determine the upper critical field in the c–a crystal plane (two-dimensional, 2D) with an arbitrary angle θ tilted from the c-axis. The calculated Bc2 from the two procedures are consistent with each other in both 1D and 2D cases. Moreover, the values of Bc2 near the direction parallel to the layers obtained in the 2D case well approximate the counterparts in the 1D case. The properties of the calculated Bc2 are in reasonably good agreement with existing theories and experiments. The profiles of the order parameters associated with Bc2 for both 1D and 2D cases are Gaussian-like, further validating the methodology proposed.

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Transport Properties and Upper Critical Field of Single Crystal Non-Magnetic LuxY1-xNi2B2C and Magnetic LuxGd1-xNi2B2C

International Journal of Modern Physics B ◽

10.1142/s0217979203021265 ◽

2003 ◽

Vol 17 (18n20) ◽

pp. 3493-3495 ◽

Cited By ~ 3

Author(s):

K. D. D. Rathnayaka ◽

D. G. Naugle ◽

A. C. Dumar ◽

M. P. Anatska ◽

P. C. Canfield

Keyword(s):

Magnetic Field ◽

Thermal Conductivity ◽

Low Temperature ◽

Single Crystal ◽

Critical Field ◽

Magnetic Impurity ◽

Positive Curvature ◽

Upper Critical Field ◽

Magnetic Impurities ◽

The Magnetic Field

The in-plane resistance of single crystal non-magnetic Lu x Y 1-x Ni 2 B 2 C and magnetic Lu x Gd 1-x Ni 2 B 2 C samples as a function of the magnitude and direction of the magnetic field and temperature have been measured. The superconducting upper critical field Hc2(T) is anisotropic for both. A positive curvature in Hc2(T) near Tc(x) is clearly observed only for the non-magnetic impurity. At low temperature Hc2(T) for the sample with magnetic impurities is strongly reduced. Thermopower, thermal conductivity and resistivity as a function of temperature are also reported for Lu x Gd 1-x Ni 2 B 2 C .

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Multiband effects on the upper critical field angular dependence of 122-family iron pnictide superconductors

Scientific Reports ◽

10.1038/s41598-021-90858-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

I. F. Llovo ◽

C. Carballeira ◽

D. Sóñora ◽

A. Pereiro ◽

J. J. Ponte ◽

...

Keyword(s):

Magnetic Fields ◽

Angular Dependence ◽

Critical Field ◽

Upper Critical Field ◽

Single Band ◽

Band Model ◽

Cooper Pairs ◽

Ginzburg Landau ◽

Superconducting Fluctuations

AbstractDetailed measurements of the in-plane resistivity were performed in a high-quality Ba($$\hbox {Fe}_{1-x}\hbox {Co}_{{x}}$$ Fe 1 - x Co x )$$_2\hbox {As}_2$$ 2 As 2 ($$x=0.065$$ x = 0.065 ) single crystal, in magnetic fields up to 9 T and with different orientations $$\theta$$ θ relative to the crystal c axis. A significant $$\rho (T)_{H,\theta }$$ ρ ( T ) H , θ rounding is observed just above the superconducting critical temperature $$T_c$$ T c due to Cooper pairs created by superconducting fluctuations. These data are analyzed in terms of a generalization of the Aslamazov-Larkin approach, that extends its applicability to high reduced-temperatures and magnetic fields. This method allows us to carry out a criterion-independent determination of the angular dependence of the upper critical field, $$H_{c2}(\theta )$$ H c 2 ( θ ) . In spite of the relatively small anisotropy of this compound, it is found that $$H_{c2}(\theta )$$ H c 2 ( θ ) presents a significant deviation from the single-band 3D anisotropic Ginzburg-Landau (3D-aGL) approach, particularly for large $$\theta$$ θ (typically above $$\sim 60^o$$ ∼ 60 o ). These results are interpreted in terms of the multiband nature of these materials, in contrast with other proposals for similar $$H_{c2}(\theta )$$ H c 2 ( θ ) anomalies. Our results are also consistent with an effective anisotropy factor almost temperature independent near $$T_c$$ T c , a result that differs from the ones obtained by using a single-band model.

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