Nonlinear 
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 characteristics of two-dimensional superconductors: Berezinskii-Kosterlitz-Thouless physics versus inhomogeneity

Venditti, G.; Biscaras, Johan; Hurand, S.; Bergeal, N.; Lesueur, J.; Dogra, Anjana; Budhani, R. C.; Mondal, Mintu; Jesudasan, John; Raychaudhuri, Pratap; Caprara, S.; Benfatto, Lara

doi:10.1103/physrevb.100.064506

Cited by 32 publications

(50 citation statements)

References 76 publications

(118 reference statements)

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“…The BKT behaviour suggests that the superconductivity of FeSe is quasi-two dimensional and this can be a general signature of multi-band ironbased superconductors where 2D fluctuations can be responsible for the suppression of superconductivity. The lack of the sudden jump in α at T BKT and the non-linear IV behaviour has been found in other thin films of conventional superconductors, where the disorder smears out the sharp features 35 . In our FeSe devices local inhomogeneities caused by the formation of structural domains at temperatures below the nematic transition can lead to an increase in the width of the superconducting transition.…”

Section: Thickness Dependence Of the Transport Behaviour Of Fese Thinmentioning

confidence: 58%

Suppression of superconductivity and enhanced critical field anisotropy in thin flakes of FeSe

et al. 2020

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FeSe is a unique superconductor that can be manipulated to enhance its superconductivity using different routes, while its monolayer form grown on different substrates reaches a record high temperature for a two-dimensional system. In order to understand the role played by the substrate and the reduced dimensionality on superconductivity, we examine the superconducting properties of exfoliated FeSe thin flakes by reducing the thickness from bulk down towards 9 nm. Magnetotransport measurements performed in magnetic fields up to 16 T and temperatures down to 2 K help to build up complete superconducting phase diagrams of different thickness flakes. While the thick flakes resemble the bulk behaviour, by reducing the thickness the superconductivity of FeSe flakes is suppressed. The observation of the vortex-antivortex unbinding transition in different flakes provide a direct signature of a dominant two-dimensional pairing channel. However, the upper critical field reflects the evolution of the multi-band nature of superconductivity in FeSe becoming highly two-dimensional and strongly anisotropic only in the thin limit. Our study provides detailed insights into the evolution of the superconducting properties of a multi-band superconductor FeSe in the thin limit in the absence of a dopant substrate.

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Section: Thickness Dependence Of the Transport Behaviour Of Fese Thinmentioning

confidence: 58%

Suppression of superconductivity and enhanced critical field anisotropy in thin flakes of FeSe

et al. 2020

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“…The T C, 0 and T C,on of 0.2 wt% Y 2 O 3 :Eu 3+ +Ag-doped sample (A5) are higher than 0.3% Y 2 O 3 :Eu 3+ +Ag-doped sample (A6). All the R-T curves display characteristic behavior of a percolative transition [ 46 , 47 , 48 ]; the present experimental results can be explained by observing a broad percolative transition [ 49 , 50 ]. In the percolative transition, the T C,on is related to some regions where the T C is higher than the average T C , and these regions match the T C of Bi2223.…”

Section: Resultsmentioning

confidence: 88%

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content

Chen

Wang

et al. 2021

Nanomaterials

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A smart meta-superconductor Bi(Pb)SrCaCuO (B(P)SCCO) may increase the critical transition temperature (TC) of B(P)SCCO by electroluminescence (EL) energy injection of inhomogeneous phases. However, the increase amplitude ΔTC (ΔTC=TC−TC,pure) of TC is relatively small. In this study, a smart meta-superconductor B(P)SCCO with different matrix sizes was designed. Three kinds of raw materials with different particle sizes were used, and different series of Y2O3:Sm3+, Y2O3, Y2O3:Eu3+, and Y2O3:Eu3++Ag-doped samples and pure B(P)SCCO were prepared. Results indicated that the TC of the Y2O3 or Y2O3:Sm3+ non-luminescent dopant doping sample is lower than that of pure B(P)SCCO. However, the TC of the Y2O3:Eu3++Ag or Y2O3:Eu3+ luminescent inhomogeneous phase doping sample is higher than that of pure B(P)SCCO. With the decrease of the raw material particle size from 30 to 5 μm, the particle size of the B(P)SCCO superconducting matrix in the prepared samples decreases, and the doping content of the Y2O3:Eu3++Ag or Y2O3:Eu3+ increases from 0.2% to 0.4%. Meanwhile, the increase of the inhomogeneous phase content enhances the ΔTC. When the particle size of raw material is 5 μm, the doping concentration of the luminescent inhomogeneous phase can be increased to 0.4%. At this time, the zero-resistance temperature and onset transition temperature of the Y2O3:Eu3++Ag doped sample are 4 and 6.3 K higher than those of pure B(P)SCCO, respectively.

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“…The advantage of choosing an additional potential term of the form in Eqs. 20, (21) is that it is a local term, it is derivable with respect to the phase difference, and it has a direct physical interpretation in terms of currents. For μ = 0 one recovers the classical XY Hamiltonian (2) while for μ > 0 the additional potential term favours the presence of spin currents in the system.…”

Section: The Modified Xy Modelmentioning

confidence: 99%

“…At the same time, interesting new issues appeared also in conventional superconducting (SC) films. For instance, the spatial inhomogeneity of the superconducting order parameter has been observed to become more pronounced near the superconducting-insulator transition (SIT) [17,18], raising the question of its effect on the BKT phase transition [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Interplay of spin waves and vortices in the two-dimensional XY model at small vortex-core energy

et al. 2020

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The Berezinskii-Kosterlitz-Thouless (BKT) mechanism describes universal vortex unbinding in many twodimensional systems, including the paradigmatic XY model. However, most of these systems present a complex interplay between excitations at different length scales that complicates theoretical calculations of nonuniversal thermodynamic quantities. These difficulties may be overcome by suitably modifying the initial conditions of the BKT flow equations to account for noncritical fluctuations at small length scales. In this work, we perform a systematic study of the validity and limits of this two-step approach by constructing optimised initial conditions for the BKT flow. We find that the two-step approach can accurately reproduce the results of Monte Carlo simulations of the traditional XY model. To systematically study the interplay between vortices and spin-wave excitations, we introduce a modified XY model with increased vortex fugacity. We present large-scale Monte Carlo simulations of the spin stiffness and vortex density for this modified XY model and show that even at large vortex fugacity, vortex unbinding is accurately described by the nonperturbative functional renormalization group.

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Nonlinear I−V characteristics of two-dimensional superconductors: Berezinskii-Kosterlitz-Thouless physics versus inhomogeneity

Cited by 32 publications

References 76 publications

Suppression of superconductivity and enhanced critical field anisotropy in thin flakes of FeSe

Suppression of superconductivity and enhanced critical field anisotropy in thin flakes of FeSe

Relationship between the TC of Smart Meta-Superconductor Bi(Pb)SrCaCuO and Inhomogeneous Phase Content

Interplay of spin waves and vortices in the two-dimensional XY model at small vortex-core energy

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