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Giant paramagnetic Meissner effect in multiband superconductors.

da Silva RM, Milošević MV, Shanenko AA, Peeters FM, Aguiar JA - Sci Rep (2015)

Bottom Line: Superconductors, ideally diamagnetic when in the Meissner state, can also exhibit paramagnetic behavior due to trapped magnetic flux.Here we show that in multiband superconductors paramagnetic response can be observed even in slab geometries, and can be far larger than any previous estimate - even multiply larger than the diamagnetic Meissner response for the same applied magnetic field.We link the appearance of this giant paramagnetic response to the broad crossover between conventional Type-I and Type-II superconductors, where Abrikosov vortices interact non-monotonically and multibody effects become important, causing unique flux configurations and their locking in the presence of surfaces.

View Article: PubMed Central - PubMed

Affiliation: Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Jorn. Aníbal Fernandes, s/n, 50670-901 Recife-PE, Brazil.

ABSTRACT
Superconductors, ideally diamagnetic when in the Meissner state, can also exhibit paramagnetic behavior due to trapped magnetic flux. In the absence of pinning such paramagnetic response is weak, and ceases with increasing sample thickness. Here we show that in multiband superconductors paramagnetic response can be observed even in slab geometries, and can be far larger than any previous estimate - even multiply larger than the diamagnetic Meissner response for the same applied magnetic field. We link the appearance of this giant paramagnetic response to the broad crossover between conventional Type-I and Type-II superconductors, where Abrikosov vortices interact non-monotonically and multibody effects become important, causing unique flux configurations and their locking in the presence of surfaces.

No MeSH data available.


Related in: MedlinePlus

(a) The boundaries between different types of superconductivity in the (v1/v2,T) plane, for other parameters as in Fig. 2.  line marks the onset of long-range attraction between vortices. At Hc(T) = Hc2(T) line, the mixed state vanishes in the bulk material. Dashed line shows where the energy of the superconductor-normal metal interface (σSN) changes sign. Arrow shows the path to obtain the sequence of magnetization curves shown in panel (b), for v1/v2 = 0.55 and varied temperature. Distinct changes in M(H) loops are found when either curve in panel (a) is crossed.
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f4: (a) The boundaries between different types of superconductivity in the (v1/v2,T) plane, for other parameters as in Fig. 2. line marks the onset of long-range attraction between vortices. At Hc(T) = Hc2(T) line, the mixed state vanishes in the bulk material. Dashed line shows where the energy of the superconductor-normal metal interface (σSN) changes sign. Arrow shows the path to obtain the sequence of magnetization curves shown in panel (b), for v1/v2 = 0.55 and varied temperature. Distinct changes in M(H) loops are found when either curve in panel (a) is crossed.

Mentions: Based on Fig. 3, we argue that the giant paramagnetic response is characteristic for superconductors between conventional Type-I and Type-II39. Namely, this pronounced paramagnetic response is exactly found for sample parameters between the line Hc(T) = Hc2(T) and the line where long-range vortex interaction changes sign (determined by effective GL parameter κ* calculated after Ref. [28]), with a maximum found close to the parametric line where surface energy (σSN) of the superconductor-normal metal (S-N) interface changes sign (determining the change in the polarity of the short-range vortex interaction28). For the microscopic parameters considered here, we show this domain in Fig. 4(a), as a function of v1/v2 and temperature. To test our hypothesis further, we calculated an additional set of M(H) loops, shown in Fig. 4(b), for fixed v1/v2 = 0.55 and varied temperature indicated by yellow arrow in Fig. 4(a). From Fig. 4(b), we confirmed exactly the same behavior of the loops and relationship of the giant paramagnetic response (GPR) with the delimiting lines of the critical domain: for T ≥ 0.98Tc the expected response of a Type-II slab is found, for 0.98Tc > T > 0.91Tc the paramagnetic response in decreasing field increases when crossing the long-range vortex attraction line, and finally a pronounced paramagnetic response followed by a jump to the Meissner state is observed when crossing the σSN = 0 line. Besides being useful for reaffirming our conclusions, this temperature dependence of the GPR can also be directly verifiable experimentally. Here, the considered samples are ideally clean, but even in realistic samples where flux trapping is present even at zero field, the rise and fall of GPR as a function of temperature will be easily observable in the above discussed scenario. Note that in general, changing any of the parameters can drive the in silico material across the crossover between the types of superconductivity, and thereby change the paramagnetic response. GPR is only sensitive on the regime of superconductivity the material is in, i.e., where the taken parameter set lies in the reconstructed Fig. 4(a) - Type-I, Type-II superconductivity, or in between.


Giant paramagnetic Meissner effect in multiband superconductors.

da Silva RM, Milošević MV, Shanenko AA, Peeters FM, Aguiar JA - Sci Rep (2015)

(a) The boundaries between different types of superconductivity in the (v1/v2,T) plane, for other parameters as in Fig. 2.  line marks the onset of long-range attraction between vortices. At Hc(T) = Hc2(T) line, the mixed state vanishes in the bulk material. Dashed line shows where the energy of the superconductor-normal metal interface (σSN) changes sign. Arrow shows the path to obtain the sequence of magnetization curves shown in panel (b), for v1/v2 = 0.55 and varied temperature. Distinct changes in M(H) loops are found when either curve in panel (a) is crossed.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525483&req=5

f4: (a) The boundaries between different types of superconductivity in the (v1/v2,T) plane, for other parameters as in Fig. 2. line marks the onset of long-range attraction between vortices. At Hc(T) = Hc2(T) line, the mixed state vanishes in the bulk material. Dashed line shows where the energy of the superconductor-normal metal interface (σSN) changes sign. Arrow shows the path to obtain the sequence of magnetization curves shown in panel (b), for v1/v2 = 0.55 and varied temperature. Distinct changes in M(H) loops are found when either curve in panel (a) is crossed.
Mentions: Based on Fig. 3, we argue that the giant paramagnetic response is characteristic for superconductors between conventional Type-I and Type-II39. Namely, this pronounced paramagnetic response is exactly found for sample parameters between the line Hc(T) = Hc2(T) and the line where long-range vortex interaction changes sign (determined by effective GL parameter κ* calculated after Ref. [28]), with a maximum found close to the parametric line where surface energy (σSN) of the superconductor-normal metal (S-N) interface changes sign (determining the change in the polarity of the short-range vortex interaction28). For the microscopic parameters considered here, we show this domain in Fig. 4(a), as a function of v1/v2 and temperature. To test our hypothesis further, we calculated an additional set of M(H) loops, shown in Fig. 4(b), for fixed v1/v2 = 0.55 and varied temperature indicated by yellow arrow in Fig. 4(a). From Fig. 4(b), we confirmed exactly the same behavior of the loops and relationship of the giant paramagnetic response (GPR) with the delimiting lines of the critical domain: for T ≥ 0.98Tc the expected response of a Type-II slab is found, for 0.98Tc > T > 0.91Tc the paramagnetic response in decreasing field increases when crossing the long-range vortex attraction line, and finally a pronounced paramagnetic response followed by a jump to the Meissner state is observed when crossing the σSN = 0 line. Besides being useful for reaffirming our conclusions, this temperature dependence of the GPR can also be directly verifiable experimentally. Here, the considered samples are ideally clean, but even in realistic samples where flux trapping is present even at zero field, the rise and fall of GPR as a function of temperature will be easily observable in the above discussed scenario. Note that in general, changing any of the parameters can drive the in silico material across the crossover between the types of superconductivity, and thereby change the paramagnetic response. GPR is only sensitive on the regime of superconductivity the material is in, i.e., where the taken parameter set lies in the reconstructed Fig. 4(a) - Type-I, Type-II superconductivity, or in between.

Bottom Line: Superconductors, ideally diamagnetic when in the Meissner state, can also exhibit paramagnetic behavior due to trapped magnetic flux.Here we show that in multiband superconductors paramagnetic response can be observed even in slab geometries, and can be far larger than any previous estimate - even multiply larger than the diamagnetic Meissner response for the same applied magnetic field.We link the appearance of this giant paramagnetic response to the broad crossover between conventional Type-I and Type-II superconductors, where Abrikosov vortices interact non-monotonically and multibody effects become important, causing unique flux configurations and their locking in the presence of surfaces.

View Article: PubMed Central - PubMed

Affiliation: Programa de Pós-Graduação em Ciência dos Materiais, Universidade Federal de Pernambuco, Av. Jorn. Aníbal Fernandes, s/n, 50670-901 Recife-PE, Brazil.

ABSTRACT
Superconductors, ideally diamagnetic when in the Meissner state, can also exhibit paramagnetic behavior due to trapped magnetic flux. In the absence of pinning such paramagnetic response is weak, and ceases with increasing sample thickness. Here we show that in multiband superconductors paramagnetic response can be observed even in slab geometries, and can be far larger than any previous estimate - even multiply larger than the diamagnetic Meissner response for the same applied magnetic field. We link the appearance of this giant paramagnetic response to the broad crossover between conventional Type-I and Type-II superconductors, where Abrikosov vortices interact non-monotonically and multibody effects become important, causing unique flux configurations and their locking in the presence of surfaces.

No MeSH data available.


Related in: MedlinePlus