The temperature dependence of the anisotropy parameter of upper critical field γHe2 （T） = Hc2^‖ （T） /Hc2^⊥ （T） and London penetration depth γλ （T） = λ‖（T）/λ⊥ （T） are calculated using two-band Ginz...The temperature dependence of the anisotropy parameter of upper critical field γHe2 （T） = Hc2^‖ （T） /Hc2^⊥ （T） and London penetration depth γλ （T） = λ‖（T）/λ⊥ （T） are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γHc2 （T） is increased, while the London penetration depth anisotropy γλ（T） reveals an opposite behavior. Results of our calculations are in agreement with experimental data for single crystal MgB2 and with other calculations..Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented.展开更多
In the anisotropic Ginzburg-Landau theory, which is the most commonly applied phenomenological description of layered superconductors, the anisotropy is described by the temperature independent effective mass anisotro...In the anisotropic Ginzburg-Landau theory, which is the most commonly applied phenomenological description of layered superconductors, the anisotropy is described by the temperature independent effective mass anisotropy. However, a temperature dependent anisotropy was observed in some superconductors, especially in MgB2 [1], and was explained as a consequence of the presence of two superconducting gaps. A similar temperature dependence was also observed in iron-based superconductors [2, 3], in which an evidence for two-band superconductivity was provided by several experiments, including point contact spectroscopy and ARPES. Furthermore, it was found that, the in-plane magnetic penetration depth related to the superconducting carrier density increases with increasing magnetic field due to a partial suppression of the energy gap [4]. A recent study of the cupra^e superconductor SmBa2Cu307-fi [5] has shown that the temperature dependence of the anisotropy is observed also for this class of the layered high-To superconductors. Temperature variation of the anisotropy strongly depends on the doping level and is more pronounced for the samples with lower oxygen content, i.e., for the samples with well-developed pseudogap. Very recently the weak temperature dependence of the out-of-plane anisotropy parameter for overdoped YBa2Cu307 single crystal was found too [6]. It was suggested that such dependence of anisotropy parameter may indicate the presence of two energy scales in the superconducting behavior, related to multigap superconductivity or one-gap superconductivity with a pseudogap. This rises the question whether the temperature dependence of the anisotropy is a common property of all layered high-To superconductors and how it is linked to the gap structure. Importantly, besides superconductivity, various iron-based compounds exhibit coexisting magnetic order. This order can be influenced by an external magnetic field [7], making iron-based superconductors a fascinating template for magnetic-field tuned applicatio展开更多
文摘The temperature dependence of the anisotropy parameter of upper critical field γHe2 （T） = Hc2^‖ （T） /Hc2^⊥ （T） and London penetration depth γλ （T） = λ‖（T）/λ⊥ （T） are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γHc2 （T） is increased, while the London penetration depth anisotropy γλ（T） reveals an opposite behavior. Results of our calculations are in agreement with experimental data for single crystal MgB2 and with other calculations..Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented.
文摘In the anisotropic Ginzburg-Landau theory, which is the most commonly applied phenomenological description of layered superconductors, the anisotropy is described by the temperature independent effective mass anisotropy. However, a temperature dependent anisotropy was observed in some superconductors, especially in MgB2 [1], and was explained as a consequence of the presence of two superconducting gaps. A similar temperature dependence was also observed in iron-based superconductors [2, 3], in which an evidence for two-band superconductivity was provided by several experiments, including point contact spectroscopy and ARPES. Furthermore, it was found that, the in-plane magnetic penetration depth related to the superconducting carrier density increases with increasing magnetic field due to a partial suppression of the energy gap [4]. A recent study of the cupra^e superconductor SmBa2Cu307-fi [5] has shown that the temperature dependence of the anisotropy is observed also for this class of the layered high-To superconductors. Temperature variation of the anisotropy strongly depends on the doping level and is more pronounced for the samples with lower oxygen content, i.e., for the samples with well-developed pseudogap. Very recently the weak temperature dependence of the out-of-plane anisotropy parameter for overdoped YBa2Cu307 single crystal was found too [6]. It was suggested that such dependence of anisotropy parameter may indicate the presence of two energy scales in the superconducting behavior, related to multigap superconductivity or one-gap superconductivity with a pseudogap. This rises the question whether the temperature dependence of the anisotropy is a common property of all layered high-To superconductors and how it is linked to the gap structure. Importantly, besides superconductivity, various iron-based compounds exhibit coexisting magnetic order. This order can be influenced by an external magnetic field [7], making iron-based superconductors a fascinating template for magnetic-field tuned applicatio
