Theory of Tunneling Spectroscopy of Multi-Band Superconductors

Burmistrova, A. V.; Devyatov, I. A.; Golubov, Alexandre Avraamovitch; Yada, Keiji; Tanaka, Yukio

doi:10.7566/jpsj.82.034716

Cited by 27 publications

(39 citation statements)

References 88 publications

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“…Due to the necessity to take into account at least two orbitals for correct description of the FeBS band structure, two hopping parameters γ 1 and γ 2 should be introduced in orbital space which describe an interface between single-band and two-band materials (instead of single hopping parameter γ at the interface between two single-band materials 42 ). The introduction of these two parameters provides a possibility to match coherently wave functions (Green functions) at this boundary and to describe the processes of interband scaterring microscopically, as it was demonstrated in 23,24 For simplicity, we assume that the lattice constants in S, I and S p are equal. To calculate the Josephson current across S/I/S p junction we should construct Green's functions of the whole system.…”

Section: Model For the Contact Between S-wave Superconductor Andmentioning

confidence: 99%

“…(3) -(5) can be obtained from matching the Green's functions (3) -(5) at the S/I and I/S interfaces. The boundary conditions for multiorbital metals in tight-binding approximation have been proposed recently 23,24 . For temperature Green's functions, these boundary conditions in the quasiclassical approximation at S/I boundary have the form:…”

Section: A Model Of S/i/s Josephson Junctionmentioning

confidence: 99%

“…It is necessary to note that the same results as described above can be obtained not only in terms of Green's functions but also in terms of wave functions 37 . For this purpose one should solve Bogoliubov-de Gennes equations and find wave functions for a s-wave superconductor, an insulating region and a d-wave superconductor on the sites of the descrete lattice 24 . However, calculations of the total Josephson current in terms of wave functions are inconvenient for the averaging of the Josephson current over all possible values of k y than in terms of Green's functions and lead to numerical errors.…”

Section: B Model Of S/i/s D Josephson Junctionmentioning

confidence: 99%

“…Several phenomenological theories of transport in junctions based on FeBS have been proposed in the past [16][17][18][19][20][21][22] . However, only recently a microscopic theory of the quasiparticle current in normal metal -multiband superconductor junctions was formulated 23,24 , which takes into account unusual properties of these materials. But there is still no microscopic theory to describe the Josephson current in junctions between multiband superconductor and conventional single-band spin-singlet s-wave superconductor, which goes beyond the existing phenomenological theories 18,[25][26][27] .…”

Section: Introductionmentioning

confidence: 99%

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Josephson current in Fe-based superconducting junctions: Theory and experiment

et al. 2015

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We present theory of dc Josephson effect in contacts between Fe-based and spin-singlet s-wave superconductors. The method is based on the calculation of temperature Green's function in the junction within the tight-binding model. We calculate the phase dependencies of the Josephson current for different orientations of the junction relative to the crystallographic axes of Fe-based superconductor. Further, we consider the dependence of the Josephson current on the thickness of an insulating layer and on temperature. Experimental data for PbIn/Ba1−xKx(FeAs)2 pointcontact Josephson junctions are consistent with theoretical predictions for s± symmetry of an order parameter in this material. The proposed method can be further applied to calculations of the dc Josephson current in contacts with other new unconventional multiorbital superconductors, such as Sr2RuO4 and superconducting topological insulator CuxBi2Se3.

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Section: Model For the Contact Between S-wave Superconductor Andmentioning

confidence: 99%

Section: A Model Of S/i/s Josephson Junctionmentioning

confidence: 99%

Section: B Model Of S/i/s D Josephson Junctionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Josephson current in Fe-based superconducting junctions: Theory and experiment

et al. 2015

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“…of Eq. (61) 58,59 the BCs at an interface between different materials in a ballistic case were derived using another approach.…”

Section: Subgap Conductance In N/i Sf /S Junctions: Effective Boumentioning

confidence: 99%

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

2012

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We present a theoretical study of the quasiparticle and subgap conductance of generic X/I sf /S M junctions with a spin-filter barrier I sf , where X is either a normal N or a ferromagnetic metal F and S M is a superconductor with a built-in exchange field. Our study is based on the tunneling Hamiltonian and the Green's-function technique. First, we focus on the quasiparticle transport, both above and below the superconducting critical temperature. We obtain a general expression for the tunneling conductance which is valid for arbitrary values of the exchange field and arbitrary magnetization directions in the electrodes and in the spin-filter barrier. In the second part, we consider the subgap conductance of a N/I sf /S junction, where S is a conventional superconductor. In order to account for the spin-filter effect at interfaces, we heuristically derive boundary conditions for the quasiclassical Green's functions. With the help of these boundary conditions, we show that the proximity effect and the subgap conductance are suppressed by spin filtering in a N/I sf /S junction. Our work provides useful tools for the study of spin-polarized transport in hybrid structures both in the normal and in the superconducting state.

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Probing the current-phase relation in Josephson point-contact junctions between $$\hbox {Pb}_{0.6}$$In$$_{0.4}$$ and $$\hbox {Ba}_{0.6}$$K$$_{0.4}$$(FeAs)$$_2$$ superconductors

Степанов

Lin

Gonnelli

et al. 2021

Sci Rep

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The Josephson effect in point contacts between an “ordinary” superconductor $$\hbox {Pb}_{0.6}$$ Pb 0.6 In$$_{0.4}$$ 0.4 ($$T_c \approx 6.6 \, {\mathrm {K}}$$ T c ≈ 6.6 K ) and single crystals of the Fe-based superconductor Ba$$_{0.6}$$ 0.6 K$$_{0.4}$$ 0.4 (FeAs)$$_2$$ 2 ($$T_c \approx 38.5 \, {\mathrm {K}}$$ T c ≈ 38.5 K ), was investigated. In order to shed light on the order parameter symmetry of Ba$$_{0.6}$$ 0.6 K$$_{0.4}$$ 0.4 (FeAs)$$_2$$ 2 , the dependence of the Josephson supercurrent $$I_s$$ I s on the temperature and on $$\sin (d\varphi )$$ sin ( d φ ) with $$d = 1, 2$$ d = 1 , 2 was studied. The dependencies of the critical current on temperature $$I_c (T)$$ I c ( T ) and of the amplitudes of the first current steps of the current–voltage characteristic $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) $$(n = 0, 1, 2)$$ ( n = 0 , 1 , 2 ) on the power of microwave radiation with frequency $$f = (1.5 \div 8)\, {\mathrm {GHz}}$$ f = ( 1.5 ÷ 8 ) GHz were measured. It is shown that the dependencies $$I_c (T)$$ I c ( T ) are close to the well-known Ambegaokar–Baratoff (AB) dependence for tunnel contacts between “ordinary” superconductors and to the dependence calculated by Burmistrova et al. (Phys Rev B 91, 214501 (2015)) for microshorts between an “ordinary” superconductor and a two-band superconductor with $$s \pm$$ s ± order parameter symmetry at certain values of the transparency of boundaries and thickness of the transition layer. It is found that the dependencies $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) cannot be approximated within the resistively shunted model using the normalized microwave frequencies $$\Omega = 2 \pi f / (2eV_c / \hbar )$$ Ω = 2 π f / ( 2 e V c / ħ ) with characteristic voltages $$V_c = I_c R_N$$ V c = I c R N , $$(R_N$$ ( R N —normal resistance of the contact) found from the low-voltage parts of the current–voltage characteristics. The reasons for this failure are discussed and a method is proposed for accurately determining the value of $$\Omega$$ Ω , which takes into account all the features of the point contact affecting the period of the dependence $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) . An analysis of the $$I_c (T)$$ I c ( T ) and $$i_n^{exp} (\sqrt{P})$$ i n exp ( P ) dependencies shows that the superconducting current of the Josephson contacts under investigation is proportional to the $$\sin$$ sin of the phase difference $$\varphi$$ φ , $$I_s = I_c sin(\varphi )$$ I s = I c s i n ( φ ) . The implications of these results on the symmetry of the order parameter are also discussed.

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Theory of Tunneling Spectroscopy of Multi-Band Superconductors

Cited by 27 publications

References 88 publications

Josephson current in Fe-based superconducting junctions: Theory and experiment

Josephson current in Fe-based superconducting junctions: Theory and experiment

Electronic transport through ferromagnetic and superconducting junctions with spin-filter tunneling barriers

Probing the current-phase relation in Josephson point-contact junctions between $$\hbox {Pb}_{0.6}$$In$$_{0.4}$$ and $$\hbox {Ba}_{0.6}$$K$$_{0.4}$$(FeAs)$$_2$$ superconductors

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