Odd-frequency pairing in the edge states of superconducting pnictides in the coexistence phase with antiferromagnetism

Youmans, Cody; Ghazaryan, Areg; Kargarian, Mehdi; Ghaemi, Pouyan

doi:10.1103/physrevb.98.144517

Cited by 8 publications

(3 citation statements)

References 72 publications

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“…In the phase of coexistence of superconductivity and a spin density wave, which is experimentally observed in pnictides, superconductivity with a spin-triplet order parameter that is even in orbital angular momentum (p-even, s-wave) and odd in frequency (T -odd) [268], can form at the boundary of the material due to the presence of magnetic ordering and translation symmetry breaking; this superconductivity can be accompanied by the formation of MMs [269][270][271].…”

Section: Introduction To the Problemmentioning

confidence: 99%

Topological superconductivity and Majorana states in low-dimensional systems

Val'kov,

Shustin,

Aksenov

et al. 2022

Preprint

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We discuss the properties of topologically nontrivial superconducting phases and the conditions for their realization in condensed matter, the criteria for the appearance of elementary Majorana-type excitations in solids, and the corresponding principles and experimental methods for identifying Majorana bound states (MBSs).Along with the well-known Kitaev chain and superconducting nanowire (SW) models with spin-orbit coupling in an external magnetic field, we discuss models of quasi-two-dimensional materials in which MBSs are realized in the presence of noncollinear spin ordering. For finite-length SWs, we demonstrate a cascade of quantum transitions occurring with a change in the magnetic field, accompanied by a change in the fermion parity of the ground state. The corresponding anomalous behavior resonances and the spatial structure of the lowest-energy SW state. The conditions for the occurrence of an MBS in the phase of the coexistence of chiral d + id superconductivity and 120-degree spin ordering are determined in the framework of the t − J − V model on a triangular lattice. We take electron-electron interactions into account in discussing the topological invariants of low-dimensional superconducting materials with noncollinear spin ordering. The formation of Majorana modes in regions with an odd value of a topological Z invariant is demonstrated. The spatial structure of these excitations in the Hubbard fermion ensemble is determined.

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Section: Introduction To the Problemmentioning

confidence: 99%

Topological superconductivity and Majorana states in low-dimensional systems

Val'kov,

Shustin,

Aksenov

et al. 2022

Preprint

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“…A very promising route in generating odd-frequency pair correlations is in multiband (multiorbital, multichannel) systems [13,14], where, under fairly general conditions, such as band hybridization, odd-frequency interband pairing is generated even if the superconducting order parameter is strictly intraband and even-frequency. Candidates where such conditions * kanasugi.shouta.62w@st.kyoto-u.ac.jp are met were conceived in iron-pnictide superconductors [15,16], systems with disorder [17], multi-channel Kondo systems [18,19], quantum spin Hall insulators on a honeycomb lattice [20], and driven systems [21]. In the presence of spin-orbit coupling, such as the case of Sr 2 RuO 4 , it leads to Kerr effect [22,23].…”

Section: Introductionmentioning

confidence: 99%

Ferroelectricity-induced multiorbital odd-frequency superconductivity in SrTiO$_3$

Kanasugi,

Kuzmanovski,

Balatsky

et al. 2020

Preprint

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We demonstrate that SrTiO3 can be a platform for observing the bulk odd-frequency superconducting state owing to the multiorbital/multiband nature. We consider a three-orbital tight-binding model for SrTiO3 in the vicinity of a ferroelectric critical point. Assuming an intraorbital spin-singlet s-wave superconducting order parameter, it is shown that the odd-frequency pair correlations are generated due to the intrinsic LS coupling which leads to the local orbital mixing. Furthermore, we show the existence of additional odd-frequency pair correlations in the ferroelectric phase, which is induced by an odd-parity orbital hybridization term proportional to the ferroelectric order parameter. We also perform a group theoretical classification of the odd-frequency pair amplitudes based on the fermionic and space group symmetries of the system. The classification table enables us to predict dominant components of the odd-frequency pair correlations based on the symmetry of the normal state Hamiltonian that we take into account. Furthermore, we show that experimental signatures of the odd-parity orbital hybridization, which is an essential ingredient for the ferroelectricity-induced odd-frequency pair correlations, can be observed in the spectral functions and density of states.

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“…Introduction: To date, one of the major impediments in the search for Majorana fermions (MFs) is that a requisite topological superconductivity, either intrinsic [1,2] or induced in a host material via a proximity coupling to a standard s-wave superconductor [3][4][5][6]. Of the available materials that possess topology, superconductivity and magnetism, iron-based superconductors are of recent interest [7][8][9][10][11][12][13][14][15]. In particular, the iron-based superconductor FeTe 0.55 Se 0.45 (FTS) has recently been shown to have strong spin-orbit interactions and band inversion that result in a helical, topologically-protected, Dirac cone on the surface [16][17][18][19].…”

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confidence: 99%

Effect of Zeeman coupling on the Majorana vortex modes in iron-based topological superconductors

et al. 2020

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In the superconducting regime of FeTe (1−x) Sex, there exist two types of vortices which are distinct by the presence or absence of zero energy states in their core. To understand their origin, we examine the interplay of Zeeman coupling and superconducting pairings in three-dimensional metals with band inversion. Weak Zeeman fields are found to suppress the intra-orbital spin-singlet pairing, known to localize the states at the ends of the vortices on the surface. On the other hand, an orbital-triplet pairing is shown to be stable against Zeeman interactions, but leads to delocalized zero-energy Majorana modes which extend through the vortex. In contrast, the finite-energy vortex modes remain localized at the vortex ends even when the pairing is of orbital-triplet form. Phenomenologically, this manifests as an observed disappearance of zero-bias peaks within the cores of topological vortices upon increase of the applied magnetic field. The presence of magnetic impurities in FeTe (1−x) Sex, which are attracted to the vortices, would lead to such Zeeman-induced delocalization of Majorana modes in a fraction of vortices that capture a large enough number of magnetic impurities. Our results provide an explanation to the dichotomy between topological and non-topological vortices recently observed in FeTe (1−x) Sex.Introduction: To date, one of the major impediments in the search for Majorana fermions (MFs) is that a requisite topological superconductivity, either intrinsic [1,2] or induced in a host material via a proximity coupling to a standard s-wave superconductor [3-6]. Of the available materials that possess topology, superconductivity and magnetism, iron-based superconductors are of recent interest [7][8][9][10][11][12][13][14][15]. In particular, the iron-based superconductor FeTe 0.55 Se 0.45 (FTS) has recently been shown to have strong spin-orbit interactions and band inversion that result in a helical, topologically-protected, Dirac cone on the surface [16][17][18][19]. The phenomenology of vortices, proliferated in the presence of magnetic fields, is also noteworthy in FTS [20][21][22][23]. The low charge density in the superconducting phase of this system is experimentally advantageous as it results in large Caroli-de Gennes-Matricon (CDM) vortex mode gaps [24] which facilitates the spectral detection of zero-energy vortex modes via scanning tunneling microscopy (STM). Intriguingly, vortices in FTS show two distinct types of behavior: topological, carrying zero energy states consistent with the presence of MF, and trivial vortices that lack the zero energy state but carry finite energy CDMs.

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Odd-frequency pairing in the edge states of superconducting pnictides in the coexistence phase with antiferromagnetism

Cited by 8 publications

References 72 publications

Topological superconductivity and Majorana states in low-dimensional systems

Topological superconductivity and Majorana states in low-dimensional systems

Ferroelectricity-induced multiorbital odd-frequency superconductivity in SrTiO$_3$

Effect of Zeeman coupling on the Majorana vortex modes in iron-based topological superconductors

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