Competing Vortex Topologies in Iron-based Superconductors

Hu, Lun-Hui; Wu, Xianxin; Liu, Chaoxing; Zhang, Rui-Xing

doi:10.48550/arxiv.2110.11357

Cited by 3 publications

(3 citation statements)

References 85 publications

(117 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As is discussed in reference [69], the symmetry protected Majorana Krammers pairs in a topological superconductor should satisfy the condition that its superconducting gap is odd under certain symmetry operation. Here the four zero energy vortex bound states in the s-wave SC-NLSM system can be stabilized by the mirror symmetry, which is similar to the double Majorana vortex bound states being studied in references [70,71]. Note that, the mirror operator has two eigenvalues, as a result, two pairs of Majorana vortex bound states can survive.…”

Section: Vortex Bound States Of the Spinful Sc-nlsm Systemsupporting

confidence: 51%

Fragile topology in nodal-line semimetal superconductors

Wang

Zhou

2022

New J. Phys.

View full text Add to dashboard Cite

Fragile topological insulator are an exotic phase with unstable edge states. Its nontrivial band topology can be removed by coupling to additional topologically trivial bands. Here we reveal that the fragile band topology can be realized in the inversion symmetric odd parity superconducting nodal line semimetal (SC-NLSM) materials with and without the spin orbital coupling. Without the spin orbital coupling, both the $s$-wave SC-NLSM and the $p$-wave SC-NLSM host a pair of Majorana zero modes on the system surface. For the spinful case, it has fourfold inverted bands and generates fourfold degenerate Majorana surface/edge states. However, we verify that for all of the systems we considered, they belong to the fragile topological superconducting system based on the Wilson loop method. The vortex bound states are studied numerically. Whether the stable Majorana zero modes exist depend strongly on the systems.

show abstract

Section: Vortex Bound States Of the Spinful Sc-nlsm Systemsupporting

confidence: 51%

Fragile topology in nodal-line semimetal superconductors

Wang

Zhou

2022

New J. Phys.

View full text Add to dashboard Cite

show abstract

“…Remarkably, such a topological requirement can be further relaxed for vortex-trapped MZMs if the bulk electronic band structure, instead of the superconductivity itself, carries a non-trivial topological index [10,11]. This spirit also inspires another intensive search of topological band materials with intrinsic yet non-topological SC [12][13][14][15][16][17], with many promising candidates discovered [18][19][20][21][22][23][24][25]. However, as far as we know, the possibility of trapping MZMs in trivial SCs with trivial electronic band structures has not been carefully studied in the literature.…”

Section: Introductionmentioning

confidence: 99%

Topological Superconducting Vortex From Trivial Electronic Bands

Hu¹,

Zhang²

2022

Preprint

Self Cite

View full text Add to dashboard Cite

Superconducting vortices are promising traps to confine non-Abelian Majorana quasi-particles. It has been widely believed that bulk-state topology, of either normal-state or Cooper-paired electron wavefunctions, is crucial for enabling Majorana zero modes. This common belief has shaped two major search directions for Majorana modes, in either intrinsic topological superconductors or trivial superconductors with topological electronic band structures. Here we show that Majoranacarrying vortex is not a privilege of bulk-state topology, but can arise from superconducting trivial bands as well. Notably, even for superconductors with topological band structures, the existence of ubiquitous low-energy trivial bands can significantly change the conclusion of vortex Majorana physics that is based on simplified topological-band-only models. We predict that the trivial bands in superconducting HgTe-class materials are responsible for inducing anomalous vortex topology that goes beyond any existing theoretical paradigms. A feasible scheme of strain-controlled Majorana engineering and a new experimental "smoking gun" are also discussed. Our work provides new guidelines for Majorana search in general superconductors.

show abstract

“…Second and unique to LiFeAs, there is a set of bulk Dirac fermion states sitting ~ 10 meV above the Fermi level, which is characteristic of a topological Dirac semimetal. This dual topological nature complicates the vortex core spectrum for the unstrained LiFeAs, which appeared gapless, and prohibited the identification of the discrete vortex core states 6,10,41,42 . To uncover the electronic structure of the strained LiFeAs, we take wide energy scale dI/dV spectra in the unstrained (lower region in Extended Data Fig.…”

mentioning

confidence: 99%

Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs

Cao

et al. 2022

Nature

View full text Add to dashboard Cite

Majorana zero modes (MZMs) obey non-Abelian statistics and are considered building blocks for constructing topological qubits 1,2 . Iron-based superconductors with topological band structures have emerged as promising hosting materials, since isolated candidate MZMs in the quantum limit have been observed inside the topological vortex cores 3-9 . However, these materials suffer from issues related to alloying-induced disorder, uncontrolled vortex lattices 10-13 and a low yield of topological vortices 5-8 . Here, we report the formation of an ordered and tunable MZM lattice in naturally-strained stoichiometric LiFeAs by scanning tunneling microscopy/spectroscopy (STM/S). We observe biaxial charge density wave (CDW) stripes along the Fe-Fe and As-As directions in the strained regions. The vortices are pinned on the CDW stripes in the As-As direction and form an ordered lattice. We detect more than 90 percent of the vortices to be topological and possess the characteristics of isolated MZMs at the vortex center, forming an ordered MZM lattice with the density and the geometry tunable by an external magnetic field. Remarkably, with decreasing the spacing of neighboring vortices, the MZMs start to couple with each other. Our findings provide a new pathway towards tunable and ordered MZM lattices as a platform for future topological quantum computation.The long quest for Majorana excitations [14][15][16][17][18][19] has been fueled by recent experimental progress in material platforms where the localized MZM has been observed 16,[20][21][22][23] . Among these platforms, ironbased superconductors are considered promising for the observation of clean and robust MZMs 3-5 . FeTe0.55Se0.45 was the first iron-based superconductor found to possess topological surface states (TSS) 24,25 . The largeratio, where Δ is the superconducting (SC) energy gap and 𝐸 𝐹 is the Fermi energy, allows the observation of an isolated MZM in the center of a topological vortex 4 , which exhibits nearly quantized plateaus in differential conductance 9 . Later on, stoichiometric iron pnictides were investigated and the existence of MZMs has been verified in CaKFe4As4 (ref. 8 ) and LiFeAs (ref. 6 ). Very recently, 1D dispersing Majorana modes and MZMs have been observed in the layered 2D superconductors with topological band structures [26][27][28] . However, these platforms suffer from alloyinginduced disorder, uncontrolled vortex lattice and a low yield of topological vortices, hindering their potential applications.We start with LiFeAs crystal due to its homogeneous bulk electronic structure, well-defined cleaving surface and rich topological band structures 29 . LiFeAs belongs to the tetragonal crystal system, with lattice constants a=b=3.8 Å and c=6.3 Å (Fig. 1a). The As-As atomic direction defines the high-

show abstract

Competing Vortex Topologies in Iron-based Superconductors

Cited by 3 publications

References 85 publications

Fragile topology in nodal-line semimetal superconductors

Fragile topology in nodal-line semimetal superconductors

Topological Superconducting Vortex From Trivial Electronic Bands

Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs

Contact Info

Product

Resources

About