Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te)
Source abstract
Abstract
Majorana quasiparticles in condensed matter are important for topological quantum computing1-3, but remain elusive. Vortex cores of topological superconductors may accommodate Majorana quasiparticles that appear as the Majorana bound state (MBS) at zero energy4,5. The iron-based superconductor Fe(Se,Te) possesses a superconducting topological surface state6-9 that was investigated by scanning tunnelling microscopy (STM) studies, which suggest such a zero-energy vortex bound state (ZVBS)10,11. Here we present ultrahigh energy-resolution spectroscopic imaging (SI)-STM to clarify the nature of the vortex bound states in Fe(Se,Te). We found the ZVBS at 0 ± 20 μeV, which constrained its MBS origin, and showed that some vortices host the ZVBS but others do not. We show that the fraction of vortices hosting the ZVBS decreases with increasing magnetic field and that local quenched disorders are not related to the ZVBS. Our observations elucidate the necessary conditions to realize the ZVBS, which paves the way towards controllable Majorana quasiparticles.
Source: europepmc · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Topological Materials and Phenomena · Iron-based superconductors research · Rare-earth and actinide compounds
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (32)
Show source-provided references
1. Nayak, C., Simon, S. H., Stern, A., Freedman, M. & Das Sarma, S. Non-Abelian anyons and topological quantum computation. Rev. Mod. Phys. 80, 1083–1159 (2008).10.1103/RevModPhys.80.1083 ↗
2. Alicea, J. New directions in the pursuit of Majorana fermions in solid state systems. Rep. Prog. Phys. 75, 076501 (2012).10.1088/0034-4885/75/7/076501 ↗
3. Sato, M. & Ando, Y. Topological superconductors: a review. Rep. Prog. Phys. 80, 076501 (2017).10.1088/1361-6633/aa6ac7 ↗
4. Ivanov, D. A. Non-Abelian statistics of half-quantum vortices in p-wave superconductors. Phys. Rev. Lett. 86, 268–271 (2001).10.1103/PhysRevLett.86.268 ↗
5. Fu, L. & Kane, C. L. Superconducting proximity effect and Majorana fermions at the surface of a topological insulator. Phys. Rev. Lett. 100, 096407 (2008).10.1103/PhysRevLett.100.096407 ↗
6. Wang, Z. et al. Topological nature of the FeSe0.5Te0.5 superconductor. Phys. Rev. B 92, 115119 (2015).10.1103/PhysRevB.92.115119 ↗
7. Wu, X. et al. Topological characters in Fe(Te1−xSex) thin films. Phys. Rev. B 93, 115129 (2016).10.1103/PhysRevB.93.115129 ↗
8. Xu, G. et al. Topological superconductivity on the surface of Fe-based superconductors. Phys. Rev. Lett. 117, 047001 (2016).10.1103/PhysRevLett.117.047001 ↗
9. Zhang, P. et al. Observation of topological superconductivity on the surface of an iron-based superconductor. Science 360, 182–186 (2018).10.1126/science.aan4596 ↗
10. Wang, D. et al. Evidence for Majorana bound states in an iron-based superconductor. Science 362, 333–335 (2018).10.1126/science.aao1797 ↗
11. Chen, M. et al. Discrete energy levels of Caroli–de Gennes–Matricon states in quantum limit in FeTe0.55Se0.45. Nat. Commun. 9, 970 (2018).10.1038/s41467-018-03404-8 ↗
12. Mourik, V. et al. Signatures of Majorana fermions in hybrid superconductor–semiconductor nanowire devices. Science 336, 1003–1007 (2012).10.1126/science.1222360 ↗
13. Nadj-Perge, S. et al. Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor. Science 346, 602–607 (2014).10.1126/science.1259327 ↗
14. Kim, H. et al. Toward tailoring Majorana bound states in artificially constructed magnetic atom chains on elemental superconductors. Sci. Adv. 4, eaar5251 (2018).10.1126/sciadv.aar5251 ↗
15. Hosur, P., Ghaemi, P., Mong, R. S. K. & Vishwanath, A. Majorana modes at the ends of superconductor vortices in doped topological insulators. Phys. Rev. Lett. 107, 097001 (2011).10.1103/PhysRevLett.107.097001 ↗
16. Guan, S.-Y. et al. Superconducting topological surface states in the noncentrosymmetric bulk superconductor PbTaSe2. Sci. Adv. 2, e1600894 (2016).10.1126/sciadv.1600894 ↗
17. Iwaya, K. et al. Full-gap superconductivity in spin-polarised surface states of topological semimetal β-PdBi2. Nat. Commun. 8, 976 (2017).10.1038/s41467-017-01209-9 ↗
18. Hanaguri, T., Niitaka, S., Kuroki, K. & Takagi, H. Unconventional s-wave superconductivity in Fe(Se,Te). Science 328, 474–476 (2010).10.1126/science.1187399 ↗
19. Rinott, S. et al. Tuning across the BCS–BEC crossover in the multiband superconductor Fe1+ySexTe1−x: an angle-resolved photoemission study. Sci. Adv. 3, e1602372 (2017).10.1126/sciadv.1602372 ↗
20. Caroli, C., de Gennes, P. G. & Matricon, J. Bound fermion states on a vortex line in a type II superconductor. Phys. Lett. 9, 307–309 (1964).10.1016/0031-9163(64)90375-0 ↗
21. Xu, J.-P. et al. Experimental detection of a Majorana mode in the core of a magnetic vortex inside a topological insulator-superconductor Bi2Te3/NbSe2 heterostructure. Phys. Rev. Lett. 114, 017001 (2015).10.1103/PhysRevLett.114.017001 ↗
22. Sun, H.-H. et al. Majorana zero mode detected with spin selective Andreev reflection in the vortex of a topological superconductor. Phys. Rev. Lett. 116, 257003 (2016).10.1103/PhysRevLett.116.257003 ↗
23. Machida, T., Kohsaka, Y. & Hanaguri, T. A scanning tunneling microscope for spectroscopic imaging below 90 mK in magnetic fields up to 17.5 T. Rev. Sci. Instrum. 89, 093707 (2018).10.1063/1.5049619 ↗
24. Yin, J.-X. et al. Observation of a robust zero-energy bound state in iron-based superconductor Fe(Te,Se). Nat. Phys. 11, 543–546 (2015).10.1038/nphys3371 ↗
25. Massee, F. et al. Imaging atomic-scale effects of high-energy ion irradiation on superconductivity and vortex pinning in Fe(Se,Te). Sci. Adv. 1, e1500033 (2015).10.1126/sciadv.1500033 ↗
26. Liu, Q. et al. Robust and clean Majorana zero mode in the vortex core of high-temperature superconductor (Li0.84Fe0.16)OHFeSe. Phys. Rev. X 8, 041056 (2018).
27. Hayashi, N., Isoshima, T., Ichioka, M. & Machida, K. Low-lying quasiparticle excitations around a vortex core in quantum limit. Phys. Rev. Lett. 80, 2921–2924 (1998).10.1103/PhysRevLett.80.2921 ↗
28. Biswas, R. R. Majorana fermions in vortex lattices. Phys. Rev. Lett. 111, 136401 (2013).10.1103/PhysRevLett.111.136401 ↗
29. Chiu, C.-K., Machida T., Huang Y., Hanaguri T. & Zhang F.-C. Scalable Majorana vortex modes in iron-based superconductors. Preprint at https://arxiv.org/abs/1904.13374 (2019).10.1126/sciadv.aay0443 ↗
30. Liu, T. & Franz, M. Electronic structure of topological superconductors in the presence of a vortex lattice. Phys. Rev. B 92, 134519 (2015).10.1103/PhysRevB.92.134519 ↗
31. Sun, Y. et al. Effects of annealing, acid and alcoholic beverages on Fe1+yTe0.6Se0.4. Supercond. Sci. Technol. 26, 015015 (2013).10.1088/0953-2048/26/1/015015 ↗
32. Sun, Y. et al. Dynamics and mechanism of oxygen annealing in Fe1+yTe0.6Se0.4 single crystal. Sci. Rep. 4, 4585 (2014).10.1038/srep04585 ↗