Speaker
Description
The topological superconductivity with Majorona zero modes (MZM) is of
fundamental scientific importance, due to their proposed application in the
braiding-based quantum computing [1]. The first theoretical proposal for
the realization of the MZM was involved placing an one dimensional (1D)
quantum wire with spinless electrons on a p-wave superconductors [2].
However, from the material science point of view this conceptually simple
model is hard to realize as spinless electron does not exist in nature, and
p-wave superconductors are, at best, rare. Later several proposals were put
forward to eliminate these difficulties by ingeniously combining the
proximity induced s-wave superconductivity, the Rashba spin-orbit coupling
(RSOC), and the broken time reversal (TR) symmetry [3]. The RSOC is needed
for the spin-momentum locking [4]. TR symmetry breaking is needed to
create, in effect, the spinless electrons. Using aforementioned ideas,
broadly three types of platforms have been engineered by placing [5]: (i)
topological insulators on superconductor [6, 7], (ii) semiconductor with
strong spin-orbit coupling on superconductor [8], or (iii) chain of
magnetic atoms on superconductor[9, 10]. Despite these experimental
successes, several concerns remain; mainly the requirements of the strong
RSOC and the external magnetic field. The former limits the candidate
materials which can be placed over the superconductor; the later limits the
possible superconducting substrate. Moreover the crystal symmetry
consideration greatly shrink the possible superconductors supporting
topological characters [11]. The external magnetic field is the principal
hindrance, as most of the experiments use s-wave superconductors in which
strong enough magnetic field will destroy the superconductivity. Hence,
naturally the question arises, can we get rid of the constraint possessed
by the magnetic field? It is the goal of this work to suggest a different
route to realizing MZM without magnetic field and RSOC.
We show that the 1D topological superconductivity can be placed in the
context of phenomena associated with strongly correlated electron systems. Here we propose a system consisting of a one-dimensional chain of strongly correlated fermions placed on a superconducting (SC) substrate that exhibits a spin-singlet extended s-wave pairing. Strong electron correlation is shown to transform an extended s-wave SC into a topological SC. In contrast to the approaches based on the mean-field treatment, no Zeeman or exchange magnetic field is needed to produce such an effect.
[1] S. D. Sarma, M. Freedman, and C. Nayak, npj Quantum Information 1, 1
(2015).
[2] A. Y. Kitaev, Physics-Uspekhi 44, 131 (2001).
[3] J. Alicea, Reports on Progress in Physics 75, 076501 (2012).
[4] A. Manchon, H. C. Koo, J. Nitta, S. M. Frolov, and R. A. Duine, Nature
Materials 14, 871 (2015).
[5] K. Flensberg, F. Von Oppen, and A. Stern, Nature Reviews Materials 6,
944 (2021).
[6] M. Z. Hasan and C. L. Kane, Reviews of Modern Physics 82, 3045 (2010).
[7] X.-L. Qi and S.-C. Zhang, Reviews of Modern Physics 83, 1057 (2011).
[8] R. M. Lutchyn, E. P. A. M. Bakkers, L. P. Kouwenhoven, P. Krogstrup, C. M. Marcus, and Y. Oreg, Nature Reviews Materials 3, 52 (2018).
[9] S. Nadj-Perge, I. K. Drozdov, B. A. Bernevig, and A. Yazdani, Physical
Review B 88, 020407 (2013).
[10] S. Nadj-Perge, I. K. Drozdov, J. Li, H. Chen, S. Jeon, J. Seo, A. H.
MacDonald, B. A. Bernevig, and A. Yazdani, Science 346, 602 (2014).
[11] S. Ono, H. C. Po, and H. Watanabe, Science Advances 6, eaaz8367 (2020).
