Andreev bound states in topological superconductors
Yukio Tanaka1, Lu Bo1,, K. Yada1, A. Yamakage1, M. Sato2
1Department of Applied Physics, Nagoya University
2Yukawa Institute, Kyoto University
e-mail: ytanaka@nuap.nagoya-u.ac.jp
It is known that Andreev bound state is an important ingredient to identify unconventional superconductors [1]. Up to now, there have been several types of Andreev bound states stemming from their topological origins [2-3]. It can be classified into i)dispersionless flat band type realized in cuprate, ii)linear dispersion type realized in chiral superconductor like Sr2RuO4, iii)helical dispersion type realized in non-centrosymmetric superconductor and iv)cone type in the surface state on B-phase of superfluid 3He [3].
It has been noted that certain surfaces of Weyl semimetals have bound states forming open Fermi arcs, which are never seen in typical metallic states. We show that the Fermi arcs enable them to support an even more exotic surface state with crossed flat bands in the superconducting state. We clarify the topological origin of the crossed dispersionless flat bands and the relevant symmetry that stabilizes the cross point. Our symmetry analysis are applicable to known candidate materials of time-reversal breaking Weyl semimetals[4].
[1]S. Kashiwaya and Y. Tanaka, Rep. Prog. Phys. 63 1641 (2000).
[2]Y. Tanaka, M. Sato, and N. Nagaosa, J. Phys. Soc. Jpn. 81 011013 (2012).
[3] M. Sato, et al., Phys. Rev. Lett. 103 (2009) 020401.
[4] B. Lu, K. Yada, M. Sato, and Y. Tanaka, Phys. Rev. Lett. 114 09
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