Zero--energy Majorana modes in condensed matter physics
dr inż. Anna Gorczyca-Gora, Zakład Fizyki Teoretycznej, Instytut Fizyki UŚ,
05.04.2019, 12:00 w sali A/1/04
Quasiparticles induced at the edges of spinless ($p$-wave)
superconducting sample in one or two dimensions have the exotic
character of zero-energy bound states. These emergent Majorana-type
objects have been predicted in various systems, such as topological
insulators, semiconducting nanowires, ferromagnetic chains coupled to
$s$-wave superconducting reservoirs. The most convincing experimental
evidence for the zero-energy Majorana modes has been provided so far by
the tunneling measurement using the nanoscopic chains proximity coupled
to the $s$-wave superconducting reservoir.
In my talk I will discuss the properties of the inhomogeneous Rashba
chain coupled to a superconducting substrate, hosting the Majorana
quasiparticles near its edges. Despite common belief that the Majorana
quasiparticles are robust to environmental influence, our results
indicate that this is not truly the case and reveal that sufficiently
strong disorder would be detrimental for the Majorana quasiparticles,
causing a transition from the topologically nontrivial to trivial
superconducting phases. On the other hand, single quantum impurities
have also very unusual interplay with the Majorana quasiparticle states.
Under specific conditions they can effectively induce additional pairs
of the Majorana states.
Yet, the Rashba chain model has its limitations important for
experimental realization. That is why we propose another model of
experimental relevance, namely a chain of the localized magnetic
impurities whose moments are coupled to the spins of itinerant
electrons, deposited on a surface of $s$--wave bulk superconductor.
With use of Monte Carlo simulations we have checked thermal stability of
Majorana modes and estimated $T_c$.This evaluation should also be taken
into account when considering future applications of the Majorana
quasiparticles for quantum computing.