ELFT HÍRADÓ

[Janos Asboth <asboth AT phy.bme.hu>]

Meghívó

BME Elméleti Fizika Szeminárium,

február 21. péntek 10h15,

1111 Budapest, Budafoki út 8., BME F III. magasföldszint 01.,
Elméleti Fizika Tanszék szemináriumi szoba

Eduardo Lee (Univ. Autonoma de Madrid, Dept of Cond. Mat. Phys):

Andreev bound states in hybrid superconductor-semiconductor nanowire
devices

We perform tunneling measurements to study the low-energy states of quantum
dots formed in semiconductor nanowires and coupled strongly to a
superconductor. Although non-topological in nature, these states, commonly
known as Andreev bound states (ABSs) or Yu-Shiba-Rusinov states, hold
relevance in the context of topological superconductivity. Indeed, ABSs are
expected to evolve towards Majorana modes across a topological phase
transition when in the long wire limit. In addition, understanding the ABS
spectra of hybrid nanowire devices is important for the interpretation of
experiments directed at the observation of Majorana modes. In this work, we
perform a detailed study of the sub-gap states of a tunable spin-½ quantum
dot. We first exploit the ability to control the coupling between the dot
and the superconductor to explore the phase diagram of the possible ground
states of the system: a spin singlet or a magnetic doublet. By applying
external magnetic fields, we study the spin texture of the Andreev states
and demonstrate zero-bias crossings resulting from parity-changing phase
transitions.  Finally, we evaluate the impact of mesoscopic tunnel probes
in the detection of ABSs. We show that the non-trivial density of states of
such probes yields numerous replicas of the sub-gap states, thereby leading
to crowded Andreev spectra.

Minden érdeklődőt szeretettel várunk.

Asbóth János
szemináriumi koordinátor