Transport signatures of quasiparticle poisoning in a Majorana island

TL;DR

This study examines quasiparticle poisoning effects in a Majorana island, revealing shadow Coulomb diamonds, estimating parity lifetimes, and analyzing Majorana hybridization through transport measurements.

Contribution

It provides the first detailed analysis of quasiparticle poisoning signatures and parity lifetime estimates in strongly coupled Majorana islands.

Findings

Shadow Coulomb diamonds indicate excited poisoned states.

Estimated parity lifetime is approximately 1 microsecond.

Fluctuations in Coulomb peak spacing are consistent with Majorana hybridization.

Abstract

We investigate effects of quasiparticle poisoning in a Majorana island with strong tunnel coupling to normal-metal leads. In addition to the main Coulomb blockade diamonds, "shadow" diamonds appear, shifted by 1e in gate voltage, consistent with transport through an excited (poisoned) state of the island. Comparison to a simple model yields an estimate of parity lifetime for the strongly coupled island (~ 1 {\mu}s) and sets a bound for a weakly coupled island (> 10 {\mu}s). Fluctuations in the gate-voltage spacing of Coulomb peaks at high field, reflecting Majorana hybridization, are enhanced by the reduced lever arm at strong coupling. In energy units, fluctuations are consistent with previous measurements.