TY - BOOK

T1 - Quasiparticle Dynamics and Exponential Protection in Majorana Islands

AU - Albrecht, Sven Marian

PY - 2016

Y1 - 2016

N2 - This thesis presents measurements on Majorana islands:semiconductor-superconductor hybrid nanowire quantum dotsin the trivial and the topological superconducting phase.We fabricate Majorana island devices based on indium arsenidenanowires with an epitaxially matched aluminum half-shell. Measuringquasiparticle transport, we observe a gate voltage dependenteven-odd Coulomb blockade pattern, associated with quasiparticleoccupation of bound states, for which we demonstrate state paritylifetimes exceeding 10 milliseconds.Using Coulomb-blockade spectroscopy and varying the magneticfield, we measure oscillating energy splittings of near-zero energystates, consistent with theoretical predictions for hybridized Majoranamodes. We present a length study of Majorana islands anddemonstrate the exponential suppression of energy splitting with increasingisland length, as expected for Majorana modes, with a characteristiclength of 260 nm. For long devices exceeding one micron,transport at high magnetic fields shows discrete zero-energy states,with an energy gap to a higher-energy continuum, and evenly spacedCoulomb-blockade conductance peaks, a signature of teleportationvia Majorana modes. A preliminary analysis shows that Coulombpeaks also feature an alternating magnetic field dependent skew, thesubject of future work.We additionally observe novel transport signatures of quasiparticlepoisoning in a Majorana island strongly coupled to normal metalleads. Numerical simulations show good agreement with measurementsand allow us to extract a time for poisoning of the island’sground state from the leads of 3 microseconds.

AB - This thesis presents measurements on Majorana islands:semiconductor-superconductor hybrid nanowire quantum dotsin the trivial and the topological superconducting phase.We fabricate Majorana island devices based on indium arsenidenanowires with an epitaxially matched aluminum half-shell. Measuringquasiparticle transport, we observe a gate voltage dependenteven-odd Coulomb blockade pattern, associated with quasiparticleoccupation of bound states, for which we demonstrate state paritylifetimes exceeding 10 milliseconds.Using Coulomb-blockade spectroscopy and varying the magneticfield, we measure oscillating energy splittings of near-zero energystates, consistent with theoretical predictions for hybridized Majoranamodes. We present a length study of Majorana islands anddemonstrate the exponential suppression of energy splitting with increasingisland length, as expected for Majorana modes, with a characteristiclength of 260 nm. For long devices exceeding one micron,transport at high magnetic fields shows discrete zero-energy states,with an energy gap to a higher-energy continuum, and evenly spacedCoulomb-blockade conductance peaks, a signature of teleportationvia Majorana modes. A preliminary analysis shows that Coulombpeaks also feature an alternating magnetic field dependent skew, thesubject of future work.We additionally observe novel transport signatures of quasiparticlepoisoning in a Majorana island strongly coupled to normal metalleads. Numerical simulations show good agreement with measurementsand allow us to extract a time for poisoning of the island’sground state from the leads of 3 microseconds.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122654458205763

M3 - Ph.D. thesis

BT - Quasiparticle Dynamics and Exponential Protection in Majorana Islands

PB - The Niels Bohr Institute, Faculty of Science, University of Copenhagen

ER -