Möller, Gunnar, Cooper, N R, Gurarie, V (2011) Structure and consequences of vortexcore states in pwave superfluids. Physical Review B: Condensed Matter and Materials Physics, 83 . 014513. ISSN 01631829. (doi:10.1103/PhysRevB.83.014513) (KAR id:55590)
PDF
Author's Accepted Manuscript
Language: English
This work is licensed under a Creative Commons AttributionNonCommercialShareAlike 4.0 International License.


Download this file (PDF/1MB) 
Preview 
Request a format suitable for use with assistive technology e.g. a screenreader  
Official URL: http://dx.doi.org/10.1103/PhysRevB.83.014513 
Abstract
It is now well established that in twodimensional chiral $p$wave paired superfluids, the vortices carry zeroenergy
modes which obey nonabelian exchange statistics and can potentially be used for topological quantum computation.
In such superfluids there may also exist other excitations below the bulk gap inside the cores of vortices.
We study the properties of these subgap states, and argue that their
presence affects the topological protection of the zero modes.
In conventional superconductors where the chemical potential is of the order of the Fermi energy
of a noninteracting Fermi gas, there is a large number of subgap states and the minigap
towards the lowest of these states is a small fraction of the Fermi energy. It is therefore difficult
to cool the system to below the minigap and at experimentally available temperatures, transitions
between the subgap states, including the zero modes, will occur and can alter the quantum
states of the zeromodes. Consequently, qubits defined uniquely in terms of the zeromodes
do not remain coherent.
We show that compound qubits involving the zeromodes and the parity of the occupation number
of the subgap states on each vortex are still well defined. However, practical schemes taking into
account all subgap states would nonetheless be difficult to achieve.
We propose to avoid this difficulty by working in the regime of small chemical potential $\mu$, near the transition
to a strongly paired phase, where the number of subgap states is reduced. We develop the theory to describe
this regime of strong pairing interactions and we show how the subgap states are ultimately absorbed into the bulk gap.
Since the bulk gap also vanishes as $\mu\to 0$ there is an optimum value $\mu_c$ which maximises the combined gap.
We propose cold atomic gases as candidate systems where the regime of strong interactions can be explored,
and explicitly evaluate $\mu_c$ in a Feshbach resonant $^{40}$K gas.
Item Type:  Article 

DOI/Identification number:  10.1103/PhysRevB.83.014513 
Uncontrolled keywords:  Physics of Quantum Materials, superfluid, BECBCS crossover, pwave, superconductor, vortices, subgap state, Majorana, topological quantum computation, Physics of Quantum Materials 
Subjects: 
Q Science > QC Physics > QC173.45 Condensed Matter Q Science > QC Physics > QC174.12 Quantum theory 
Divisions:  Divisions > Division of Natural Sciences > Physics and Astronomy 
Depositing User:  Gunnar Moeller 
Date Deposited:  29 Sep 2016 14:49 UTC 
Last Modified:  16 Nov 2021 10:23 UTC 
Resource URI:  https://kar.kent.ac.uk/id/eprint/55590 (The current URI for this page, for reference purposes) 
 Link to SensusAccess
 Export to:
 RefWorks
 EPrints3 XML
 BibTeX
 CSV
 Depositors only (login required):