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Evidence for an anomalous current-phase relation in topological insulator Josephson junctions
C Kurter1, A D K Finck1, Y S Hor2
1Department of Physics and Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Nature Communications
|June 2, 2015
Summary
Josephson junctions with topological insulators show unusual electrical properties due to special quantum states. These findings suggest a potential pathway for novel superconducting devices and quantum computing applications.
Area of Science:
- Condensed Matter Physics
- Quantum Materials Science
- Superconductivity
Background:
- Topological insulators host unique electronic states at their boundaries.
- Josephson junctions with topological insulator weak links can exhibit non-sinusoidal current-phase relations.
- Zero-energy Majorana-bound states are predicted at a phase difference of π in such systems.
Purpose of the Study:
- To investigate the properties of Josephson junctions and superconducting quantum interference devices (SQUIDs) incorporating topological insulator weak links.
- To understand the nature of low-energy Andreev-bound states and their influence on device characteristics.
- To explore the potential role of Majorana-bound states in these systems.
Main Methods:
- Fabrication of Josephson junctions and SQUIDs with topological insulator weak links.
- Interferometry measurements to study the current-phase relation and device oscillations.
- Analysis of diffraction patterns and SQUID oscillations as a function of chemical potential and temperature.
Main Results:
- Nodes in single-junction diffraction patterns and SQUID oscillations are lifted and independent of chemical potential.
- At high temperatures, SQUID oscillations revert to conventional behavior, excluding asymmetry.
- Node-lifting is consistent with co-existing sinusoidal and non-sinusoidal current-phase relations from Andreev-bound states.
- Finite nodal currents suggest anomalous supercurrent contributions, possibly from Majorana-bound states or inhomogeneity.
Conclusions:
- The observed phenomena in topological insulator Josephson junctions are attributed to low-energy Andreev-bound states.
- The lifting of nodes and finite nodal currents provide evidence for non-conventional superconducting behavior.
- Further investigation is needed to definitively confirm the role of Majorana-bound states versus material inhomogeneity.
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