We investigate the effect of quantum phase slips on a helical quantum wire coupled to a superconductor by proximity. The effective low-energy description of the wire is that of a Majorana chain minimally coupled to a dynamical Z 2 gauge field. Hence the wire emulates a matter-coupled gauge theory, with fermion parity playing the role of the gauged global symmetry. Quantum phase slips lift the ground-state degeneracy associated with unpaired Majorana edge modes at the ends of the chain, a change that can be understood as a transition between the confined and the Higgs-mechanism regimes of the gauge theory. We identify the quantization of thermal conductance at the transition as a robust experimental feature separating the two regimes. We explain this result by establishing a relation between thermal conductance and the Fredenhagen-Marcu string order parameter for confinement in gauge theories. Our work indicates that thermal transport could serve as a measure of nonlocal order parameters for emergent or simulated topological quantum order.

Thermal conductance as a probe of the nonlocal order parameter for a topological superconductor with gauge fluctuations / van Heck, B.; Cobanera, E.; Ulrich, J.; Hassler, and F.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 89:16(2014). [10.1103/PhysRevB.89.165416]

Thermal conductance as a probe of the nonlocal order parameter for a topological superconductor with gauge fluctuations

B. van Heck
Primo
;
2014

Abstract

We investigate the effect of quantum phase slips on a helical quantum wire coupled to a superconductor by proximity. The effective low-energy description of the wire is that of a Majorana chain minimally coupled to a dynamical Z 2 gauge field. Hence the wire emulates a matter-coupled gauge theory, with fermion parity playing the role of the gauged global symmetry. Quantum phase slips lift the ground-state degeneracy associated with unpaired Majorana edge modes at the ends of the chain, a change that can be understood as a transition between the confined and the Higgs-mechanism regimes of the gauge theory. We identify the quantization of thermal conductance at the transition as a robust experimental feature separating the two regimes. We explain this result by establishing a relation between thermal conductance and the Fredenhagen-Marcu string order parameter for confinement in gauge theories. Our work indicates that thermal transport could serve as a measure of nonlocal order parameters for emergent or simulated topological quantum order.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1655984
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