# Berlin 2015 – wissenschaftliches Programm

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# TT: Fachverband Tiefe Temperaturen

## TT 109: Transport: Majorana Fermions (jointly with DS, HL, MA, O)

### TT 109.6: Vortrag

### Freitag, 20. März 2015, 11:00–11:15, H 0104

**Thermal conductance as a probe of the non-local order parameter for a topological superconductor with gauge fluctuations** — •Fabian Hassler^{1}, Bernard van Heck^{2}, Emilio Cobanera^{3}, and Jascha Ulrch^{1} — ^{1}JARA Institute for Quantum Information, RWTH Aachen University, 52056 Aachen, Germany — ^{2}Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherlands — ^{3}Institute for Theoretical Physics, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands

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 *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 non-local order parameters for emergent or simulated topological quantum order.