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Signatures of Jackiw-Rebbi resonance in the thermal conductance of topological Josephson junctions with magnetic islands

Josephson junctions in two-dimensional topological insulators with embedded magnetic domains can host a number of topological phases, in particular, Jackiw-Rebbi solitons and Majorana zero modes. These different non-trivial phases appear in such junctions for multiple-domain magnetic islands, showing a rich multi-gap structure. Features related to the interplay between superconductivity and magnetism in these systems cannot be easily discerned looking at behavior of the Andreev spectrum and the concomitant dc Josephson effect. Instead, the thermal conductance is very sensitive to the nature of the junction and the domain structure of the magnetic island. We present a detailed analysis of these properties in the case of a topological Josephson junction with a single and two-domain magnetic island. Configurations hosting soliton magnetic modes lead to a peculiar behavior of the thermal conductance relative to the thermal quantum, characterized by a negative slope as a function of the temperature, just above the superconducting critical temperature. At low temperatures, these junctions also show characteristic coherence patters in the behavior of the thermal conductance as function of the Josephson phase bias and the angle between the magnetizations of the domains.