Multiterminal transport spectroscopy of subgap states in Coulomb-blockaded superconductors

Abstract

Subgap states are responsible for the low-bias transport features of hybrid superconducting--semiconducting devices. Here, we analyze the local and nonlocal differential conductance of Coulomb-blockaded multiterminal superconducting islands that host subgap states with different spatial structures. The emerging patterns of their transport spectroscopy are used to characterize the possible topological nature of these devices and offer the possibility of controlling their transport properties. We develop a next-to-leading order master equation to describe the multiterminal transport in superconductors with both strong Coulomb interactions and multiple subgap states, coupled with metallic leads. We show that the nonlocal differential conductance characterizes the spatial extension of the subgap states and signals the presence of degenerate bound states with a finite support on different parts of the device. Additionally, it displays sharp sign changes as a function of the induced charge of the superconductor, signaling energy crossings among its lowest excited states.

14 pages, 7 figures

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Cited by in corpus (8)

• Majorana modes in quantum dots coupled via a floating superconducting island
• Simulations of the dynamics of quantum impurity problems with matrix product states
• Supercurrent transport through 1$e$-periodic full-shell Coulomb islands
• Subgap transport in superconductor--semiconductor hybrid islands: Weak and strong coupling regimes
• Transport in a periodically driven tilted lattice via the extended reservoir approach: Stability criterion for recovering the continuum limit
• The topological Kondo model out of equilibrium
• Fate of the superconducting state in floating islands of hybrid nanowire devices
• Conductance asymmetry in proximitized magnetic topological insulator junctions with Majorana modes