Charge-4e superconductors: a Majorana quantum Monte Carlo study

Understand

Many features of charge-4e superconductors remain unknown because even the "mean-field Hamiltonian" describing them is an interacting model.

• Here we introduce an interacting model to describe a charge-4e superconductor (SC) deep in the superconducting phase, and explore its properties using quantum Monte Carlo (QMC) simulations.
• The QMC is sign-problem-free, but only when a Majorana representation is employed.
• As a function of the chemical potential we observe two sharply-distinct behaviors: a "strong" quarteting phase in which charge-4e quartets are tightly bound (like molecules) so that charge-2e pairing does not occur even in the temperature $T \to 0$ limit, and a "weak" quarteting phase in which a further transition to a charge-2e superconducting phase occurs at a lower critical temperature.