We demonstrate that nonequilibrium nanoscopic systems with Majorana zero modes admit a special kind of universality which cannot be classified as strictly transport or strictly thermodynamic in nature. To reveal such a type of Majorana universality we explore purely thermal nonequilibrium states of a quantum dot whose low-energy degrees of freedom are governed by Majorana zero modes. Specifically, the quantum dot is coupled to a topological superconductor, supporting Majorana zero modes, as well as to two normal metallic contacts with the same chemical potentials but different temperatures. It is shown that the Majorana universality in this setup is dual: it is stored inside both the response of the electric current, excited exclusively by the temperature difference, and the quantum dot compressibility. The latter is defined as the derivative of the quantum dot particle number with respect to the chemical potential and forms a universal Majorana ratio with a proper derivative of the electric current that flows in nonequilibrium states of a purely thermal nature.

• Received 17 December 2019
• Revised 24 February 2020
• Accepted 26 February 2020

DOI:https://doi.org/10.1103/PhysRevB.101.125417