PhD student Luciano Henrique Siliano Ricco at the São Paulo Research Foundation (FAPESP) has proposed using an exotic particle called a Majorana fermion which is made up of a particle and its anti-particle. This is named after a Spanish researcher who proposed the particle in 1937 and such particles have been demonstrated in the laboratory in one dimensional wires.
“We propose a theoretical device that acts as a thermoelectric tuner – a tuner of heat and charge – assisted by Majorana fermions,” said Ricco’s supervisor, Antonio Carlos Ferreira Seridonio.
The proposed device consists of a quantum dot (QD) (ε1, above) located between two metallic leads at different temperatures which allows the thermal energy to flow across the QD.
A one-dimensional superconducting wire – called a Kitaev wire – is connected to the QD, and for this study, the Kitaev wire was ring- or U-shaped and had two Majorana fermion (η1 and η2) at its edges. The Majoranas emerge as excitations characterized by zero-energy modes.
“When the QD is coupled to only one side of the wire, the system behaves resonantly with regard to electrical and thermal conductance. In other words, it behaves like a thermoelectric filter,” said Seridonio.
“I should stress that this behaviour as a filter for thermal and electrical energy occurs when the two majoranas ‘see’ each other via the wire, but only one of them ‘sees’ the QD in the connection.”
Another possibility investigated by the researchers involved making the QD “see” the two majoranas at the same time by connecting it to both ends of the Kitaev wire.
“By making the QD ‘see’ more of η1 or η2, i.e., by varying the system’s asymmetry, we can use the artificial atom as a tuner, where the thermal or electrical energy that flows through it is redshifted or blueshifted,” said Seridonio.
The theoretical paper, published in Scientific Reports, is expected to contribute to the development of nanoscale thermoelectric devices based on Majorana fermions.