Quantum Critical Engine at Finite Temperatures: Many Body Quantum Otto Cycle

Table of Links

Abstract and 1 Introduction

2 Free fermionic model

3 Many body quantum Otto cycle

4 Universal scalings in work output

5 Transverse Ising model as working medium

6 Conclusion and References

3 Many body quantum Otto cycle

We now describe the quantum Otto cycle (QOC) which consist of four strokes (also shown in Fig.1):

(ii) Stroke B → C: The WM is disconnected from the hot bath and α is changed from α1 to α2 using the driving protocol,

The evolution being a unitary evolution is given by the von-Neumann equation of motion:

In this work, we shall focus on α2 = αc, the critical value, for the reasons that will be explained later.

(iii) Stroke C → D: The WM with α = α2 is next connected to the cold bath at a temperature TC till τC so that it reaches the thermal state at D given by

(iv) Stroke D → A: In this last stroke, the WM is disconnected from the cold bath, and α is changed back to α1 from α2 using

to reach A through unitary dynamics and thus the cycle repeats.

Energies at the end of each stroke i is calculated using the equation

We characterize the engine performance using the quantities efficiency and power which are computed as