Quantum control of excitons for reversible heat transfer

Abstract

Lasers, photovoltaics, and thermoelectrically-pumped light emitting diodes are thermodynamic machines which use excitons (electron-hole pairs) as the working medium. The heat transfers in such devices are highly irreversible, leading to low efficiencies. Here we predict that reversible heat transfers between a quantum-dot exciton and its phonon environment can be induced by laser pulses. We calculate the heat transfer when a quantum-dot exciton is driven by a chirped laser pulse. The reversibility of this heat transfer is quantified by the efficiency of a heat engine in which it forms the hot stroke, which we predict to reach 95% of the Carnot limit. This performance is achieved by using the time-dependent laser-dressing of the exciton to control the heat current and exciton temperature. We conclude that reversible heat transfers can be achieved in excitonic thermal machines, allowing substantial improvements in their efficiency.

Journey of ZnO quantum dots from undoped to rare-earth and transition metal-doped and their applications

“…The phonon peak shi that arises in the ZnO QDs is related to three main factors: phonon localization by defect creation, connement effect within the QD boundaries, and laser-induced heating effect. [49][50][51][52] Alim and his group 53 studied the resonant and nonresonant Raman spectra of ZnO. They found that the E 2 (high) peak shied by 3 cm À1 , which was due to the presence of defects.…”

Quantum control of solid-state qubits for thermodynamic applications

“…ρu evolves according to a modified Hamiltonian, which includes phase factors that serve to keep track of the transfer of energy, or indeed other quantities, to and from the environment. These phase factors appear in the equation-of-motion 14 for ρu , which is otherwise identical to Eq. ( 2).…”

“…12,13 Here, we discuss the exciton-phonon dynamics in a driven quantum dot from the perspective of thermodynamics, and report forms of driving pulse which enable heat to be transferred from the phonons to the exciton. We summarize results from our recent paper 14 for the heat absorption of different pulses, and also the associated entropy generation, which quantifies the extent to which the heat transfer is reversible. These results show that suitable shaping of the frequency profile of the driving allows for near-reversible heat transfers, in effect implementing an isothermal expansion or compression.…”

Quantum heat statistics with time-evolving matrix product operators

“…η α (t, u) ≈ 0 for t > τ C , where τ C is the bath memory time. Therefore, in the discretised form of the modified influence functional (31) one can introduce a maximum value of |k − k | beyond which the coefficients η α k−k (u) are negligible for all u. As a result, we may approximate…”