Solar Energy Conversion by Nanostructured TiO2

Research in solar energy conversion and the associated photoactive materials has attracted continuous interest. Due to its proper electronic band structure, high quantum efficiency, and photonic and chemical innerness, TiO2 has been demonstrated as a versatile oxide semiconductor capable of efficiently utilizing sunlight to produce electrical and chemical energy. Its outstanding physicochemical performances have led to an array of advanced photocatalytic and photoelectrochemical applications including environmental photocatalysis, dye/semiconductor-sensitized solar cell, and solar fuel productions.

Quantum Otto heat engine based on a multiferroic chain working substance

We study a quantum Otto engine operating on the basis of a helical spin-1/2 multiferroic chain with strongly coupled magnetic and ferroelectric order parameters. The presence of a finite spin chirality in the working substance enables steering of the cycle by an external electric field that couples to the electric polarization. We observe a direct connection between the chirality, the entanglement and the efficiency of the engine. An electric-field dependent threshold temperature is identified, above which the pair correlations in the system, as quantified by the thermal entanglement, diminish. In contrast to the pair correlations, the collective many-body thermal entanglement is less sensitive to the electric field, and in the high temperature limit converges to a constant value. We also discuss the correlations between the threshold temperature of the pair entanglement, the spin chirality and the minimum of the fidelities in relation to the electric and magnetic fields. The efficiency of the quantum Otto cycle shows a saturation plateau with increasing electric field amplitude.