Realization of finite-rate isothermal compression and expansion using optical feedback trap

John A.C. Albay, Pik Yin Lai, Yonggun Jun

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9 Scopus citations


We experimentally realize the finite-rate isothermal process of a Brownian particle in a breathing harmonic potential. For the compression process, finite-rate equilibration can be achieved by increasing and then decreasing the stiffness of the potential to the final stiffness according to the shortcuts-to-isothermal (ScI) protocol. On the other hand, the realization of the ScI expansion is experimentally impossible with optical tweezers due to the requirement of a negative stiffness. Here, we propose a simple and elegant method to resolve this problem and demonstrate the ScI expansion by using the optical feedback trap capable of creating an arbitrary spatiotemporal potential even with a negative stiffness. In addition, we check the thermodynamic energetics such as work, heat, and internal energy, which indeed obey stochastic thermodynamics. Our method provides the possibility of a Brownian heat engine with maximum efficiency but non-vanishing power.

Original languageEnglish
Article number103706
JournalApplied Physics Letters
Issue number10
StatePublished - 9 Mar 2020


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