Research Project: Topolojik Sistemlerde Kuantum Termodinamik
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Contributors
Funders
ID
TB.00328
Authors
Müstecaplıoğlu, Özgür Esat
Faculty Member
Publications
Topological phase transition in quantum-heat-engine cycles
(American Physical Society (APS), 2018) Müstecaplıoğlu, Özgür Esat; Yunt, Elif; Fadaie, Seyedeh Mozhdeh; Department of Physics; Graduate School of Sciences and Engineering; Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
We explore the signatures of a topological phase transition (TPT) in the work and efficiency of a quantum heat engine, which uses a single-layer topological insulator, stanene, in an external electric field as a working substance. The magnitude of the electric field controls the trivial and topological insulator phases of the stanene. The effect of the TPT is investigated in two types of thermodynamic cycles, with and without adiabatic stages. We examine a quantum Otto cycle for the adiabatic case and an idealized Stirling cycle for the nonadiabatic case. In both cycles, investigations are done for high and low temperatures. It is found that the Otto cycle can distinguish the critical point of the TPT as an extremum point in the work output with respect to applied fields at all temperatures. The Stirling cycle can identify the critical point of the TPT as the maximum work point with respect to the applied fields only at relatively lower temperatures. As temperatures increase toward room temperature, the maximum work point of the Stirling cycle shifts away from the critical point of the TPT. In both cycles, increasing the temperature causes considerable enhancement in work and efficiency from the order of meV to eV.
Thermodynamic consistency of the optomechanical master equation
(American Physical Society (APS), 2018) Müstecaplıoğlu, Özgür Esat; Naseem, Muhammad Tahir; Xuereb, Andre; Department of Physics; Graduate School of Sciences and Engineering; Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
We investigate the thermodynamic consistency of the master equation description of heat transport through an optomechanical system attached to two heat baths, one optical and one mechanical. We employ three different master equations to describe this scenario: (i) The standard master equation used in optomechanics, where each bath acts only on the resonator that it is physically connected to; (ii) the so-called dressed-state master equation, where the mechanical bath acts on the global system; and (iii) what we call the global master equation, where both baths are treated nonlocally and affect both the optical and mechanical subsystems. Our main contribution is to demonstrate that, under certain conditions including when the optomechanical coupling strength is weak, the second law of thermodynamics is violated by the first two of these pictures. In order to have a thermodynamically consistent description of an optomechanical system, therefore, one has to employ a global description of the effect of the baths on the system.
Internal geometric friction in a Kitaev-chain heat engine
(American Physical Society (APS), 2020) Müstecaplıoğlu, Özgür Esat; Yunt, Elif; Fadaie, Seyedeh Mozhdeh; Smith, Cristiane Morais; Department of Physics; Graduate School of Sciences and Engineering; Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
We investigate a heat engine with a finite-length Kitaev chain in an ideal Otto cycle. It is found that the critical point of the topological phase transition coincides with the maxima of the efficiency and work output of the total Otto engine. Finite-size effects are taken into account using the method of Hill's nanothermodynamics, as well as using the method of temperature-dependent energy levels. We identify the bulk and boundary thermal cycles of the Kitaev chain engine and find that they are nonideal Otto cycles. The physics of deviation from ideal Otto cycle is identified as a finite-size effect, which we dub as "internal geometric friction,"leading to heat transfer from the bulk to the boundary during the adiabatic transformation of the whole system. In addition, we determine the regimes allowing for independently running an ideal Otto refrigerator at the boundary and ideal Otto engines in the bulk and in the whole system. Furthermore, we show that the first-order phase transition in the boundary and the second-order phase transition in the bulk can be identified through their respective contributions to the engine work output.
