Quantum thermodynamics of quantum critical systems

• Autor(a) principal: Adalberto Deybe Varizi
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/45188; https://orcid.org/0000-0003-2322-4499
• topic: Quantum thermodynamics; Quantum phase transitions; Critical phenomena; Quantum coherences; Entropy production; Splittings of entropy production; Ising model; Entropia; Termodinâmica; Transições de fase; Fenômenos críticos; Modelo de Ising

This thesis is devoted to the study of systems presenting continuous quantum phase transitions subject to a thermodynamic work protocol. Particularly, we investigated how quantum coherences created by a sudden change in the system Hamiltonian can be quantified and their relation to its critical behavior. Therefore, the results here presented lie within the scope of quantum thermodynamics. The effects of quantum criticality in work protocols have been considerably investigated in recent years. Still, little or nothing was known about the role of quantum coherences. To grasp this, we examined two splittings of entropy production into a classical and quantum parts, the latter related to quantum coherences. The first splitting have been used in several contexts and maintains an intimate connection with the resource theory of thermodynamics. However, employing it to a quantum Ising model driven out of equilibrium by a sudden quench, we verified some shortcomings: namely, counter-intuitive and immutable behavior at low temperatures and unexpected nonanalyticities unrelated to critical phenomena. This inspired us to introduce a new and complementary separation to the entropy produced following a work protocol. A surprising and intriguing property of these splittings when applied to critical systems is the fact that they exhibit signatures of the critical point independently of the system initial temperature. In the new splitting we are capable of explaining this as a consequence of their close relation to the derivatives of the energy spectrum.