| 1. |
- Acciai, Matteo, 1992, et al.
(författare)
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Constraints between entropy production and its fluctuations in nonthermal engines
- 2024
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 109:7
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Tidskriftsartikel (refereegranskat)abstract
- We analyze a mesoscopic conductor autonomously performing a thermodynamically useful task, such as cooling or producing electrical power, in a part of the system - the working substance - by exploiting another terminal or set of terminals - the resource - that contains a stationary nonthermal (nonequilibrium) distribution. Thanks to the nonthermal properties of the resource, on average no exchange of particles or energy with the working substance is required to fulfill the task. This resembles the action of a demon, as long as only average quantities are considered. Here, we go beyond a description based on average currents and investigate the role of fluctuations in such a system. We show that a minimum level of entropy fluctuations in the system is necessary, whenever one is exploiting a certain entropy production in the resource terminal to perform a useful task in the working substance. For concrete implementations of the demonic nonthermal engine in three- and four-terminal electronic conductors in the quantum Hall regime, we compare the resource fluctuations to the entropy production in the resource and to the useful engine output (produced power or cooling power).
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| 2. |
- Acciai, Matteo, 1992, et al.
(författare)
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Influence of channel mixing in fermionic Hong-Ou-Mandel experiments
- 2022
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 105:12
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Tidskriftsartikel (refereegranskat)abstract
- We consider an electronic Hong-Ou-Mandel interferometer in the integer quantum Hall regime, where the colliding electronic states are generated by applying voltage pulses (creating for instance levitons) to ohmic contacts. The aim of this work is to investigate possible mechanisms leading to a reduced visibility of the Pauli dip, i.e., the noise suppression expected for synchronized sources. It is known that electron-electron interactions cannot account for this effect and always lead to a full suppression of the Hong-Ou-Mandel noise. Focusing on the case of filling factor ?=2, we show instead that a reduced visibility of the Pauli dip can result from mixing of the copropagating edge channels, arising from tunneling events between them.
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| 3. |
- Acciai, Matteo, 1992, et al.
(författare)
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Phase-coherent heat circulators with normal or superconducting contacts
- 2021
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 103:8
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Tidskriftsartikel (refereegranskat)abstract
- We investigate heat circulators where a phase coherent region is contacted by three leads that are either normal- or superconducting. A magnetic field, and potentially the superconducting phases, allow to control the preferential direction of the heat flow between the three-different temperature-biased contacts. The main goal of this study is to analyze the requirements for heat circulation in nonideal devices, in particular focusing on sample-to-sample variations. Quite generally, we find that the circulation performance of the devices is good as long as only a few transport channels are involved. We compare the performance of circulators with normal conducting contacts to those with superconducting contacts and find that the circulation coefficients are essentially unchanged.
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| 4. |
- Adak, Vivekananda, et al.
(författare)
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Spin Berry phase in a helical edge state : S-z nonconservation and transport signatures
- 2020
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 102:3
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Tidskriftsartikel (refereegranskat)abstract
- Topological protection of edge state in quantum spin Hall systems relies only on time-reversal symmetry. Hence, S-z conservation on the edge can be relaxed which can have an interferometric manifestation in terms of spin Berry phase. Primarily it could lead to the generation of spin Berry phase arising from a closed loop dynamics of electrons. Our work provides a minimal framework to generate and detect these effects by employing both spin-unpolarized and spin-polarized leads. We show that spin-polarized leads could lead to resonances or antiresonances in the two-terminal conductance of the interferometer. We further show that the positions of these antiresonances (as a function of energy of the incident electron) get shifted owing to the presence of spin Berry phase. Finally, we present simulations of a device setup using KWANT package which put our theoretical predictions on a firm footing.
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| 5. |
- Ageev, Dmitry S., et al.
(författare)
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Deterministic chaos and fractal entropy scaling in Floquet conformal field theories
- 2021
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 103:10
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we study two-dimensional Floquet conformal field theory, where the external periodic driving is described by iterated logistic or tent maps. These maps are known to be typical examples of dynamical systems exhibiting the order-chaos transition, and we show that, as a result of such driving, the entanglement entropy scaling develops fractal features when the corresponding dynamical system approaches the chaotic regime. For the driving set by the logistic map, the fractal contribution to the scaling dominates, making entanglement entropy a highly oscillating function of the subsystem size.
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| 6. |
- Ahmed, Aamna, et al.
(författare)
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Flat band based multifractality in the all-band-flat diamond chain
- 2022
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 106:20
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Tidskriftsartikel (refereegranskat)abstract
- We study the effect of quasiperiodic Aubry-Andre disorder on the energy spectrum and eigenstates of a one-dimensional all-band-flat (ABF) diamond chain. The ABF diamond chain possesses three dispersionless flat bands with all the eigenstates compactly localized on two unit cells in the zero disorder limit. The fate of the compact localized states in the presence of the disorder depends on the symmetry of the applied potential. We consider two cases here: a symmetric one, where the same disorder is applied to the top and bottom sites of a unit cell and an antisymmetric one, where the disorder applied to the top and bottom sites are of equal magnitude but with opposite signs. Remarkably, the symmetrically perturbed lattice preserves compact localization, although the degeneracy is lifted. When the lattice is perturbed antisymmetrically, not only is the degeneracy is lifted but compact localization is also destroyed. Fascinatingly, all eigenstates exhibit a multifractal nature below a critical strength of the applied potential. A central band of eigenstates continue to display an extended yet nonergodic behavior for arbitrarily large strengths of the potential. All other eigenstates exhibit the familiar Anderson localization above the critical potential strength. We show how the antisymmetric disordered model can be mapped to a pi /4 rotated square lattice with the nearest and selective next-nearest-neighbor hopping and a staggered magnetic field-such models have been shown to exhibit multifractality. Surprisingly, the antisymmetric disorder (with an even number of unit cells) preserves chiral symmetry-we show this by explicitly writing down the chiral operator.
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| 7. |
- Aksoy, Omer M., et al.
(författare)
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Single monkey-saddle singularity of a Fermi surface and its instabilities
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 107:20
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Tidskriftsartikel (refereegranskat)abstract
- Fermi surfaces can undergo sharp transitions under smooth changes of parameters. Such transitions can have a topological character, as is the case when a higher-order singularity, one that requires cubic or higher-order terms to describe the electronic dispersion near the singularity, develops at the transition. When time-reversal and inversion symmetries are present, odd singularities can only appear in pairs within the Brillouin zone. In this case, the combination of the enhanced density of states that accompanies these singularities and the nesting between the pairs of singularities leads to interaction-driven instabilities. We present examples of single n = 3 (monkeysaddle) singularities when time-reversal and inversion symmetries are broken. We then turn to the question of what instabilities are possible when the singularities are isolated. For spinful electrons, we find that the inclusion of repulsive interactions destroys any isolated monkey-saddle singularity present in the noninteracting spectrum by developing Stoner or Lifshitz instabilities. In contrast, for spinless electrons and at the mean-field level, we show that an isolated monkey-saddle singularity can be stabilized in the presence of short-range repulsive interactions.
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| 8. |
- Amundsen, Morten, et al.
(författare)
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Magnonic spin Joule heating and rectification effects
- 2022
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 106:14
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Tidskriftsartikel (refereegranskat)abstract
- Nonlinear devices, such as transistors, enable contemporary computing technologies. We theoretically investigate nonlinear effects, bearing a high fundamental scientific and technical relevance, in magnonics with emphasis on superconductor-ferromagnet hybrids. Accounting for a finite magnon chemical potential, we theoretically demonstrate magnonic spin Joule heating, the spin analog of conventional electronic Joule heating. Besides suggesting a key contribution to magnonic heat transport in a broad range of devices, it provides insights into the thermal physics of nonconserved bosonic excitations. Considering a spin-split superconductor self-consistently, we demonstrate its interface with a ferromagnetic insulator to harbor large tunability of spin and thermal conductances. We further demonstrate hysteretic rectification I-V characteristics in this hybrid, where the hysteresis results from the superconducting state bistability.
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| 9. |
- Andrade, Tomas, et al.
(författare)
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Thermoelectric transport properties of gapless pinned charge density waves
- 2022
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 106:4
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Tidskriftsartikel (refereegranskat)abstract
- Quantum strongly correlated matter exhibits properties which are not easily explainable in the conventional framework of Fermi liquids. Universal effective field theory tools are applicable in these cases regardless of the microscopic details of the quantum system, since they are based on symmetries. It is necessary, however, to construct these effective tools in full generality, avoiding restrictions coming from particular microscopic descriptions which may inadequately constrain the coefficients that enter in the effective theory. In this work we demonstrate with explicit examples how the hydrodynamic coefficients, which have been recently reinstated in the effective theory of pinned charge density waves (CDWs), can affect the phenomenology of the thermoelectric transport in strongly correlated quantum matter. Our examples, based on two classes of holographic models with pinned CDW, have microscopics which are conceptually different from Fermi liquids. Therefore, the above transport coefficients are nonzero, contrary to the conventional approach. We show how these coefficients allow one to take into account the change of sign of the Seebeck coefficient and the low resistivity of the CDW phase of the cuprate high temperature superconductors, without referring to the effects of Fermi surface reconstruction.
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| 10. |
- Anghel,, et al.
(författare)
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Electromagnetic radiation detectors based on Josephson junctions: Effective Hamiltonian
- 2020
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 101:2
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically analyze two setups of low-energy single-photon counters based on Josephson junctions (JJs). For this, we propose two simple and general models based on the macroscopic quantum tunneling formalism (MQT). The first setup is similar to the photon counter based on the "cold-electron bolometer" (CEB), where the JJ replaces the CEB in the center of the superconducting antenna. In the second setup, the JJ is capacitively coupled to the antenna. We derive the Hamiltonians for the two setups, and we write the Schrodinger equations, taking into account both the antenna and the JJ. The quantum particles of the MQT models move in two-dimensional potential landscapes, which are parabolic along one direction and may have the form of a washboard potential along another direction. Such a potential landscape has a series of local minima, separated by saddle points. If the particle is prepared in the initial state in the metastable "ground state" of a local minimum, then the photon absorption causes it to jump into an excited state. If the excitation energy is bigger than the potential barrier seen by the quantum particle (the difference between the ground state and the saddle point), the photon is detected. The models are simple and allow us to do mostly analytical calculations. We show that the two setups are equivalent from the MQT point of view since one Hamiltonian can be transformed into the other by changes in variables. For typical values of the JJ and antenna parameters, the setups may work as counters of photons of wavelengths up to at least 1 cm. Dark count rates due to the phase particle tunneling directly from the ground state into the running state have also been evaluated.
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