1,721,008 research outputs found
Coulomb drag and Dirac plasmons in novel 2D electron systems
No full text[from the introduction]: This Thesis focusses on
the physics of e-e interactions in single-layer graphene and on the role of interlayer e-e
interactions in vertical heterostructures comprised of two closely spaced graphene sheets
Synchronization-induced violation of thermodynamic uncertainty relations
Full text linkFluctuations affect the functionality of nanodevices. Thermodynamic uncertainty relations (TURs), derived within the framework of stochastic thermodynamics, show that a minimal amount of dissipation is required to obtain a given relative energy current dispersion, that is, current precision has a thermodynamic cost. It is therefore of great interest to explore the possibility that TURs are violated, particularly for quantum systems, leading to accurate currents at lower cost. Here, we show that two quantum harmonic oscillators are synchronized by coupling to a common thermal environment, at strong dissipation and low temperature. In this regime, periodically modulated couplings to a second thermal reservoir, breaking time-reversal symmetry and taking advantage of non-Markovianity of this latter reservoir, lead to strong violation of TURs for local work currents, while maintaining finite output power. Our results pave the way for the use of synchronization in the thermodynamics of precision
Interference-induced thermoelectric switching and heat rectification in quantum Hall junctions
No full textInterference represents one of the most striking manifestations of quantum physics in low-dimensional systems. Despite evidence of quantum interference in charge transport having been known for a long time, signatures of interference-induced thermal properties have been reported only recently, paving the way for the phase-coherent manipulation of heat in mesoscopic devices. In this work we show that anomalous thermoelectric properties and efficient heat rectification can be achieved by exploiting the phase-coherent edge states of quantum Hall systems. By considering a tunneling geometry with multiple quantum point contacts, we demonstrate that the interference paths effectively break the electron-hole symmetry, allowing for a thermoelectric charge current flowing either from hot to cold or vice versa, depending on the details of the tunnel junction. Correspondingly, an interference-induced heat current is predicted, and we are able to explain these results in terms of an intuitive physical picture. Moreover, we show that heat rectification can be achieved by coupling two quantum Hall systems with different filling factors, and that this effect can be enhanced by exploiting the interference properties of the tunnel junction
Dissipation-induced collective advantage of a quantum thermal machine
Full text linkDo quantum correlations lead to better performance with respect to several
different systems working independently? For quantum thermal machines, the
question is whether a working medium (WM) made of constituents exhibits
better performance than independent engines working in parallel. Here, by
inspecting a microscopic model with the WM composed by two non-interacting
quantum harmonic oscillators, we show that the presence of a common environment
can mediate non-trivial correlations in the WM leading to better quantum heat
engine performance -- maximum power and efficiency -- with respect to an
independent configuration. Furthermore, this advantage is striking for strong
dissipation, a regime in which two independent engines cannot deliver any
useful power. Our results show that dissipation can be exploited as a useful
resource for quantum thermal engines, and are corroborated by optimization
techniques here extended to non-Markovian quantum heat engines.Comment: Accepted Manuscript: Main text (13 pages, 8 figures) + Supplementary
Material (9 pages, 3 figures). This article may be downloaded for personal
use only. Any other use requires prior permission of the author and AIP
Publishing. This article appeared in AVS Quantum Science 6, 025001 (2024) and
may be found at https://doi.org/10.1116/5.019034
Spectral features of voltage pulses in interacting helical channels
Full text linkWe investigate the interplay of voltage-driven excitations and electron-electron interactions in a pair of counterpropagating helical channels capacitively coupled to a time-dependent gate. By focusing on the non-equilibrium spectral properties of the system, we show how the spectral function is modified by external drives with different time profile in presence of Coulomb interactions. In particular, we focus on a Lorentzian drive and a square single pulse. In presence of strong enough electron-electron interactions, we find that both drives can result in minimal excitations, i.e. characterized by an excess spectral function with a definite sign. This is in contrast with what happens in the non-interacting case, where only properly quantized Lorentzian pulses are able to produce minimal excitations
Spin-thermoelectric transport induced by interactions and spin-flip processes in two dimensional topological insulators
Full text linkpeer reviewe
Efficiency and thermodynamic uncertainty relations of a dynamical quantum heat engine
Full text linkIn the quest for high-performance quantum thermal machines, looking for an optimal thermodynamic efficiency is only part of the issue. Indeed, at the level of quantum devices, fluctuations become extremely relevant and need to be taken into account. In this paper we study the thermodynamic uncertainty relations for a quantum thermal machine with a quantum harmonic oscillator as a working medium, connected to two thermal baths, one of which is dynamically coupled. We show that parameters can be found such that the machine operates both as a quantum engine or refrigerator, with both sizeable efficiency and small fluctuations.16 pages, 5 color figures. This version of the article has been accepted for publication, after peer review but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1140/epjs/s11734-023-00949-
Covariant field theory of 3D massive fractons
No full textAbstract We construct a covariant and gauge-invariant theory describing massive fractons in three spacetime dimensions, based on a symmetric rank-2 tensor field. The model includes a Chern–Simons-like term that plays a dual role: it generates a topological mass for the tensor gauge field and simultaneously acts as a source of intrinsic fractonic matter. This dual mechanism is novel and leads to a propagating fractonic degree of freedom described by a massive Klein–Gordon equation. The theory propagates two degrees of freedom – one massive, one massless – whose number is preserved in the massless limit, in analogy with the Maxwell–Chern–Simons mechanism of Deser–Jackiw–Templeton. We analyze the resulting equations of motion and show that the intrinsic fractonic matter satisfies Gauss- and Ampère-like laws, with conserved dipole and trace of the quadrupole moment. Upon coupling to external matter, a second fractonic sector emerges, leading to a coexistence of intrinsic and extrinsic subsystems with different mobility and conservation properties. Our model provides a unified framework for describing massive fractons with internal structure, and offers a covariant setting for exploring their interactions and extensions
Time-resolved energy dynamics after single electron injection into an interacting helical liquid
Full text linkpeer reviewedThe possibility of injecting a single electron into ballistic conductors is at the basis of the new field of electron quantum optics. Here, we consider a single electron injection into the helical edge channels of a topological insulator. Their counterpropagating nature and the unavoidable presence of electron-electron interactions dramatically affect the time evolution of the single wave packet. Modeling the injection process from a mesoscopic capacitor in the presence of nonlocal tunneling, we focus on the time-resolved charge and energy packet dynamics. Both quantities split up into counterpropagating contributions whose profiles are strongly affected by the interaction strength. In addition, stronger signatures are found for the injected energy, which is also affected by the finite width of the tunneling region, in contrast to what happens for the charge. Indeed, the energy flow can be controlled by tuning the injection parameters, and we demonstrate that, in the presence of nonlocal tunneling, it is possible to achieve a situation in which charge and energy flow in opposite directions
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