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Svend-Age Biehs

Publications and source records attributed to Svend-Age Biehs.

At least 19 recordsLinked to original sources
arXiv2026

Substrate-driven topological engineering in plasmonic Su-Schrieffer-Heeger chains

We demonstrate the possibility of engineering the topological band structure of a plasmonic Su-Schrieffer-Heeger (SSH) chain through the interaction with its electromagnetic environment. We find that the long-range interaction of the in-plane modes of the SSH chain with the surface plasmon polaritons of a planar substrate introduces a band hybridization connected to a change of the Zak phase. On the other hand, the short-range interaction with the substrate introduces a band touching, again with a change in the Zak phase. Surprisingly, this second mechanism enables the emergence of topologically protected edge modes for parameters which correspond to the topologically trivial phase for an isolated plasmonic SSH chain. We study these mechanisms by changing the chain-substrate distance and the dimerization parameter. Finally, we discuss the robustness against disorder and, as one example, the impact of the observed effects on the near-field radiative heat transfer and the local density of states along the chain. Our findings pave the way to the engineering of edge modes in plasmonic topological configurations via the coupling to a plasmonic environment.

cond-mat.mes-hall↗
arXiv2025

Feynman paradox induced by vacuum and thermal fluctuations

A charged particle initially at rest in an external magnetic field starts to rotate when the magnetic field is switched off. This is a variant of the Feynman disc paradox, where the conservation of angular momentum is seemingly violated. The paradox is understood by realizing that angular momentum is initially stored in the electromagnetic field and is transferred to the particle when the magnetic field is removed. In a classical description, no rotation occurs if the particle is uncharged, as the initial angular momentum is zero in this case. We show that electromagnetic fluctuations in thermal equilibrium can induce a quantum analog of the Feynman paradox, where a nonreciprocal particle without charge starts to rotate when the source of nonreciprocity is removed. This paradox is due to persistent energy fluxes arising in nonreciprocal systems at equilibrium, leading to angular momentum stored in the electromagnetic field. We demonstrate that the contribution of vacuum fluctuations to persistent energy fluxes dominate over thermal fluctuations at finite temperature, so vacuum fluctuations dominate the equilibrium angular momentum as well. Observation of the induced motion would thus provide a means of detecting persistent energy fluxes and offer further evidence for the physical reality of vacuum fluctuations.

cond-mat.mes-hall↗
arXiv2025

Transition from near-field to extreme near-field radiative heat transfer

The radiative heat transfer in the extreme near-field regime, i.e. for distances below 10 nm, remains poorly understood. There are competing experimental results in this regime, with some in good agreement with theoretical predictions, while others report drastically elevated heat fluxes, orders of magnitude larger than what theory suggests. Whether the theory of fluctuational electrodynamics can predict the radiative heat transfer in this extreme near-field regime or not remains a matter of active debate. In this study, a radiative heat transfer measurement is presented between a gold-coated sphere and a gold film sample in the transition regime between the near-field and the extreme near-field regime just before contact. The radiative heat flux measurement is made by using a near-field scanning thermal microscope equipped with a temperature sensor at a sharp tip as a heat flux sensor. We find an excellent agreement with the theoretical predictions of fluctuational electrodynamics in the near-field regime. In the extreme near-field regime however, a highly increased radiative heat flux is observed with values about 100 times larger than the theoretical predictions, indicating that fluctuational electrodynamics fails to capture the radiative heat flux in this regime.

cond-mat.mes-hall↗
arXiv2025

On persistent energy currents at equilibrium in non-reciprocal systems

We investigate the properties of the mean Poynting vector in global thermal equilibrium, which can be non-zero in non-reciprocal electromagnetic systems. Using dyadic Green's functions and the fluctuation-dissipation theorem, we provide a general proof that the mean Poynting vector is divergence-free under equilibrium conditions. Relying on this proof, we explicitly demonstrate that for systems where a normal mode expansion of the Green's function is applicable, the divergence of the equilibrium mean Poynting vector vanishes. As concrete examples, we also examine the equilibrium mean Poynting vector near a planar non-reciprocal substrate and in configurations involving an arbitrary number of dipolar non-reciprocal objects in free space. Finally, we argue that the so-called persistent heat current, while present in equilibrium, cannot be detected through out-of-equilibrium heat transfer measurements.

cond-mat.mes-hall↗
arXiv2025

Roadmap on Nonlocality in Photonic Materials and Metamaterials

Photonic technologies continue to drive the quest for new optical materials with unprecedented responses. A major frontier in this field is the exploration of nonlocal (spatially dispersive) materials, going beyond the local, wavevector-independent assumption traditionally made in optical material modeling. On one end, the growing interest in plasmonic, polaritonic and quantum materials has revealed naturally occurring nonlocalities, emphasizing the need for more accurate models to predict and design their optical responses. This has major implications also for topological, nonreciprocal, and time-varying systems based on these material platforms. Beyond natural materials, artificially structured materials--metamaterials and metasurfaces--can provide even stronger and engineered nonlocal effects, emerging from long-range interactions or multipolar effects. This is a rapidly expanding area in the field of photonic metamaterials, with open frontiers yet to be explored. In the case of metasurfaces, in particular, nonlocality engineering has become a powerful tool for designing strongly wavevector-dependent responses, enabling enhanced wavefront control, spatial compression, multifunctional devices, and wave-based computing. Furthermore, nonlocality and related concepts play a critical role in defining the ultimate limits of what is possible in optics, photonics, and wave physics. This Roadmap aims to survey the most exciting developments in nonlocal photonic materials, highlight new opportunities and open challenges, and chart new pathways that will drive this emerging field forward--toward new scientific discoveries and technological advancements.

cond-mat.mes-hall↗
arXiv2024

Goos-Hänchen effect singularities in transdimensional plasmonic films

We identify and classify topologically protected singularities for the reflection coefficient of transdimensional plasmonic systems. Originating from nonlocal electromagnetic response due to vertical electron confinement in the system, such singularities lead to lateral (angular) Goos-Hänchen shifts on the millimeter (milliradian) scale in the visible range, greatly exceeding those reported previously for artificially designed metasurfaces, offering new opportunities for quantum material development.

physics.optics↗
arXiv2023

Local density of states above a disk -- geometrical vs. thermal boundary conditions

We analytically calculate the contribution to the local density of states due to thermal sources in a disk-like patch within the framework of fluctuational electrodynamics. We further introduce a wavevector cutoff method to approximate this contribution. We compare the results obtained with the source and cutoff method with the numerical exact LDOS above a metal disk attained by SCUFF-EM calculations. By this comparison we highlight the difference and resemblance of thermal and geometrical boundary conditions which are both relevant for near-field scanning microscope measurements. Finally, we give an outlook to general lateral temperature profiles and compare it with surface profiles.

cond-mat.mes-hall↗
arXiv2022

Far- and Near-Field Heat Transfer in Transdimensional Plasmonic Film Systems

We compare the confinement-induced nonlocal electromagnetic response model to the standard local Drude model routinely used in plasmonics. Both of them are applied to study the heat transfer for transdimensional plasmonic film systems. The former provides greater Woltersdorff length in the far-field and larger film thicknesses at which heat transfer is dominated by surface plasmons, leading to enhanced near-field heat currents. Our results show that the nonlocal response model is capable of making a significant impact on the understanding of the radiative heat transfer in ultrathin films.

cond-mat.mes-hall↗
arXiv2022

Heat transfer mediated by the Berry-phase in non-reciprocal many-body systems

We investigate the adiabatic evolution of thermal state in non-reciprocal many-body systems coupled to their environment and subject to periodic drivings. In such systems we show that besides the dynamical phase a geometrical phase can exist and it drives the relaxation dynamic of the system. On the contrary to the dynamical phase which always pushes the system toward its equilibrium state we show that the geometric phase can speed up or reduce the speed of relaxation process. These results could have applications in the field of thermal management of complex systems.

quant-ph↗
arXiv2022

Thermal radiation and near-field thermal imaging of a plasmonic Su-Schrieffer-Heeger chain

We investigate the direct thermal emission spectrum of a plasmonic Su-Schrieffer-Heeger chain of InSb nanoparticles as well as its far-field emission due to near-field scattering by a sharp tip as it is used in scattering type thermal microscopes. We discuss the measurability of the topological phase transition in such far-field and near-field experiments and highlight the signatures of the topological edge modes. We further discuss the impact of a substrate.

cond-mat.mes-hall↗
arXiv2022

Generalized coupled dipole method for thermal far-field radiation

We introduce a many body theory for thermal far-field emission of dipolar dielectric and metallic nanoparticles in the vicinity of a substrate within the framework of fluctuational electrodynamics. Our theoretical model includes the possibility to define the temperatures of each nanoparticle, the substrate temperature, and the temperature of the background thermal radiation, separately. To demonstrate the versatility of our method, we apply it in an exemplary way by discussing the thermal radiation of four particle assemblies of SiC and Ag nanoparticles above a planar SiC and Ag substrate. Furthermore, we use discrete dipole approximation to determine the thermal emission of a spherical nanoparticle in free space and close to a substrate. Finally, the calculation of the thermal far-field radiation of a sharp Si tip close to a SiC substrate using the discrete dipole approximation including the near-field scattering by the tip as well as the thermal emission of the tip and the contribution of the substrate which is partially blocked by the tip serves as another example.

physics.optics↗
arXiv2022

Topological near-field heat flow in a honeycomb lattice

We study the near-field thermal radiation of topologically protected edge modes in a honeycomb lattice of plasmonic InSb nanoparticles. We show that the heat transport by near-field interaction is in the topological non-trivial phase dominated by the heat flux channel provided by the edge modes rather than the bulk modes. This heat flux channel allows for an enhanced heat transport along the edges of the honeycomb lattice. In particular for materials with relatively small dissipation we find a 30 to 50 times larger heat flux along the lattice edges than in the bulk.

cond-mat.mes-hall↗
arXiv2021

Thermal near-field energy density and LDOS in topological 1D SSH chains and 2D SSH lattices of plasmonic nanoparticles

We derive a general expression for electric and magnetic part of the near-field energy density of $N$ dipoles of temperatures $T_1, \ldots, T_N$ immersed in a background field having a different temperature $T_b$. In contrast to former expressions this inclusion of the background field allows for determining the energy density of heated or cooled isotropic dipolar objects within an arbitrary environment which is thermalized at a different temperature. Furthermore, we show how the energy density is related to the local density of states. We use this general expression to study the near-field enhanced energy density at the edges and corners of 1D Su-Schrieffer-Heeger chains and 2D Su-Schrieffer-Heeger lattices of plasmonic InSb nanoparticles when the phase transition from a topological trivial to a topological non-trivial state is made. We discuss the robustness of these modes when adding defects and the possibility to measure the topological edge and corner modes.

cond-mat.mes-hall↗
arXiv2021

Smart thermal management with near-field thermal radiation

When two objects at different temperatures are separated by a vacuum gap they can exchange heat by radiation only. At large separation distances (far-field regime) the amount of transferred heat flux is limited by Stefan-Boltzmann's law (blackbody limit). In contrast, at subwavelength distances (near-field regime) this limit can be exceeded by orders of magnitude thanks to the contributions of evanescent waves. This article reviews the recent progress on the passive and active control of near-field radiative heat exchange in two- and many-body systems.

physics.class-ph↗
arXiv2021

Radiative thermal switch exploiting hyperbolic surface phonon polaritons

We study the radiative heat flux between two nanoparticles in close vicinity to the natural hyperbolic material hBN with its optical axis oriented parallel to the interface. We show that the heat flux between the nanoparticles can be efficiently modulated when rotating the nanoparticles due to the coupling to the highly directional hyperbolic surface modes in hBN. Finally, we discuss the thickness and distance dependence of this effect.

cond-mat.mes-hall↗
arXiv2021

Radiative cooling induced by time-symmetry breaking in periodically-driven systems

We theoretically study the thermal relaxation of many-body systems under the action of oscillating external fields. When the magnitude or the orientation of a field is modulated around values where the pairwise heat-exchange conductances depend non-linearly on this field, we demonstrate that the time symmetry is broken during the evolution of temperatures over a modulation cycle. We predict that this asymmetry enables a pumping of heat which can be used to cool down faster the system. This effect is illustrated through different magneto-optical systems under the action of an oscillating magnetic field.

cond-mat.mes-hall↗
arXiv2021

Dipole model for far-field thermal emission of a nanoparticle above a planar substrate

We develop a dipole model describing the thermal far-field radiation of a nanoparticle in close vicinity to a substrate. By including in our description the contribution of eddy currents and the possibility to choose different temperatures for the nanoparticle, the substrate, and the background, we generalize the existing models. We discuss the impact of the different temperatures, particle size, emission angle, and the distance dependence for all four combinations of gold and SiC nanoparticles or substrates.

cond-mat.mes-hall↗