-
Quantum Listenings -- Amateur Sonification of Vacuum and other Noises
Authors:
Carsten Henkel
Abstract:
The sensory perceptions of vision and sound may be considered as complementary doorways towards interpreting and understanding physical phenomena. We provide a few selected samples where scientific data of systems usually not directly accessible to humans may be listened to. The examples are chosen close to the regime where quantum mechanics is applicable. Visual and auditory renderings are compar…
▽ More
The sensory perceptions of vision and sound may be considered as complementary doorways towards interpreting and understanding physical phenomena. We provide a few selected samples where scientific data of systems usually not directly accessible to humans may be listened to. The examples are chosen close to the regime where quantum mechanics is applicable. Visual and auditory renderings are compared with some connections to music, illustrating in particular a kind of fractal complexity along the time axis.
△ Less
Submitted 22 December, 2025; v1 submitted 27 June, 2025;
originally announced July 2025.
-
Soft Condensation
Authors:
Ambre Bouillant,
Christopher Henkel,
Uwe Thiele,
Bruno Andreotti,
Jacco H. Snoeijer
Abstract:
When moist air meets a cold surface, it creates a breath figure characterized by numerous small droplets. The central question is how the vapor flux is distributed between the growth of previously condensed drops and the nucleation of new ones. Here, we investigate the nucleation, growth, and coalescence of droplets on soft crosslinked polymer networks. The number of droplets initially remains con…
▽ More
When moist air meets a cold surface, it creates a breath figure characterized by numerous small droplets. The central question is how the vapor flux is distributed between the growth of previously condensed drops and the nucleation of new ones. Here, we investigate the nucleation, growth, and coalescence of droplets on soft crosslinked polymer networks. The number of droplets initially remains constant, until drops start to coarsen according to a universal law; both phenomena are explained via the formation of a saturated boundary layer. Although nucleation occurs at a scale where the polymer network resembles a melt, we quantitatively unveil an algebraic sensitivity of the number of droplets on the substrate elasticity. Our findings suggest that nucleation follows a surprisingly low-energy pathway, influenced by the degree of crosslinking. Consequently, breath figures offer a macroscopic approach to probe the molecular characteristics of the polymer interface.
△ Less
Submitted 10 July, 2024;
originally announced July 2024.
-
Limit on spatial quantum superpositions with massive objects due to phonons
Authors:
Carsten Henkel,
Ron Folman
Abstract:
It has been a long-standing goal to bring massive objects into a superposition of different locations in real space, not only to confirm quantum theory in new regimes, but also to explore the interface with gravity. The main challenge is usually thought to arise from forces or scattering due to environmental fields and particles that decohere the large object's wave function into a statistical mix…
▽ More
It has been a long-standing goal to bring massive objects into a superposition of different locations in real space, not only to confirm quantum theory in new regimes, but also to explore the interface with gravity. The main challenge is usually thought to arise from forces or scattering due to environmental fields and particles that decohere the large object's wave function into a statistical mixture. We unveil a decoherence channel which cannot be eliminated by improved isolation from the environment. It originates from sound waves within the object, which are excited as part of any splitting process and carry partial "Welcher Weg" information. This puts stringent constraints on future spatial superpositions of large objects.
△ Less
Submitted 27 September, 2024; v1 submitted 24 May, 2023;
originally announced May 2023.
-
Electron spin spectroscopy of single TEMPO dimers coupled via interfering tunneling currents
Authors:
Yishay Manassen,
Moamen Jbara,
Michael Averbukh,
Zion Hazan,
Carsten Henkel,
Baruch Horovitz
Abstract:
We report the detection of electron spin resonance (ESR) in individual dimers of the stable free radical 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO). ESR is measured by the current fluctuations in a scanning tunnelling microscope (ESR-STM method). The multi-peak power spectra, distinct from macroscopic data, are assigned to dimers having exchange and Dzyaloshinskii-Moriya interactions in presenc…
▽ More
We report the detection of electron spin resonance (ESR) in individual dimers of the stable free radical 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO). ESR is measured by the current fluctuations in a scanning tunnelling microscope (ESR-STM method). The multi-peak power spectra, distinct from macroscopic data, are assigned to dimers having exchange and Dzyaloshinskii-Moriya interactions in presence of spin-orbit coupling. These interactions are generated in our model by interfering electronic tunneling pathways from tip to sample via the dimer's two molecules. This is the first demonstration that tunneling via two spins is a valid mechanism of the ESR-STM method.
△ Less
Submitted 28 January, 2022;
originally announced January 2022.
-
Soft wetting with (a)symmetric Shuttleworth effect
Authors:
C. Henkel,
M. H. Essink,
Tuong Hoang,
G. J. van Zwieten,
E. H. van Brummelen,
U. Thiele,
J. H. Snoeijer
Abstract:
The wetting of soft polymer substrates brings in multiple complexities as compared to the wetting on rigid substrates. The contact angle of the liquid is no longer governed by Young's law, but is affected by the substrate's bulk and surface deformations. On top of that, elastic interfaces exhibit a surface energy that depends on how much they are stretched -- a feature known as the Shuttleworth ef…
▽ More
The wetting of soft polymer substrates brings in multiple complexities as compared to the wetting on rigid substrates. The contact angle of the liquid is no longer governed by Young's law, but is affected by the substrate's bulk and surface deformations. On top of that, elastic interfaces exhibit a surface energy that depends on how much they are stretched -- a feature known as the Shuttleworth effect (or as surface-elasticity). Here we present two models by which we explore the wetting of drops in the presence of a strong Shuttleworth effect. The first model is macroscopic in character and consistently accounts for large deformations via a neo-Hookean elasticity. The second model is based on a mesoscopic description of wetting, using a reduced description of the substrate's elasticity. While the second model is more empirical in terms of the elasticity, it enables a gradient dynamics formulation for soft wetting dynamics. We provide a detailed comparison between the equilibrium states predicted by the two models, from which we deduce robust features of soft wetting in the presence of a strong Shuttleworth effect. Specifically, we show that the (a)symmetry of the Shuttleworth effect between the "dry" and "wet" states governs horizontal deformations in the substrate. Our results are discussed in the light of recent experiments on the wettability of stretched substrates.
△ Less
Submitted 11 January, 2022;
originally announced January 2022.
-
Gradient-dynamics model for liquid drops on elastic substrates
Authors:
Christopher Henkel,
Jacco H. Snoeijer,
Uwe Thiele
Abstract:
The wetting of soft elastic substrates exhibits many features that have no counterpart on rigid surfaces. Modelling the detailed elastocapillary interactions is challenging, and has so far been limited to single contact lines or single drops. Here we propose a reduced long-wave model that captures the main qualitative features of statics and dynamics of soft wetting, but which can be applied to en…
▽ More
The wetting of soft elastic substrates exhibits many features that have no counterpart on rigid surfaces. Modelling the detailed elastocapillary interactions is challenging, and has so far been limited to single contact lines or single drops. Here we propose a reduced long-wave model that captures the main qualitative features of statics and dynamics of soft wetting, but which can be applied to ensembles of droplets. The model has the form of a gradient dynamics on an underlying free energy that reflects capillarity, wettability and compressional elasticity. With the model we first recover the double transition in the equilibrium contact angles that occurs when increasing substrate softness from ideally rigid towards very soft (i.e., liquid). Second, the spreading of single drops of partially and completely wetting liquids is considered showing that known dependencies of the dynamic contact angle on contact line velocity are well reproduced. Finally, we go beyond the single droplet picture and consider the coarsening for a two-drop system as well as for a large ensemble of drops. It is shown that the dominant coarsening mode changes with substrate softness in a nontrivial way.
△ Less
Submitted 18 July, 2021;
originally announced July 2021.
-
Realization of a complete Stern-Gerlach interferometer: Towards a test of quantum gravity
Authors:
Yair Margalit,
Or Dobkowski,
Zhifan Zhou,
Omer Amit,
Yonathan Japha,
Samuel Moukouri,
Daniel Rohrlich,
Anupam Mazumdar,
Sougato Bose,
Carsten Henkel,
Ron Folman
Abstract:
The Stern-Gerlach effect, discovered a century ago, has become a paradigm of quantum mechanics. Surprisingly there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. Specifically, no full-loop Stern-Gerlach interferometer has been realized with the scheme as envisioned decades ago. Furth…
▽ More
The Stern-Gerlach effect, discovered a century ago, has become a paradigm of quantum mechanics. Surprisingly there has been little evidence that the original scheme with freely propagating atoms exposed to gradients from macroscopic magnets is a fully coherent quantum process. Specifically, no full-loop Stern-Gerlach interferometer has been realized with the scheme as envisioned decades ago. Furthermore, several theoretical studies have explained why such an interferometer is a formidable challenge. Here we provide a detailed account of the first full-loop Stern-Gerlach interferometer realization, based on highly accurate magnetic fields, originating from an atom chip, that ensure coherent operation within strict constraints described by previous theoretical analyses. Achieving this high level of control over magnetic gradients is expected to facilitate technological as well as fundamental applications, such as probing the interface of quantum mechanics and gravity. While the experimental realization described here is for a single atom, future challenges would benefit from utilizing macroscopic objects doped with a single spin. Specifically, we show that such an experiment is in principle feasible, opening the door to a new era of fundamental probes.
△ Less
Submitted 21 November, 2020;
originally announced November 2020.
-
Vacuum-Induced Saturation in Plasmonic Nanoparticles
Authors:
Felix Stete,
Wouter Koopman,
Carsten Henkel,
Oliver Benson,
Günter Kewes,
Matias Bargheer
Abstract:
Vacuum fluctuations are a fundamental feature of quantized fields. It is usually assumed that observations connected to vacuum fluctuations require a system well isolated from other influences. In this work, we demonstrate that effects of the quantum vacuum can already occur in simple colloidal nano-assemblies prepared by wet chemistry. We claim that the electromagnetic field fluctuations at the z…
▽ More
Vacuum fluctuations are a fundamental feature of quantized fields. It is usually assumed that observations connected to vacuum fluctuations require a system well isolated from other influences. In this work, we demonstrate that effects of the quantum vacuum can already occur in simple colloidal nano-assemblies prepared by wet chemistry. We claim that the electromagnetic field fluctuations at the zero-point level saturate the absorption of dye molecules self-assembled at the surface of plasmonic nano-resonators. For this effect to occur, reaching the strong coupling regime between the plasmons and excitons is not required. This intriguing effect of vacuum-induced saturation (VISA) is discussed within a simple quantum optics picture and demonstrated by comparing the optical spectra of hybrid gold-core dye-shell nanorods to electromagnetic simulations.
△ Less
Submitted 21 August, 2020;
originally announced August 2020.
-
Remarks about surface plasmons and their stability
Authors:
Gino Wegner,
Carsten Henkel
Abstract:
We comment on the macroscopic model for surface plasmons of H.-Y. Deng [New J. Phys. 21 (2019) 043055; arXiv:1712.06101] and a claim, based on energy conversion from charges to the electric field, that surface plasmons on metallic surfaces may become unstable [J. Phys.: Cond. Matt. 29 (2017) 455002; arXiv:1606.06239, 1701.01060]. The discussion revolves around the formulation of charge conservatio…
▽ More
We comment on the macroscopic model for surface plasmons of H.-Y. Deng [New J. Phys. 21 (2019) 043055; arXiv:1712.06101] and a claim, based on energy conversion from charges to the electric field, that surface plasmons on metallic surfaces may become unstable [J. Phys.: Cond. Matt. 29 (2017) 455002; arXiv:1606.06239, 1701.01060]. The discussion revolves around the formulation of charge conservation in the bulk and the surface of a metal. We elaborate in particular on the role of a finite electric current normal to the surface. Using a scheme of Cercignani and Lampis and of Zaremba, we point out that the model chosen by Deng for the non-specular scattering of electrons needs to be amended to prevent the disappearance of charges at the surface. Different models and approaches in the literature on surface plasmons are reviewed: the interfacial excess field approach of Bedeaux and Vlieger which contains Deng's macroscopic model, the assumption of specular reflection of Ritchie and Marusak, a hydrodynamic model with a composite charge density (partially localized at the surface), the local dielectric model, and a macroscopic method with (anti)symmetric fictitious stimuli (used, e.g., by García-Moliner and Flores). This puts Deng's results into perspective and illustrates problems with his approach.
△ Less
Submitted 7 May, 2020;
originally announced May 2020.
-
Solving an old puzzle: fine structure of diffraction spots from an azo-polymer surface relief grating
Authors:
Joachim Jelken,
Carsten Henkel,
Svetlana Santer
Abstract:
We report on the experimental and theoretical interpretation of the diffraction of a probe beam during inscription of a surface relief grating with an interference pattern into a photo-responsive polymer film. For this we developed a set-up allowing for the simultaneous recording of the diffraction efficiency (DE), the fine structure of the diffraction spot and the topographical changes, in situ a…
▽ More
We report on the experimental and theoretical interpretation of the diffraction of a probe beam during inscription of a surface relief grating with an interference pattern into a photo-responsive polymer film. For this we developed a set-up allowing for the simultaneous recording of the diffraction efficiency (DE), the fine structure of the diffraction spot and the topographical changes, in situ and in real time while the film is irradiated. The time dependence of the DE, as the surface relief deepens, follows a Bessel function exhibiting maxima and minima. The size of the probe beam relative to the inscribed grating (i.e., to the size of the writing beams) matters and has to be considered for the interpretation of the DE signal. It is also at the origin of a fine structure within the diffraction spot where ring-shaped features appear once an irradiation time corresponding to the first maximum of the DE has been exceeded.
△ Less
Submitted 21 October, 2019;
originally announced October 2019.
-
Testing the weak equivalence principle by differential measurements of fundamental constants in the Magellanic Clouds
Authors:
S. A. Levshakov,
K. -W. Ng,
C. Henkel,
B. Mookerjea,
I. I. Agafonova,
S. -Y. Liu,
W. -H. Wang
Abstract:
Non-standard fields are assumed to be responsible for phenomena attributed to dark energy and dark matter. Being coupled to ordinary matter, these fields modify the masses and/or charges of the elementary particles, thereby violating the Weak Equivalence Principle. Thus, values of fundamental constants such as the proton-to-electron mass ratio, mu, and/or the fine structure constant, alpha, measur…
▽ More
Non-standard fields are assumed to be responsible for phenomena attributed to dark energy and dark matter. Being coupled to ordinary matter, these fields modify the masses and/or charges of the elementary particles, thereby violating the Weak Equivalence Principle. Thus, values of fundamental constants such as the proton-to-electron mass ratio, mu, and/or the fine structure constant, alpha, measured in different environment conditions can be used as probes for this coupling. Here we perform differential measurements of F = mu*alpha^2 to test a non-standard coupling in the Magellanic Clouds - dwarf galaxies where the overall mass budget is dominated by dark matter. The analysis is based on [CI] and CO lines observed with the Herschel Space Observatory. Since these lines have different sensitivities to changes in mu and alpha, the combined alpha and mu variations can be evaluated through the radial velocity offsets, Delta V, between the CO and [CI] lines. Averaging over nine positions in the Magellanic Clouds, we obtain <Delta V> = -0.02+/-0.07 km/s, leading to |Delta F/F| < 2*10^-7 (1sigma), where Delta F/F = (F_obs-F_lab)/F_lab}. However, for one position observed with five times higher spectral resolution we find Delta V = -0.05+/-0.02 km/s, resulting in Delta F/F = (-1.7+/-0.7)*10^-7. Whether this offset is due to changes in the fundamental constants, due to chemical segregation in the emitting gas or merely due to Doppler noise requires further investigations.
△ Less
Submitted 9 June, 2019;
originally announced June 2019.
-
Stern-Gerlach splitting of low-energy ion beams
Authors:
Carsten Henkel,
Georg Jacob,
Felix Stopp,
Ferdinand Schmidt-Kaler,
Mark Keil,
Yonathan Japha,
Ron Folman
Abstract:
We present a feasibility study with several magnetic field configurations for creating spin-dependent forces that can split a low-energy ion beam by the Stern-Gerlach effect. To the best of our knowledge, coherent spin-splittings of charged particles have yet to be realised. Our proposal is based on ion source parameters taken from a recent experiment that demonstrated single-ion implantation from…
▽ More
We present a feasibility study with several magnetic field configurations for creating spin-dependent forces that can split a low-energy ion beam by the Stern-Gerlach effect. To the best of our knowledge, coherent spin-splittings of charged particles have yet to be realised. Our proposal is based on ion source parameters taken from a recent experiment that demonstrated single-ion implantation from a high-brightness ion source combined with a radio-frequency Paul trap. The inhomogeneous magnetic fields can be created by permanently magnetised microstructures or from current-carrying wires with sizes in the micron range, such as those recently used in a successful implementation of the Stern-Gerlach effect with neutral atoms. All relevant forces (Lorentz force and image charges) are taken into account, and measurable splittings are found by analytical and numerical calculations.
△ Less
Submitted 10 April, 2019; v1 submitted 10 March, 2019;
originally announced March 2019.
-
Nano-scale thermal transfer -- an invitation to fluctuation electrodynamics
Authors:
Carsten Henkel
Abstract:
An electromagnetic theory of thermal radiation is outlined, based on the fluctuation electrodynamics of Rytov and co-workers. We discuss the basic concepts and the status of different approximations. The physical content is illustrated with a few examples on near-field heat transfer.
An electromagnetic theory of thermal radiation is outlined, based on the fluctuation electrodynamics of Rytov and co-workers. We discuss the basic concepts and the status of different approximations. The physical content is illustrated with a few examples on near-field heat transfer.
△ Less
Submitted 27 September, 2016;
originally announced September 2016.
-
Electric-Field Noise above a Thin Dielectric Layer on Metal Electrodes
Authors:
Muir Kumph,
Carsten Henkel,
Peter Rabl,
Michael Brownnutt,
Rainer Blatt
Abstract:
The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare…
▽ More
The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electric-field noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these findings are of particular importance for the understanding and mitigation of unwanted heating and decoherence in miniaturized ion traps.
△ Less
Submitted 2 November, 2015;
originally announced November 2015.
-
"Fully covariant radiation force on a polarizable particle" - Reply to the Comment by Volokitin and Persson
Authors:
Carsten Henkel,
Gregor Pieplow
Abstract:
We argue that the theories of Volokitin and Persson [Comment arXiv:1405:2525], of Dedkov and Kyasov [J. Phys.: Condens. Matter 20 (2008) 354006], and Pieplow and Henkel [New J. Phys. 15 (2013) 023027] agree on the electromagnetic force on a small, polarizable particle that is moving parallel to a planar, macroscopic body, as far as the contribution of evanescent waves is concerned. The apparent di…
▽ More
We argue that the theories of Volokitin and Persson [Comment arXiv:1405:2525], of Dedkov and Kyasov [J. Phys.: Condens. Matter 20 (2008) 354006], and Pieplow and Henkel [New J. Phys. 15 (2013) 023027] agree on the electromagnetic force on a small, polarizable particle that is moving parallel to a planar, macroscopic body, as far as the contribution of evanescent waves is concerned. The apparent differences are discussed in detail and explained by choices of units and integral transformations. We point out in particular the role of Lorentz contraction in the procedure used by Volokitin and Persson, where a macroscopic body is "diluted" to get the force on a small particle. Differences that appear in the contribution of propagating photons are briefly mentioned.
△ Less
Submitted 19 July, 2014;
originally announced July 2014.
-
Strong tip-sample coupling in thermal radiation scanning tunneling microscopy
Authors:
Karl Joulain,
Philippe Ben-Abdallah,
Pierre-Olivier Chapuis,
Yannick De Wilde,
Arthur Babuty,
Carsten Henkel
Abstract:
We analyze how a probing particle modifies the infrared electromagnetic near field of a sample. The particle, described by electric and magnetic polarizabilities, represents the tip of an apertureless scanning optical near-field microscope (SNOM). We show that the interaction with the sample can be accounted for by ascribing to the particle dressed polarizabilities that combine the effects of imag…
▽ More
We analyze how a probing particle modifies the infrared electromagnetic near field of a sample. The particle, described by electric and magnetic polarizabilities, represents the tip of an apertureless scanning optical near-field microscope (SNOM). We show that the interaction with the sample can be accounted for by ascribing to the particle dressed polarizabilities that combine the effects of image dipoles with retardation. When calculated from these polarizabilities, the SNOM signal depends only on the fields without the perturbing tip. If the studied surface is not illuminated by an external source but heated instead, the signal is closely related to the projected electromagnetic local density of states (EM-LDOS). Our calculations provide the link between the measured far-field spectra and the sample's optical properties.We also analyze the case where the probing particle is hotter than the sample and evaluate the impact of the dressed polarizabilities on near-field radiative heat transfer. We show that such a heated probe above a surface performs a surface spectroscopy, in the sense that the spectrum of the heat current is closely related to the local electromagnetic density of states. The calculations agree well with available experimental data.
△ Less
Submitted 8 November, 2013;
originally announced November 2013.
-
A search for varying fundamental constants using Hz-level frequency measurements of cold CH molecules
Authors:
S. Truppe,
R. J. Hendricks,
S. K. Tokunaga,
H. J. Lewandowski,
M. G. Kozlov,
Christian Henkel,
E. A. Hinds,
M. R. Tarbutt
Abstract:
Many modern theories predict that the fundamental constants depend on time, position, or the local density of matter. We develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that…
▽ More
Many modern theories predict that the fundamental constants depend on time, position, or the local density of matter. We develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high and low density environments of the Earth and the interstellar medium. For the fine structure constant we find Δα/α= (0.3 +/- 1.1)*10^{-7}, the strongest limit to date on such a variation of α. For the electron-to-proton mass ratio we find Δμ/μ= (-0.7 +/- 2.2) * 10^{-7}. We suggest how dedicated astrophysical measurements can improve these constraints further and can also constrain temporal variation of the constants.
△ Less
Submitted 7 August, 2013;
originally announced August 2013.
-
Heat superdiffusion in plasmonic nanostructure networks
Authors:
Philippe Ben-Abdallah,
Riccardo Messina,
Svend-Age Biehs,
Maria Tschikin,
Karl Joulain,
Carsten Henkel
Abstract:
Heat-transport mechanism mediated by near-field interactions in plasmonic nanostructures networks is shown to be analogous to a generalized random-walk process. Existence of superdiffusive regimes is demonstrated both in linear ordered chains and in three dimensional random networks by analyzing the asymptotic behavior of the corresponding probability distribution function. We show that the spread…
▽ More
Heat-transport mechanism mediated by near-field interactions in plasmonic nanostructures networks is shown to be analogous to a generalized random-walk process. Existence of superdiffusive regimes is demonstrated both in linear ordered chains and in three dimensional random networks by analyzing the asymptotic behavior of the corresponding probability distribution function. We show that the spread of heat in these networks is described by a type of Lévy flight. The presence of such anomalous heat transport regimes in plasmonic networks opens the way to the design of a new generation of composite materials able to transport heat faster than the normal diffusion process in solids.
△ Less
Submitted 20 June, 2013;
originally announced June 2013.
-
Pathway to the Square Kilometre Array - The German White Paper -
Authors:
F. Aharonian,
T. G. Arshakian,
B. Allen,
R. Banerjee,
R. Beck,
W. Becker,
D. J. Bomans,
D. Breitschwerdt,
M. Brüggen,
A. Brunthaler,
B. Catinella,
D. Champion,
B. Ciardi,
R. Crocker,
M. A. de Avillez,
R. J. Dettmar,
D. Engels,
T. Enßlin,
H. Enke,
T. Fieseler,
L. Gizon,
E. Hackmann,
B. Hartmann,
C. Henkel,
M. Hoeft
, et al. (48 additional authors not shown)
Abstract:
The Square Kilometre Array (SKA) is the most ambitious radio telescope ever planned. With a collecting area of about a square kilometre, the SKA will be far superior in sensitivity and observing speed to all current radio facilities. The scientific capability promised by the SKA and its technological challenges provide an ideal base for interdisciplinary research, technology transfer, and collabor…
▽ More
The Square Kilometre Array (SKA) is the most ambitious radio telescope ever planned. With a collecting area of about a square kilometre, the SKA will be far superior in sensitivity and observing speed to all current radio facilities. The scientific capability promised by the SKA and its technological challenges provide an ideal base for interdisciplinary research, technology transfer, and collaboration between universities, research centres and industry. The SKA in the radio regime and the European Extreme Large Telescope (E-ELT) in the optical band are on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI) and have been recognised as the essential facilities for European research in astronomy.
This "White Paper" outlines the German science and R&D interests in the SKA project and will provide the basis for future funding applications to secure German involvement in the Square Kilometre Array.
△ Less
Submitted 16 January, 2013;
originally announced January 2013.
-
Fully covariant radiation force on a polarizable particle
Authors:
Gregor Pieplow,
Carsten Henkel
Abstract:
The electromagnetic force on a polarizable particle is calculated in a covariant framework. Local equilibrium temperatures for the electromagnetic field and the particle's dipole moment are assumed, using a relativistic formulation of the fluctuation-dissipation theorem. Two examples illustrate radiative friction forces: a particle moving through a homogeneous radiation background and above a plan…
▽ More
The electromagnetic force on a polarizable particle is calculated in a covariant framework. Local equilibrium temperatures for the electromagnetic field and the particle's dipole moment are assumed, using a relativistic formulation of the fluctuation-dissipation theorem. Two examples illustrate radiative friction forces: a particle moving through a homogeneous radiation background and above a planar interface. Previous results for arbitrary relative velocities are recovered in a compact way.
△ Less
Submitted 28 September, 2012;
originally announced September 2012.
-
Van der Waals-Casimir-Polder interaction of an atom with a composite surface
Authors:
Elad Eizner,
Baruch Horovitz,
Carsten Henkel
Abstract:
We study the dispersion interaction of the van der Waals and Casimir-Polder (vdW-CP) type between a neutral atom and the surface of a metal by allowing for nonlocal electrodynamics, i.e. electron diffusion. We consider two models: (i) bulk diffusion, and (ii) diffusion in a surface charge layer. In both cases the transition to a semiconductor is continuous as a function of the conductivity, unlike…
▽ More
We study the dispersion interaction of the van der Waals and Casimir-Polder (vdW-CP) type between a neutral atom and the surface of a metal by allowing for nonlocal electrodynamics, i.e. electron diffusion. We consider two models: (i) bulk diffusion, and (ii) diffusion in a surface charge layer. In both cases the transition to a semiconductor is continuous as a function of the conductivity, unlike the case of a local model. The relevant parameter is the electric screening length and depends on the carrier diffusion constant. We find that for distances comparable to the screening length, vdW-CP data can distinguish between bulk and surface diffusion, hence it can be a sensitive probe for surface states.
△ Less
Submitted 29 June, 2012; v1 submitted 7 May, 2012;
originally announced May 2012.
-
Surface plasmons at composite surfaces with diffusive charges
Authors:
Baruch Horovitz,
Carsten Henkel
Abstract:
Metal surfaces with disorder or with nanostructure modifications are studied, allowing for a localized charge layer (CL) in addition to continuous charges (CC) in the bulk, both charges having a compressional or diffusive non-local response. The notorious problem of "additional boundary conditions" is resolved with the help of a Boltzmann equation that involves the scattering between the two charg…
▽ More
Metal surfaces with disorder or with nanostructure modifications are studied, allowing for a localized charge layer (CL) in addition to continuous charges (CC) in the bulk, both charges having a compressional or diffusive non-local response. The notorious problem of "additional boundary conditions" is resolved with the help of a Boltzmann equation that involves the scattering between the two charge types. Depending on the strength of this scattering, the oscillating charges can be dominantly CC or CL; the surface plasmon (SP) resonance acquires then a relatively small linewidth, in agreement with a large set of data. With a few parameters our model describes a large variety of SP dispersions corresponding to observed data.
△ Less
Submitted 17 September, 2011;
originally announced September 2011.
-
Effects of spatial dispersion in near-field radiative heat transfer between two parallel metallic surfaces
Authors:
Pierre-Olivier Chapuis,
Sebastian Volz,
Carsten Henkel,
Karl Joulain,
Jean-Jacques Greffet
Abstract:
We study the heat transfer between two parallel metallic semi-infinite media with a gap in the nanometer-scale range. We show that the near-field radiative heat flux saturates at distances smaller than the metal skin depth when using a local dielectric constant and investigate the origin of this effect. The effect of non-local corrections is analysed using the Lindhard-Mermin and Boltzmann-Mermi…
▽ More
We study the heat transfer between two parallel metallic semi-infinite media with a gap in the nanometer-scale range. We show that the near-field radiative heat flux saturates at distances smaller than the metal skin depth when using a local dielectric constant and investigate the origin of this effect. The effect of non-local corrections is analysed using the Lindhard-Mermin and Boltzmann-Mermin models. We find that local and non-local models yield the same heat fluxes for gaps larger than 2 nm. Finally, we explain the saturation observed in a recent experiment as a manifestation of the skin depth and show that heat is mainly dissipated by eddy currents in metallic bodies.
△ Less
Submitted 13 February, 2008;
originally announced February 2008.
-
Magnetic noise around metallic microstructures
Authors:
Bo Zhang,
Carsten Henkel
Abstract:
We compute the local spectrum of the magnetic field near a metallic microstructure at finite temperature. Our main focus is on deviations from a plane-layered geometry for which we review the main properties. Arbitrary geometries are handled with the help of numerical calculations based on surface integral equations. The magnetic noise shows a significant polarization anisotropy above flat wires…
▽ More
We compute the local spectrum of the magnetic field near a metallic microstructure at finite temperature. Our main focus is on deviations from a plane-layered geometry for which we review the main properties. Arbitrary geometries are handled with the help of numerical calculations based on surface integral equations. The magnetic noise shows a significant polarization anisotropy above flat wires with finite lateral width, in stark contrast to an infinitely wide wire. Within the limits of a two-dimensional setting, our results provide accurate estimates for loss and dephasing rates in so-called `atom chip traps' based on metallic wires. A simple approximation based on the incoherent summation of local current elements gives qualitative agreement with the numerics, but fails to describe current correlations among neighboring objects.
△ Less
Submitted 10 September, 2007; v1 submitted 5 June, 2007;
originally announced June 2007.
-
Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror
Authors:
Helene Perrin,
Yves Colombe,
Brigitte Mercier,
Vincent Lorent,
Carsten Henkel
Abstract:
We present experimental results showing the diffuse reflection of a Bose-Einstein condensate from a rough mirror, consisting of a dielectric substrate supporting a blue-detuned evanescent wave. The scattering is anisotropic, more pronounced in the direction of the surface propagation of the evanescent wave. These results agree very well with theoretical predictions.
We present experimental results showing the diffuse reflection of a Bose-Einstein condensate from a rough mirror, consisting of a dielectric substrate supporting a blue-detuned evanescent wave. The scattering is anisotropic, more pronounced in the direction of the surface propagation of the evanescent wave. These results agree very well with theoretical predictions.
△ Less
Submitted 5 September, 2006; v1 submitted 11 May, 2006;
originally announced May 2006.
-
Electromagnetic field correlations near a surface with a nonlocal optical response
Authors:
Carsten Henkel,
Karl Joulain
Abstract:
The coherence length of the thermal electromagnetic field near a planar surface has a minimum value related to the nonlocal dielectric response of the material. We perform two model calculations of the electric energy density and the field's degree of spatial coherence. Above a polar crystal, the lattice constant gives the minimum coherence length. It also gives the upper limit to the near field…
▽ More
The coherence length of the thermal electromagnetic field near a planar surface has a minimum value related to the nonlocal dielectric response of the material. We perform two model calculations of the electric energy density and the field's degree of spatial coherence. Above a polar crystal, the lattice constant gives the minimum coherence length. It also gives the upper limit to the near field energy density, cutting off its $1/z^3$ divergence. Near an electron plasma described by the semiclassical Lindhard dielectric function, the corresponding length scale is fixed by plasma screening to the Thomas-Fermi length. The electron mean free path, however, sets a larger scale where significant deviations from the local description are visible.
△ Less
Submitted 23 March, 2006;
originally announced March 2006.
-
Optical microscopy via spectral modifications of a nano-antenna
Authors:
T. Kalkbrenner,
U. Hakanson,
A. Schädle,
S. Burger,
C. Henkel,
V. Sandoghdar
Abstract:
The existing optical microscopes form an image by collecting photons emitted from an object. Here we report on the experimental realization of microscopy without the need for direct optical communication with the sample. To achieve this, we have scanned a single gold nanoparticle acting as a nano-antenna in the near field of a sample and have studied the modification of its intrinsic radiative p…
▽ More
The existing optical microscopes form an image by collecting photons emitted from an object. Here we report on the experimental realization of microscopy without the need for direct optical communication with the sample. To achieve this, we have scanned a single gold nanoparticle acting as a nano-antenna in the near field of a sample and have studied the modification of its intrinsic radiative properties by monitoring its plasmon spectrum.
△ Less
Submitted 26 September, 2005;
originally announced September 2005.
-
Radiative Transfer and Atom Transport
Authors:
Carsten Henkel
Abstract:
The report deals with classical and quantum descriptions of particles that interact with smooth random potentials, for example ultracold atoms in the dipole potential of an optical speckle pattern. In addition, a discussion of the link between Radiative Transfer theory and the underlying coherence theory of wave optics is presented. The Radiative Transfer Equation is shown to emerge as a limitin…
▽ More
The report deals with classical and quantum descriptions of particles that interact with smooth random potentials, for example ultracold atoms in the dipole potential of an optical speckle pattern. In addition, a discussion of the link between Radiative Transfer theory and the underlying coherence theory of wave optics is presented. The Radiative Transfer Equation is shown to emerge as a limiting case of the Bethe-Salpeter Equation, and some next-order corrections are discussed.
△ Less
Submitted 3 May, 2005;
originally announced May 2005.
-
The Physics of Atom-Surface Interactions
Authors:
Carsten Henkel
Abstract:
A tutorial overview is given on interactions between atoms and surfaces that are mediated by the electromagnetic field. The emphasis is on dispersion (or van der Waals) forces and transitions induced by thermal fluctuations in the near field of a surface. Applications with cold atoms held in microscopic traps near surfaces ("atom chips") provide the experimental background for this theory lectur…
▽ More
A tutorial overview is given on interactions between atoms and surfaces that are mediated by the electromagnetic field. The emphasis is on dispersion (or van der Waals) forces and transitions induced by thermal fluctuations in the near field of a surface. Applications with cold atoms held in microscopic traps near surfaces ("atom chips") provide the experimental background for this theory lecture. We do not cover the chemical physics aspects that are relevant at distances comparable to the atomic scale, like adsorption and diffusion on surfaces, growth of nanostructures, or atomic beam diffraction from crystalline surfaces. These are covered by other lecturers.
△ Less
Submitted 19 May, 2004; v1 submitted 17 May, 2004;
originally announced May 2004.
-
Coupled surface polaritons and the Casimir force
Authors:
Carsten Henkel,
Karl Joulain,
Jean-Philippe Mulet,
Jean-Jacques Greffet
Abstract:
The Casimir force between metallic plates made of realistic materials is evaluated for distances in the nanometer range. A spectrum over real frequencies is introduced and shows narrow peaks due to surface resonances (plasmon polaritons or phonon polaritons) that are coupled across the vacuum gap. We demonstrate that the Casimir force originates from the attraction (repulsion) due to the corresp…
▽ More
The Casimir force between metallic plates made of realistic materials is evaluated for distances in the nanometer range. A spectrum over real frequencies is introduced and shows narrow peaks due to surface resonances (plasmon polaritons or phonon polaritons) that are coupled across the vacuum gap. We demonstrate that the Casimir force originates from the attraction (repulsion) due to the corresponding symmetric (antisymmetric) eigenmodes, respectively. This picture is used to derive a simple analytical estimate of the Casimir force at short distances. We recover the result known for Drude metals without absorption and compute the correction for weakly absorbing materials.
△ Less
Submitted 7 November, 2003; v1 submitted 26 August, 2003;
originally announced August 2003.
-
Coherent Transport
Authors:
C. Henkel
Abstract:
We discuss the transport of matter waves in low-dimensional waveguides. Due to scattering from uncontrollable noise fields, the spatial coherence gets reduced and eventually lost. We develop a description of this decoherence process in terms of transport equations for the atomic Wigner function. We outline its derivation and discuss the special case of white noise where an analytical solution ca…
▽ More
We discuss the transport of matter waves in low-dimensional waveguides. Due to scattering from uncontrollable noise fields, the spatial coherence gets reduced and eventually lost. We develop a description of this decoherence process in terms of transport equations for the atomic Wigner function. We outline its derivation and discuss the special case of white noise where an analytical solution can be found.
△ Less
Submitted 18 April, 2001; v1 submitted 5 December, 2000;
originally announced December 2000.
-
Spatial coherence of thermal near fields
Authors:
C. Henkel,
K. Joulain,
R. Carminati,
J. -J. Greffet
Abstract:
We analyze the spatial coherence of the electromagnetic field emitted by a half-space at temperature T close to the interface. An asymptotic analysis allows to identify three different contributions to the cross-spectral density tensor in the near-field regime. It is shown that the coherence length can be either much larger or much shorter than the wavelength depending on the dominant contributi…
▽ More
We analyze the spatial coherence of the electromagnetic field emitted by a half-space at temperature T close to the interface. An asymptotic analysis allows to identify three different contributions to the cross-spectral density tensor in the near-field regime. It is shown that the coherence length can be either much larger or much shorter than the wavelength depending on the dominant contribution.
△ Less
Submitted 10 August, 2000;
originally announced August 2000.
-
Single-molecule spectroscopy near structured dielectrics
Authors:
Carsten Henkel,
Vahid Sandoghdar
Abstract:
We present an analytical approach to the calculation of the linewidth and lineshift of an atom or molecule in the near field of a structured dielectric surface. For soft surface corrugations with amplitude lambda/50, we find variations of the linewidth in the ten percent region. More strikingly, the shift of the molecular resonance can reach several natural linewidths. We demonstrate that the la…
▽ More
We present an analytical approach to the calculation of the linewidth and lineshift of an atom or molecule in the near field of a structured dielectric surface. For soft surface corrugations with amplitude lambda/50, we find variations of the linewidth in the ten percent region. More strikingly, the shift of the molecular resonance can reach several natural linewidths. We demonstrate that the lateral resolution is of the order of the molecule-surface distance. We give a semiquantitative explanation of the outcome of our calculations that is based on simple intuitive models.
△ Less
Submitted 6 October, 1998;
originally announced October 1998.