Dag Winkler - Profile on Academia.edu (original) (raw)
Papers by Dag Winkler
Applied Physics Letters, 2020
The transport properties of a YBa2Cu3O7−δ superconducting quantum interference device (SQUID) bas... more The transport properties of a YBa2Cu3O7−δ superconducting quantum interference device (SQUID) based on grooved Dayem bridge weak links are studied as a function of temperature: at high temperatures (60 K<T<Tc=89 K), the weak links show properties similar to superconductor–normal conductor–superconductor junctions, while at temperatures below 60 K, the weak links behave like short Dayem bridges. Using these devices, we have fabricated SQUID magnetometers with galvanically coupled in-plane pickup loops: at T = 77 K, magnetic field white noise levels as low as 63 fT/Hz have been achieved.
Nanomaterials, 2018
We developed a novel biodetection method for influenza virus based on AC magnetic susceptibility ... more We developed a novel biodetection method for influenza virus based on AC magnetic susceptibility measurement techniques (the DynoMag induction technique) together with functionalized multi-core magnetic nanoparticles. The sample consisting of an incubated mixture of magnetic nanoparticles and rolling circle amplified DNA coils is injected into a tube by a peristaltic pump. The sample is moved as a plug to the two well-balanced detection coils and the dynamic magnetic moment in each position is read over a range of excitation frequencies. The time for making a complete frequency sweep over the relaxation peak is about 5 minutes (10 Hz–10 kHz with 20 data points). The obtained standard deviation of the magnetic signal at the relaxation frequency (around 100 Hz) is equal to about 10−5 (volume susceptibility SI units), which is in the same range obtained with the DynoMag system. The limit of detection with this method is found to be in the range of 1 pM.
Physica C: Superconductivity and its Applications, 2002
given and 72 posters were presented. The book of abstracts and the program venue were published a... more given and 72 posters were presented. The book of abstracts and the program venue were published at the web-site: www.squid2001.org. The book has the complete collection of abstracts (about 124). In this special volume of Physica C, 63 papers from the conference are published. Many people have contributed in creating the SQUID 2001 conference. Harold Weinstock at AFOSR and Horst Rogalla at Twente University (representing ESAS) suggested, initiated and promoted the event. Hans Koch, John Clarke and Tord Claeson gave important input to the conference venue. The chairmen of the different sessions put in a lot of work in organizing balanced and interesting sessions. We are especially indebted to John Clarke for an excellent summary of the scientific contributions and an outlook for the future. Per Magnelind and Alexander Tzalenchuk were responsible for the book of abstracts. Alexander's efficiency and competence made it possible to meet the deadline for submitting this collection of refereed articles to Physica C. Many more people at Chalmers and IMEGO helped out in various ways and the conference would not have succeeded without them.
Physica C: Superconductivity, 2006
The roadmap gives an overview on status and future developments in Superconducting Digital Electr... more The roadmap gives an overview on status and future developments in Superconducting Digital Electronics (SDE). Key areas in SDE under focus are applications, circuit simulation and design, circuit fabrication, interfacing and testing, cooling and system aspects, and new devices and materials. Care was taken to establish the vital link between research and development on the one hand and the industrial view on the other hand. The present roadmap is based on extensive input from the roadmap working group on SDE established by SCENET-the European Network for Superconductivity, intensified by the activities of the FLUXONICS Network-the European Foundry for Superconducting Electronics. It is the result of many years of discussion in the group and of consultations with experts in the field, on the way to bring together industrial expectations and visionary extrapolation and current status of technology.
Nanomaterials
The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO), hosts a quasi-tw... more The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO), hosts a quasi-two-dimensional electron gas (q2DEG), two-dimensional superconductivity, ferromagnetism, and giant Rashba spin-orbit coupling. The co-existence of two-dimensional superconductivity with gate-tunable spin-orbit coupling and multiband occupation is of particular interest for the realization of unconventional superconducting pairing. To investigate the symmetry of the superconducting order parameter, phase sensitive measurements of the Josephson effect are required. We describe an approach for the fabrication of artificial superconducting weak links at the LAO/STO interface using direct high-resolution electron beam lithography and low-energy argon ion beam irradiation. The method does not require lift-off steps or sacrificial layers. Therefore, resolution is only limited by the electron beam lithography and pattern transfer. We have realized superconducting weak links with a barrier thicknes...
On-scalp MEG sensor localization using magnetic dipole-like coils: A method for highly accurate co-registration
NeuroImage
Biosensors
The specific binding of oligonucleotide-tagged 100 nm magnetic nanoparticles (MNPs) to rolling ci... more The specific binding of oligonucleotide-tagged 100 nm magnetic nanoparticles (MNPs) to rolling circle products (RCPs) is investigated using our newly developed differential homogenous magnetic assay (DHMA). The DHMA measures ac magnetic susceptibility from a test and a control samples simultaneously and eliminates magnetic background signal. Therefore, the DHMA can reveal details of binding kinetics of magnetic nanoparticles at very low concentrations of RCPs. From the analysis of the imaginary part of the DHMA signal, we find that smaller MNPs in the particle ensemble bind first to the RCPs. When the RCP concentration increases, we observe the formation of agglomerates, which leads to lower number of MNPs per RCP at higher concentrations of RCPs. The results thus indicate that a full frequency range of ac susceptibility observation is necessary to detect low concentrations of target RCPs and a long amplification time is not required as it does not significantly increase the number ...
Source modelling in magnetoencephalography (MEG) requires precise co-registration of the sensor a... more Source modelling in magnetoencephalography (MEG) requires precise co-registration of the sensor array and the anatomical structure of the measured individual’s head. In conventional MEG, positions and orientations of the sensors relative to each other are fixed and known beforehand, requiring only localization of the head relative to the sensor array. Since the sensors in on-scalp MEG are positioned on the scalp, locations of the individual sensors depend on the subject’s head shape and size. The positions and orientations of on-scalp sensors must therefore be measured at every recording. This can be achieved by inverting conventional head localization, localizing the sensors relative to the head - rather than the other way around.In this study we present a practical method for localizing sensors using magnetic dipole-like coils attached to the subject’s head. We implement and evaluate the method in a set of on-scalp MEG recordings using a 7-channel on-scalp MEG system based on high...
Physica B+C
Superconducting aluminium tunnel junctions, operating in the quasi-particle regime, have been use... more Superconducting aluminium tunnel junctions, operating in the quasi-particle regime, have been used to probe the behaviour of an SIS mixer at photon energies approaching the superconducting gap energy. Comparisons with the performance calculated from the quantum theory of mixing give a very good agreement for a relatively high resistance array of AI junctions.
![Research paper thumbnail of Erratum: Static and dynamic properties of stacked Josephson junctions: Analytic solution [Phys. Rev. B56, 9106 (1997)]](https://attachments.academia-assets.com/69971010/thumbnails/1.jpg)
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Physical Review B
We study numerically and analytically the shape of a single fluxon moving in a double stacked Jos... more We study numerically and analytically the shape of a single fluxon moving in a double stacked Josephson junctions (SJJ's) for various junction parameters. We show that the fluxon in a double SJJ's consists of two components, which are characterized by different Swihart velocities and Josephson penetration depths. The weight coefficients of the two components depend on the parameters of the junctions and the velocity of the fluxon. It is shown that the fluxon in SJJ's may have an unusual shape with an inverted magnetic field in the second junction when the velocity of the fluxon is approaching the lower Swihart velocity. Finally, we study the influence of fluxon shape on flux-flow current-voltage characteristics and analyze the spectrum of Cherenkov radiation for fluxon velocity above the lower Swihart velocity. Analytic expression for the wavelength of Cherenkov radiation is derived.
Physical Review B
Static and dynamic properties of stacked Josephson junctions are studied theoretically. An approx... more Static and dynamic properties of stacked Josephson junctions are studied theoretically. An approximate analytic solution for a stack with arbitrary junction parameters was obtained. The analytic solution is in good agreement with numerical simulations. Characteristic penetration depths, Swihart velocities, the lower critical field, the first integral, and the free energy for a stack of nonidentical junctions were derived and studied for different parameters of the stack. We show that attractive interaction of fluxons in adjacent junctions exists in the dynamic state of the stack, leading to appearance of the ''in-phase'' state with fluxons on top of each other. In a given external magnetic field the Gibbs free energy has a number of local minima corresponding to particular fluxon distributions ͑modes͒ in the stack each representing a quasiequilibrium state. For a stack of N junctions each mode would result in N distinct flux-flow branches in the current-voltage characteristic. Taking into account that different modes with equal total number of fluxons are not identical we conclude that the total possible number of flux-flow branches can be much larger than the number of junctions in the stack.
YBaCuO hot-electron bolometer mixer
Physica C, 2000
ABSTRACT
High Voltage Induction Device
Interlayer Coupling and Superconducting Critical Temperature of Bi2Sr1.5La0.5CuO6+δ and Bi2Sr2CaCu2O8+δ: Incommensurate Effects of Pressure
Phys Rev Lett, 1999
... T. Murayama and Y. Ando Electrical Physics Department, Central Research Institute of Electric... more ... T. Murayama and Y. Ando Electrical Physics Department, Central Research Institute of Electric Power Industry, 2-11-1 Iwato-kita, Komae, Tokyo 201 ... This discrep-ancy has also been acknowledged by Anderson [4]. Up to now, the Tl-2201 compound is, however, the only excep ...
Weak links and dc SQUIDS on artificial nonsymmetric grain boundaries in YBa2Cu3O7-d
We have studied weak links and dc--SQUIDs made from pulsed laser deposited YBaâCuâO{sub 7-δ} thi... more We have studied weak links and dc--SQUIDs made from pulsed laser deposited YBaâCuâO{sub 7-δ} thin films on Y--ZrOâ bicrystal substrates. The transport properties of the weak links were studied as a function of the misorientation angle (θ) between the two halves of the bicrystal and an exponential dependence of the weak link critical current density was observed for angles up
Development of an electrowetting-based microfluidic platform for magnetic immunoassays
Micro cooling of squid sensor
Applied Physics Letters, 2020
The transport properties of a YBa2Cu3O7−δ superconducting quantum interference device (SQUID) bas... more The transport properties of a YBa2Cu3O7−δ superconducting quantum interference device (SQUID) based on grooved Dayem bridge weak links are studied as a function of temperature: at high temperatures (60 K<T<Tc=89 K), the weak links show properties similar to superconductor–normal conductor–superconductor junctions, while at temperatures below 60 K, the weak links behave like short Dayem bridges. Using these devices, we have fabricated SQUID magnetometers with galvanically coupled in-plane pickup loops: at T = 77 K, magnetic field white noise levels as low as 63 fT/Hz have been achieved.
Nanomaterials, 2018
We developed a novel biodetection method for influenza virus based on AC magnetic susceptibility ... more We developed a novel biodetection method for influenza virus based on AC magnetic susceptibility measurement techniques (the DynoMag induction technique) together with functionalized multi-core magnetic nanoparticles. The sample consisting of an incubated mixture of magnetic nanoparticles and rolling circle amplified DNA coils is injected into a tube by a peristaltic pump. The sample is moved as a plug to the two well-balanced detection coils and the dynamic magnetic moment in each position is read over a range of excitation frequencies. The time for making a complete frequency sweep over the relaxation peak is about 5 minutes (10 Hz–10 kHz with 20 data points). The obtained standard deviation of the magnetic signal at the relaxation frequency (around 100 Hz) is equal to about 10−5 (volume susceptibility SI units), which is in the same range obtained with the DynoMag system. The limit of detection with this method is found to be in the range of 1 pM.
Physica C: Superconductivity and its Applications, 2002
given and 72 posters were presented. The book of abstracts and the program venue were published a... more given and 72 posters were presented. The book of abstracts and the program venue were published at the web-site: www.squid2001.org. The book has the complete collection of abstracts (about 124). In this special volume of Physica C, 63 papers from the conference are published. Many people have contributed in creating the SQUID 2001 conference. Harold Weinstock at AFOSR and Horst Rogalla at Twente University (representing ESAS) suggested, initiated and promoted the event. Hans Koch, John Clarke and Tord Claeson gave important input to the conference venue. The chairmen of the different sessions put in a lot of work in organizing balanced and interesting sessions. We are especially indebted to John Clarke for an excellent summary of the scientific contributions and an outlook for the future. Per Magnelind and Alexander Tzalenchuk were responsible for the book of abstracts. Alexander's efficiency and competence made it possible to meet the deadline for submitting this collection of refereed articles to Physica C. Many more people at Chalmers and IMEGO helped out in various ways and the conference would not have succeeded without them.
Physica C: Superconductivity, 2006
The roadmap gives an overview on status and future developments in Superconducting Digital Electr... more The roadmap gives an overview on status and future developments in Superconducting Digital Electronics (SDE). Key areas in SDE under focus are applications, circuit simulation and design, circuit fabrication, interfacing and testing, cooling and system aspects, and new devices and materials. Care was taken to establish the vital link between research and development on the one hand and the industrial view on the other hand. The present roadmap is based on extensive input from the roadmap working group on SDE established by SCENET-the European Network for Superconductivity, intensified by the activities of the FLUXONICS Network-the European Foundry for Superconducting Electronics. It is the result of many years of discussion in the group and of consultations with experts in the field, on the way to bring together industrial expectations and visionary extrapolation and current status of technology.
Nanomaterials
The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO), hosts a quasi-tw... more The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO), hosts a quasi-two-dimensional electron gas (q2DEG), two-dimensional superconductivity, ferromagnetism, and giant Rashba spin-orbit coupling. The co-existence of two-dimensional superconductivity with gate-tunable spin-orbit coupling and multiband occupation is of particular interest for the realization of unconventional superconducting pairing. To investigate the symmetry of the superconducting order parameter, phase sensitive measurements of the Josephson effect are required. We describe an approach for the fabrication of artificial superconducting weak links at the LAO/STO interface using direct high-resolution electron beam lithography and low-energy argon ion beam irradiation. The method does not require lift-off steps or sacrificial layers. Therefore, resolution is only limited by the electron beam lithography and pattern transfer. We have realized superconducting weak links with a barrier thicknes...
On-scalp MEG sensor localization using magnetic dipole-like coils: A method for highly accurate co-registration
NeuroImage
Biosensors
The specific binding of oligonucleotide-tagged 100 nm magnetic nanoparticles (MNPs) to rolling ci... more The specific binding of oligonucleotide-tagged 100 nm magnetic nanoparticles (MNPs) to rolling circle products (RCPs) is investigated using our newly developed differential homogenous magnetic assay (DHMA). The DHMA measures ac magnetic susceptibility from a test and a control samples simultaneously and eliminates magnetic background signal. Therefore, the DHMA can reveal details of binding kinetics of magnetic nanoparticles at very low concentrations of RCPs. From the analysis of the imaginary part of the DHMA signal, we find that smaller MNPs in the particle ensemble bind first to the RCPs. When the RCP concentration increases, we observe the formation of agglomerates, which leads to lower number of MNPs per RCP at higher concentrations of RCPs. The results thus indicate that a full frequency range of ac susceptibility observation is necessary to detect low concentrations of target RCPs and a long amplification time is not required as it does not significantly increase the number ...
Source modelling in magnetoencephalography (MEG) requires precise co-registration of the sensor a... more Source modelling in magnetoencephalography (MEG) requires precise co-registration of the sensor array and the anatomical structure of the measured individual’s head. In conventional MEG, positions and orientations of the sensors relative to each other are fixed and known beforehand, requiring only localization of the head relative to the sensor array. Since the sensors in on-scalp MEG are positioned on the scalp, locations of the individual sensors depend on the subject’s head shape and size. The positions and orientations of on-scalp sensors must therefore be measured at every recording. This can be achieved by inverting conventional head localization, localizing the sensors relative to the head - rather than the other way around.In this study we present a practical method for localizing sensors using magnetic dipole-like coils attached to the subject’s head. We implement and evaluate the method in a set of on-scalp MEG recordings using a 7-channel on-scalp MEG system based on high...
Physica B+C
Superconducting aluminium tunnel junctions, operating in the quasi-particle regime, have been use... more Superconducting aluminium tunnel junctions, operating in the quasi-particle regime, have been used to probe the behaviour of an SIS mixer at photon energies approaching the superconducting gap energy. Comparisons with the performance calculated from the quantum theory of mixing give a very good agreement for a relatively high resistance array of AI junctions.
Physical Review B
We study numerically and analytically the shape of a single fluxon moving in a double stacked Jos... more We study numerically and analytically the shape of a single fluxon moving in a double stacked Josephson junctions (SJJ's) for various junction parameters. We show that the fluxon in a double SJJ's consists of two components, which are characterized by different Swihart velocities and Josephson penetration depths. The weight coefficients of the two components depend on the parameters of the junctions and the velocity of the fluxon. It is shown that the fluxon in SJJ's may have an unusual shape with an inverted magnetic field in the second junction when the velocity of the fluxon is approaching the lower Swihart velocity. Finally, we study the influence of fluxon shape on flux-flow current-voltage characteristics and analyze the spectrum of Cherenkov radiation for fluxon velocity above the lower Swihart velocity. Analytic expression for the wavelength of Cherenkov radiation is derived.
Physical Review B
Static and dynamic properties of stacked Josephson junctions are studied theoretically. An approx... more Static and dynamic properties of stacked Josephson junctions are studied theoretically. An approximate analytic solution for a stack with arbitrary junction parameters was obtained. The analytic solution is in good agreement with numerical simulations. Characteristic penetration depths, Swihart velocities, the lower critical field, the first integral, and the free energy for a stack of nonidentical junctions were derived and studied for different parameters of the stack. We show that attractive interaction of fluxons in adjacent junctions exists in the dynamic state of the stack, leading to appearance of the ''in-phase'' state with fluxons on top of each other. In a given external magnetic field the Gibbs free energy has a number of local minima corresponding to particular fluxon distributions ͑modes͒ in the stack each representing a quasiequilibrium state. For a stack of N junctions each mode would result in N distinct flux-flow branches in the current-voltage characteristic. Taking into account that different modes with equal total number of fluxons are not identical we conclude that the total possible number of flux-flow branches can be much larger than the number of junctions in the stack.
YBaCuO hot-electron bolometer mixer
Physica C, 2000
ABSTRACT
High Voltage Induction Device
Interlayer Coupling and Superconducting Critical Temperature of Bi2Sr1.5La0.5CuO6+δ and Bi2Sr2CaCu2O8+δ: Incommensurate Effects of Pressure
Phys Rev Lett, 1999
... T. Murayama and Y. Ando Electrical Physics Department, Central Research Institute of Electric... more ... T. Murayama and Y. Ando Electrical Physics Department, Central Research Institute of Electric Power Industry, 2-11-1 Iwato-kita, Komae, Tokyo 201 ... This discrep-ancy has also been acknowledged by Anderson [4]. Up to now, the Tl-2201 compound is, however, the only excep ...
Weak links and dc SQUIDS on artificial nonsymmetric grain boundaries in YBa2Cu3O7-d
We have studied weak links and dc--SQUIDs made from pulsed laser deposited YBaâCuâO{sub 7-δ} thi... more We have studied weak links and dc--SQUIDs made from pulsed laser deposited YBaâCuâO{sub 7-δ} thin films on Y--ZrOâ bicrystal substrates. The transport properties of the weak links were studied as a function of the misorientation angle (θ) between the two halves of the bicrystal and an exponential dependence of the weak link critical current density was observed for angles up
Development of an electrowetting-based microfluidic platform for magnetic immunoassays
Micro cooling of squid sensor