Aviad Frydman - Academia.edu (original) (raw)

Papers by Aviad Frydman

Research paper thumbnail of Basics of glasses

Research paper thumbnail of Magneto-transport Measurements of Electrostatically Tuned Disordered In2O3 Films near the Superconductor-Insulator Transition

We have used an electric double layer transistor configuration employing an ionic liquid to modif... more We have used an electric double layer transistor configuration employing an ionic liquid to modify the carrier density and resultant properties of disordered In2O3 films near the superconductor-insulator (SI) transition. By carrier density modulation up to 7 X 10^14 carriers-cm-2, we have been able to traverse the SI transition as well as significantly alter the strength and location of the large magnetoresistance peak found in the insulating regime. We have also been able to correlate the magnetic length associated with the largest magnetoresistance peak with a length scale for granularity of the film obtained from a spectral analysis of surface profile data obtained using atomic force microscopy. The latter suggests that film morphology may play an important role in the peak.

Research paper thumbnail of Granular superconductors and ferromagnets: a proximity-effect-based analogue

Philosophical Magazine B, 2001

We present a model and a set of measurements which demonstrate an analogy between superconducting... more We present a model and a set of measurements which demonstrate an analogy between superconducting and ferromagnetic granular ®lms. For granular ®lms of either Pb or Ni we are able to deposit sequential layers of diOE erent material and measure transport and magnetoresistance measurements in situ. In both cases, individual isolated grains are coupled via an overlayer material which does not possess superconductivity or ferromagnetism of the underlying granular material. This coupling induces long-range order. We compare the two eOE ects and discuss the similarities in terms of proximity eOE ects.

Research paper thumbnail of Mesoscopic phenomena in disordered superconductors

Research paper thumbnail of Magnetoresistance of mesoscopic granular ferromagnets

Physical Review B, 2005

We have performed magnetoresistance (MR) measurements of granular ferromagnets having lateral dim... more We have performed magnetoresistance (MR) measurements of granular ferromagnets having lateral dimensions smaller than 0.5 µm and containing a small number of grains (down to about 100). Compared to macroscopic samples, these granular samples exhibit unusually large saturation fields and MR amplitudes. In addition, the evolution of the magnetoresistance curve as the intergrain distance decreases is qualitatively different than that of large samples. We discuss these results and suggest that they reflect a transition from percolation to quasi single-channel dominated transport.

Research paper thumbnail of Magneto-mechanical effects in nano-magnets

physica status solidi (c), 2004

ABSTRACT

Research paper thumbnail of Proximity Effects in Quench-Condensed Granular Superconductors and Ferromagnets

physica status solidi (b), 2000

ABSTRACT

Research paper thumbnail of Comment on “Memory Effects in an Interacting Magnetic Nanoparticle System”

Physical Review Letters, 2004

Comment on "Memory Effects in an Interacting Magnetic Nanoparticle System" In a recent Letter, Su... more Comment on "Memory Effects in an Interacting Magnetic Nanoparticle System" In a recent Letter, Sun et al. [1] study and discuss memory effects in an interacting nanoparticle system with specific temperature and field protocols. The authors claim that the observed memory effects originate from spin-glass dynamics and that the results are consistent with the hierarchical picture of the spin-glass phase. In this comment, we argue their claims premature by demonstrating that all their experimental curves can be reproduced qualitatively using only a simplified model of isolated nanoparticles [2] with a temperature dependent distribution of relaxation times.

Research paper thumbnail of Zero field resistance dip in magnetic tunnel junctions employing a granular electrode

Physical Review B, 2005

We present magnetoresistance (MR) measurements performed on magnetic tunnel junctions in which on... more We present magnetoresistance (MR) measurements performed on magnetic tunnel junctions in which one of the electrodes is a granular ferromagnetic film. These junctions exhibit a zero field resistance dip. The dip magnitude depends on the size of the grains. We interpret these results as a consequence of the orange peel effect between the continuous ferromagnetic film and the magnetic grains. The coupling is found to be much stronger than that between continuous ferromagnetic layers.

Research paper thumbnail of Universal Voltage Fluctuations in Disordered Superconductors

Physical review letters, 2020

The Aharonov-Casher effect is the analogue of the Aharonov-Bohm effect that applies to neutral pa... more The Aharonov-Casher effect is the analogue of the Aharonov-Bohm effect that applies to neutral particles carrying a magnetic moment. This effect can be manifested by vortices or fluxons flowing in trajectories that encompass an electric charge. These vortices have been predicted to result in a persistent voltage that fluctuates for different sample realizations. Here, we show that disordered superconductors exhibit reproducible voltage fluctuation, which is antisymmetrical with respect to the magnetic field, as a function of various parameters such as the magnetic field amplitude, field orientations, and gate voltage. These results are interpreted as the vortex equivalent of the universal conductance fluctuations typical of mesoscopic disordered metallic systems. We analyze the data in the framework of random matrix theory and show that the fluctuation correlation functions and curvature distributions exhibit behavior that is consistent with Aharonov-Casher physics. The results demo...

Research paper thumbnail of Setup for pressurizing thin films through the superconductor-insulator transition

The Review of scientific instruments, 2021

We describe an experimental setup designed for transport measurement of thin disordered supercond... more We describe an experimental setup designed for transport measurement of thin disordered superconducting films as a function of pressure up to several GPa. We use a specially designed single screw diamond anvil cell that allows the gradual increase of high pressure at cryogenic temperatures. By depositing amorphous films of disordered superconducting indium oxide directly on the diamond, we avoid the effect of pressure-induced structural changes in the substrate. Using this technique, we are able to drive thin films through a pressure tuned superconductor-insulator transition.

Research paper thumbnail of An Analogue Between Superconducting and Itinerant Ferromagnetic Ultrathin Films

Research paper thumbnail of Infinite-randomness fixed point of the quantum superconductor-metal transitions in amorphous thin films

Physical Review B, 2019

The magnetic-field-tuned quantum superconductor-insulator transitions of disordered amorphous ind... more The magnetic-field-tuned quantum superconductor-insulator transitions of disordered amorphous indium oxide films are a paradigm in the study of quantum phase transitions, and exhibit powerlaw scaling behavior. For superconducting indium oxide films with low disorder, such as the ones reported on here, the high-field state appears to be a quantum-corrected metal. Resistance data across the superconductor-metal transition in these films are shown here to obey an activated scaling form appropriate to a quantum phase transition controlled by an infinite randomness fixed point in the universality class of the random transverse-field Ising model. Collapse of the field-dependent resistance vs. temperature data is obtained using an activated scaling form appropriate to this universality class, using values determined through a modified form of power-law scaling analysis. This exotic behavior of films exhibiting a superconductor-metal transition is caused by the dissipative dynamics of superconducting rare regions immersed in a metallic matrix, as predicted by a recent renormalization group theory. The smeared crossing points of isotherms observed are due to corrections to scaling which are expected near an infinite randomness critical point, where the inverse disorder strength acts as an irrelevant scaling variable.

Research paper thumbnail of Local view of superconducting fluctuations

Applied Physics Letters, 2018

Research paper thumbnail of Multiple periodicity in a nanoparticle-based single-electron transistor

Nature Communications, 2017

A single-electron transistor is a nano-device with large potential for low-power applications tha... more A single-electron transistor is a nano-device with large potential for low-power applications that can be used as logic elements in integrated circuits. In this device, the conductance oscillates with a well-defined period due to the Coulomb blockade effect. By using a unique technique, we explore single-electron transistors based on a single metallic nanoparticle with tunable coupling to electric leads. We demonstrate a unique regime in which the transistor is characterized by multi-periodic oscillations of the conductance with gate voltage where the additional periods are harmonics of the basic periodicity of the Coulomb blockade and their relative strength can be controllably tuned. These harmonics correspond to a charge change on the dot by a fraction of the electron charge. The presence of multiple harmonics makes these transistors potential elements in future miniaturization of nano-sized circuit elements.

Research paper thumbnail of Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects

Physical review letters, Jan 9, 2016

Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibriu... more Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state.

Research paper thumbnail of Disorder-induced Andreev reflections in granular metals

Physical Review B, 1999

We have studied the transport properties of SNS structures where N is a disordered Ag film quench... more We have studied the transport properties of SNS structures where N is a disordered Ag film quench condensed into a narrow gap between two superconducting Pb electrodes. This setup enables us to control the disorder of the normal region by sequentially depositing layers of Ag in situ. We find that when the length of the disordered N section is 1.5-2 m the samples exhibit a subgap resistance minimum, which we interpret as evidence for strong Andreev reflection processes. This feature evolves into the usual Blonder-Tinkham-Klapwijk behavior as we reduce the disorder of the N region by increasing the Ag thickness. In samples which are shorter than 1 m, this crossover is absent. We discuss the results within the framework of the ''reflectionless tunneling'' mechanism. ͓S0163-1829͑99͒06713-2͔ PHYSICAL REVIEW B

Research paper thumbnail of Andreev Tunneling in Anderson Insulators

Aps March Meeting Abstracts, Mar 1, 1996

Research paper thumbnail of Andreev tunneling through Anderson Insulators

Research paper thumbnail of The Role of Ultra-Small Magnetic Grains in Disordered Granular Ferromagnets

International Journal of Nanoscience, 2005

We present magnetoresistance (MR) measurements on two unique granular ferromagnetic geometries: n... more We present magnetoresistance (MR) measurements on two unique granular ferromagnetic geometries: nanosized granular systems and magnetic tunnel junctions employing a granular electrode. In both systems the saturation fields of the magnetoresistance as well as the MR magnitudes are much larger than that of usual granular films. We interpret these results as being due to the impact of ultrasmall grains. The presence of such nanograins in a random granular array is usually undetectable since their influence on transport, magnetization and magnetoresistance is negligible. Our samples emphasize the role played by these grains leading to a number of unique effects and potential applications.

Research paper thumbnail of Basics of glasses

Research paper thumbnail of Magneto-transport Measurements of Electrostatically Tuned Disordered In2O3 Films near the Superconductor-Insulator Transition

We have used an electric double layer transistor configuration employing an ionic liquid to modif... more We have used an electric double layer transistor configuration employing an ionic liquid to modify the carrier density and resultant properties of disordered In2O3 films near the superconductor-insulator (SI) transition. By carrier density modulation up to 7 X 10^14 carriers-cm-2, we have been able to traverse the SI transition as well as significantly alter the strength and location of the large magnetoresistance peak found in the insulating regime. We have also been able to correlate the magnetic length associated with the largest magnetoresistance peak with a length scale for granularity of the film obtained from a spectral analysis of surface profile data obtained using atomic force microscopy. The latter suggests that film morphology may play an important role in the peak.

Research paper thumbnail of Granular superconductors and ferromagnets: a proximity-effect-based analogue

Philosophical Magazine B, 2001

We present a model and a set of measurements which demonstrate an analogy between superconducting... more We present a model and a set of measurements which demonstrate an analogy between superconducting and ferromagnetic granular ®lms. For granular ®lms of either Pb or Ni we are able to deposit sequential layers of diOE erent material and measure transport and magnetoresistance measurements in situ. In both cases, individual isolated grains are coupled via an overlayer material which does not possess superconductivity or ferromagnetism of the underlying granular material. This coupling induces long-range order. We compare the two eOE ects and discuss the similarities in terms of proximity eOE ects.

Research paper thumbnail of Mesoscopic phenomena in disordered superconductors

Research paper thumbnail of Magnetoresistance of mesoscopic granular ferromagnets

Physical Review B, 2005

We have performed magnetoresistance (MR) measurements of granular ferromagnets having lateral dim... more We have performed magnetoresistance (MR) measurements of granular ferromagnets having lateral dimensions smaller than 0.5 µm and containing a small number of grains (down to about 100). Compared to macroscopic samples, these granular samples exhibit unusually large saturation fields and MR amplitudes. In addition, the evolution of the magnetoresistance curve as the intergrain distance decreases is qualitatively different than that of large samples. We discuss these results and suggest that they reflect a transition from percolation to quasi single-channel dominated transport.

Research paper thumbnail of Magneto-mechanical effects in nano-magnets

physica status solidi (c), 2004

ABSTRACT

Research paper thumbnail of Proximity Effects in Quench-Condensed Granular Superconductors and Ferromagnets

physica status solidi (b), 2000

ABSTRACT

Research paper thumbnail of Comment on “Memory Effects in an Interacting Magnetic Nanoparticle System”

Physical Review Letters, 2004

Comment on "Memory Effects in an Interacting Magnetic Nanoparticle System" In a recent Letter, Su... more Comment on "Memory Effects in an Interacting Magnetic Nanoparticle System" In a recent Letter, Sun et al. [1] study and discuss memory effects in an interacting nanoparticle system with specific temperature and field protocols. The authors claim that the observed memory effects originate from spin-glass dynamics and that the results are consistent with the hierarchical picture of the spin-glass phase. In this comment, we argue their claims premature by demonstrating that all their experimental curves can be reproduced qualitatively using only a simplified model of isolated nanoparticles [2] with a temperature dependent distribution of relaxation times.

Research paper thumbnail of Zero field resistance dip in magnetic tunnel junctions employing a granular electrode

Physical Review B, 2005

We present magnetoresistance (MR) measurements performed on magnetic tunnel junctions in which on... more We present magnetoresistance (MR) measurements performed on magnetic tunnel junctions in which one of the electrodes is a granular ferromagnetic film. These junctions exhibit a zero field resistance dip. The dip magnitude depends on the size of the grains. We interpret these results as a consequence of the orange peel effect between the continuous ferromagnetic film and the magnetic grains. The coupling is found to be much stronger than that between continuous ferromagnetic layers.

Research paper thumbnail of Universal Voltage Fluctuations in Disordered Superconductors

Physical review letters, 2020

The Aharonov-Casher effect is the analogue of the Aharonov-Bohm effect that applies to neutral pa... more The Aharonov-Casher effect is the analogue of the Aharonov-Bohm effect that applies to neutral particles carrying a magnetic moment. This effect can be manifested by vortices or fluxons flowing in trajectories that encompass an electric charge. These vortices have been predicted to result in a persistent voltage that fluctuates for different sample realizations. Here, we show that disordered superconductors exhibit reproducible voltage fluctuation, which is antisymmetrical with respect to the magnetic field, as a function of various parameters such as the magnetic field amplitude, field orientations, and gate voltage. These results are interpreted as the vortex equivalent of the universal conductance fluctuations typical of mesoscopic disordered metallic systems. We analyze the data in the framework of random matrix theory and show that the fluctuation correlation functions and curvature distributions exhibit behavior that is consistent with Aharonov-Casher physics. The results demo...

Research paper thumbnail of Setup for pressurizing thin films through the superconductor-insulator transition

The Review of scientific instruments, 2021

We describe an experimental setup designed for transport measurement of thin disordered supercond... more We describe an experimental setup designed for transport measurement of thin disordered superconducting films as a function of pressure up to several GPa. We use a specially designed single screw diamond anvil cell that allows the gradual increase of high pressure at cryogenic temperatures. By depositing amorphous films of disordered superconducting indium oxide directly on the diamond, we avoid the effect of pressure-induced structural changes in the substrate. Using this technique, we are able to drive thin films through a pressure tuned superconductor-insulator transition.

Research paper thumbnail of An Analogue Between Superconducting and Itinerant Ferromagnetic Ultrathin Films

Research paper thumbnail of Infinite-randomness fixed point of the quantum superconductor-metal transitions in amorphous thin films

Physical Review B, 2019

The magnetic-field-tuned quantum superconductor-insulator transitions of disordered amorphous ind... more The magnetic-field-tuned quantum superconductor-insulator transitions of disordered amorphous indium oxide films are a paradigm in the study of quantum phase transitions, and exhibit powerlaw scaling behavior. For superconducting indium oxide films with low disorder, such as the ones reported on here, the high-field state appears to be a quantum-corrected metal. Resistance data across the superconductor-metal transition in these films are shown here to obey an activated scaling form appropriate to a quantum phase transition controlled by an infinite randomness fixed point in the universality class of the random transverse-field Ising model. Collapse of the field-dependent resistance vs. temperature data is obtained using an activated scaling form appropriate to this universality class, using values determined through a modified form of power-law scaling analysis. This exotic behavior of films exhibiting a superconductor-metal transition is caused by the dissipative dynamics of superconducting rare regions immersed in a metallic matrix, as predicted by a recent renormalization group theory. The smeared crossing points of isotherms observed are due to corrections to scaling which are expected near an infinite randomness critical point, where the inverse disorder strength acts as an irrelevant scaling variable.

Research paper thumbnail of Local view of superconducting fluctuations

Applied Physics Letters, 2018

Research paper thumbnail of Multiple periodicity in a nanoparticle-based single-electron transistor

Nature Communications, 2017

A single-electron transistor is a nano-device with large potential for low-power applications tha... more A single-electron transistor is a nano-device with large potential for low-power applications that can be used as logic elements in integrated circuits. In this device, the conductance oscillates with a well-defined period due to the Coulomb blockade effect. By using a unique technique, we explore single-electron transistors based on a single metallic nanoparticle with tunable coupling to electric leads. We demonstrate a unique regime in which the transistor is characterized by multi-periodic oscillations of the conductance with gate voltage where the additional periods are harmonics of the basic periodicity of the Coulomb blockade and their relative strength can be controllably tuned. These harmonics correspond to a charge change on the dot by a fraction of the electron charge. The presence of multiple harmonics makes these transistors potential elements in future miniaturization of nano-sized circuit elements.

Research paper thumbnail of Glassy Dynamics in Disordered Electronic Systems Reveal Striking Thermal Memory Effects

Physical review letters, Jan 9, 2016

Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibriu... more Memory is one of the unique qualities of a glassy system. The relaxation of a glass to equilibrium contains information on the sample's excitation history, an effect often refer to as "aging." We demonstrate that under the right conditions a glass can also possess a different type of memory. We study the conductance relaxation of electron glasses that are fabricated at low temperatures. Remarkably, the dynamics are found to depend not only on the ambient measurement temperature but also on the maximum temperature to which the system was exposed. Hence the system "remembers" its highest temperature. This effect may be qualitatively understood in terms of energy barriers and local minima in configuration space and therefore may be a general property of the glass state.

Research paper thumbnail of Disorder-induced Andreev reflections in granular metals

Physical Review B, 1999

We have studied the transport properties of SNS structures where N is a disordered Ag film quench... more We have studied the transport properties of SNS structures where N is a disordered Ag film quench condensed into a narrow gap between two superconducting Pb electrodes. This setup enables us to control the disorder of the normal region by sequentially depositing layers of Ag in situ. We find that when the length of the disordered N section is 1.5-2 m the samples exhibit a subgap resistance minimum, which we interpret as evidence for strong Andreev reflection processes. This feature evolves into the usual Blonder-Tinkham-Klapwijk behavior as we reduce the disorder of the N region by increasing the Ag thickness. In samples which are shorter than 1 m, this crossover is absent. We discuss the results within the framework of the ''reflectionless tunneling'' mechanism. ͓S0163-1829͑99͒06713-2͔ PHYSICAL REVIEW B

Research paper thumbnail of Andreev Tunneling in Anderson Insulators

Aps March Meeting Abstracts, Mar 1, 1996

Research paper thumbnail of Andreev tunneling through Anderson Insulators

Research paper thumbnail of The Role of Ultra-Small Magnetic Grains in Disordered Granular Ferromagnets

International Journal of Nanoscience, 2005

We present magnetoresistance (MR) measurements on two unique granular ferromagnetic geometries: n... more We present magnetoresistance (MR) measurements on two unique granular ferromagnetic geometries: nanosized granular systems and magnetic tunnel junctions employing a granular electrode. In both systems the saturation fields of the magnetoresistance as well as the MR magnitudes are much larger than that of usual granular films. We interpret these results as being due to the impact of ultrasmall grains. The presence of such nanograins in a random granular array is usually undetectable since their influence on transport, magnetization and magnetoresistance is negligible. Our samples emphasize the role played by these grains leading to a number of unique effects and potential applications.