Miklos Csontos

Last Name

Csontos

First Name

Miklos

ORCID

0000-0002-2766-6860

Organisational unit

03974 - Leuthold, Juerg / Leuthold, Juerg

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Publications 1 - 10 of 47

Origins of conductance anomalies in a p-type GaAs quantum point contact
Komijani, Yashar; Csontos, Miklos; Ihn, Thomas Markus; et al. (2013)
Physical Review B
Low-temperature transport measurements on a p-GaAs quantum point contact are presented which reveal the presence of a conductance anomaly that is markedly different from the conventional “0.7 anomaly.” A lateral shift by asymmetric gating of the conducting channel is utilized to identify and separate different conductance anomalies of local and generic origins experimentally. While the more generic 0.7 anomaly is not directly affected by changing the gate configuration, a model is proposed which attributes the additional conductance features to a gate-dependent coupling of the propagating states to localized states emerging due to a nearby potential imperfection. Finite bias conductivity measurements reveal the interplay between the two anomalies consistently with a two-impurity Kondo model.
Anisotropic Zeeman shift in p-type GaAs quantum point contacts
Komijani, Yashar; Csontos, Miklos; Shorubalko, Ivan; et al. (2013)
Europhysics Letters
Low-temperature electrical conductance spectroscopy measurements of quantum point contacts implemented in p-type GaAs/AlGaAs heterostructures are used to study the Zeeman splitting of 1D subbands for both in-plane and out-of-plane magnetic field orientations. The resulting in-plane g-factors agree qualitatively with those of previous experiments on quantum wires while the quantitative differences can be understood in terms of the enhanced quasi-1D confinement anisotropy. The influence of confinement potential on the anisotropy is discussed and an estimate for the out-of-plane g-factor is obtained which, in contrast to previous experiments, is close to the theoretical prediction. © Copyright EPLA, 2013.
A fast operation of nanometer-scale metallic memristors: highly transparent conductance channels in Ag2S devices
Geresdi, Attila; Csontos, Miklos; Gubicza, Agnes; et al. (2014)
Nanoscale
The nonlinear transport properties of nanometer-scale junctions formed between an inert metallic tip and an Ag film covered by a thin Ag2S layer are investigated. Suitably prepared samples exhibit memristive behavior with technologically optimal ON and OFF state resistances yielding to resistive switching on the nanosecond time scale. Utilizing point contact Andreev reflection spectroscopy, we studied the nature of electron transport in the active volume of memristive junctions showing that both the ON and OFF states correspond to truly nanometer-scale, highly transparent metallic channels. Our results demonstrate the merits of Ag2S nanojunctions as nanometer-scale memory cells which can be switched by nanosecond voltage pulses.
Emergence of bound states in ballistic magnetotransport of graphene antidots
Rakyta, Péter; Tóvári, Endre; Csontos, Miklos; et al. (2014)
Physical Review B
An experimental method for detection of bound states around an antidot formed by a hole in a graphene sheet is proposed via measuring the ballistic two-terminal conductance. In particular, we consider the effect of bound states formed by a magnetic field on the two-terminal conductance and show that one can observe Breit-Wigner-like resonances in the conductance as a function of the Fermi level close to the energies of the bound states. In addition, we develop a numerical method utilizing a reduced computational effort compared to the existing numerical recursive Green's function methods.
Multiple Physical Time Scales and Dead Time Rule in Few-Nanometers Sized Graphene–SiOx-Graphene Memristors
Pósa, László; El Abbassi, Maria; Makk, Péter; et al. (2017)
Nano Letters
The resistive switching behavior in SiOx-based phase change memory devices confined by few nanometer wide graphene nanogaps is investigated. Our experiments and analysis reveal that the switching dynamics is not only determined by the commonly observed bias voltage dependent set and reset times. We demonstrate that an internal time scale, the dead time, plays a fundamental role in the system’s response to various driving signals. We associate the switching behavior with the formation of microscopically distinct SiOx amorphous and crystalline phases between the graphene electrodes. The reset transition is attributed to an amorphization process due to a voltage driven self-heating; it can be triggered at any time by appropriate voltage levels. In contrast, the formation of the crystalline ON state is conditional and only occurs after the completion of a thermally assisted structural rearrangement of the as-quenched OFF state which takes place within the dead time after a reset operation. Our results demonstrate the technological relevance of the dead time rule which enables a zero bias access of both the low and high resistance states of a phase change memory device by unipolar voltage pulses.
Anomalous Hall Effect in the (In,Mn)Sb Dilute Magnetic Semiconductor
Mihály, György; Csontos, Miklos; Bordacs, Sándor; et al. (2008)
Physical Review Letters
High magnetic field study of Hall resistivity in the ferromagnetic phase of (In,Mn)Sb allows one to separate its normal and anomalous components. We show that the anomalous Hall term is not proportional to the magnetization, and that it even changes sign as a function of magnetic field. We also show that the application of pressure modifies the scattering process, but does not influence the Hall effect. These observations suggest that the anomalous Hall effect in (In,Mn)Sb is an intrinsic property and supports the application of the Berry phase theory for (III,Mn)V semiconductors. We propose a phenomenological description of the anomalous Hall conductivity, based on a field-dependent relative shift of the heavy- and light-hole valence bands and the split-off band.
Noise diagnostics of graphene interconnects for atomic-scale electronics
Pósa, László; Balogh, Zoltán; Krisztián, Dávid; et al. (2021)
npj 2D Materials and Applications
Graphene nanogaps are considered as essential building blocks of two-dimensional electronic circuits, as they offer the possibility to interconnect a broad range of atomic-scale objects. Here we provide an insight into the microscopic processes taking place during the formation of graphene nanogaps through the detailed analysis of their low-frequency noise properties. Following the evolution of the noise level, we identify the fundamentally different regimes throughout the nanogap formation. By modeling the resistance and bias dependence of the noise, we resolve the major noise-generating processes: atomic-scale junction-width fluctuations in the nanojunction regime and sub-atomic gap-size fluctuations in the nanogap regime. As a milestone toward graphene-based atomic electronics, our results facilitate the automation of an optimized electrical breakdown protocol for high yield graphene nanogap fabrication.
Picosecond Femtojoule Resistive Switching in Nanoscale VO2 Memristors
Schmid, Sebastian Werner; Pósa, László; Török, Tímea Nóra; et al. (2024)
Beyond-Moore computing technologies are expected to provide a sustainable alternative to the von Neumann approach not only by their down-scaling potential but also via exploiting device-level functional complexity at the lowest possible energy consumption. The dynamics of the Mott transition in correlated electron oxides, such as vanadium dioxide, has been identified as a rich and reliable source of such functional complexity. However, its full potential in high-speed and low-power operation has been largely unexplored. We studied nanoscale VO2 devices in a broad-band setup to reveal the speed and energy limitations of their resistive switching operation. Our picosecond time-resolution, real-time resistive switching experiments and numerical simulations demonstrate that tunable low-resistance states can be set by the application of 20 ps long, <1.7 V amplitude voltage pulses at 15 ps incubation times and switching energies starting from 1 fJ. Moreover, we demonstrate that at nanometer-scale device sizes not only the electric field induced insulator-to-metal transition is ultra-fast, but also the thermal conduction limited metal-to-insulator transition can take place at timescales of 100's of picoseconds. These orders of magnitude breakthroughs open the route to the design of high-speed and low-power dynamical circuits for a plethora of neuromorphic computing applications from pattern recognition to numerical optimization.
An ab initio study on resistance switching in hexagonal boron nitride
Ducry, Fabian; Waldhoer, Dominic; Knobloch, Theresia; et al. (2022)
npj 2D Materials and Applications
Two-dimensional materials have been widely investigated to implement memristive devices for data storage or neuromorphic computing applications because of their ultra-scaled thicknesses and clean interfaces. For example, resistance switching in hexagonal boron nitride (h-BN) has been demonstrated. This mechanism is most of the time attributed to the movement of metallic ions. It has however also been reported when h-BN is contacted with two inert electrodes such as graphene or Pt. We suggest here that the switching mechanism of the latter devices, which has not yet been clearly established, relies on locals change of the electronic structure of h-BN as caused by atomic defects, e.g., multi-vacancies. This class of intrinsic h-BN defects can create electrically controllable interlayer bridges. We use a combination of hybrid density functional theory and the Non-equilibrium Green's function formalism to show that a single interlayer bridge resulting from the presence of a trivacancy in a graphene/h-BN/graphene stack leads to a switching voltage of similar to 5 V and a high-to-low resistance ratio >100. Both values lie within the reported experimental range and thus confirm the likelihood that intrinsic defects play a key role in the resistance switching of h-BN in contact with inert electrodes.
Improved thermal relaxation method for the simultaneous measurement of the specific heat and thermal conductivity
Demkó, László; Kézsmárki, Istvan; Csontos, Miklos; et al. (2010)
The European Physical Journal B
A novel method for the simultaneous, high-resolution measurement of the specific heat c and the thermal conductivity κ is presented. A new experimental setup has been developed with special emphasis on the elimination of systematic errors arising from radiative heat loss. A self-consistent data evaluation method is implemented which takes the effects of the sample geometry on c and κ properly into account. The measurements were performed over a broad temperature regime from 3 K up to room temperature on three compounds from the family of strongly correlated electron systems. The differences in their thermal properties and their highly sample-dependent sizes and shapes demonstrate the extended scope of the proposed method.

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Miklos Csontos

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