The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
A Siddiki - One of the best experts on this subject based on the ideXlab platform.
-
Hall Resistance anomalies in the integer and fractional quantum Hall regime
Physical Review B, 2020Co-Authors: E Peraticos, A Siddiki, Sanjeev Kumar, M Pepper, I Farrer, D A Ritchie, G A C Jones, J P GriffithsAbstract:Experimental evidence of Resistance anomalies in the high-mobility two-dimensional electron gas (2DEG) formed in the GaAs/AlGaAs heterostructure, in the integer and fractional quantized Hall regime, is shown. The data complement to a good approximation the semianalytic calculations used to describe the formation of integral and fractional incompressible strips. The widths of current-carrying channels were calculated by incorporating the screening properties of the 2DEG and the effect of a magnetic field in the perpendicular mode. The many-body effects of the composite fermions are taken into consideration for the energy gap for the fractional states. It is shown that incompressible strips at the edges for both integer and fractional filling factors coexist in their evanescent phase for a particular range of magnetic fields, resulting in overshoot effects at the Hall Resistance. Specifically, anomalous Hall Resistances were noticed for filling factors $\ensuremath{\nu}$ = $\frac{4}{3}$, $\frac{3}{2}$, $\frac{5}{3}$, $\frac{8}{3}$, 3, $\frac{10}{3}$, $\frac{7}{2}$, and 5. This effect is explained and discussed using the screening theory.
-
semi analytical model of Hall Resistance anomalies overshooting in the fractional quantized Hall effect
European Physical Journal B, 2013Co-Authors: Aysevil Salman, A Siddiki, Ali Ihsan Mese, M B YucelAbstract:We predict Resistance anomalies to be observed at high-mobility two-dimensional electron systems (2DESs) in the fractional quantized Hall regime, where the narrow (L < 10 μm) Hall bar is defined by top gates. A semi-analytic calculation scheme is used to describe the formation of integral and fractional incompressible strips. We incorporate the screening properties of the 2DES, together with the effects of perpendicular magnetic field, to calculate the effective widths of the current carrying channels. The many-body effects are included to our calculation scheme via the energy gap obtained from the well-accepted formulation of the composite fermions. We show that the fractional incompressible strips at the edges, assuming different filling factors, become evanescent and can co-exist in certain magnetic field intervals yielding an overshoot at the Hall Resistance, similar to that of the integral quantized Hall effect. We also provide a mechanism to explain the absence of 1/3 state in Fabry-Perot type interference experiments. A gate defined narrow sample design is proposed to enhance the visibility of fragile effects like interference and overshooting based on our semi-analytical model.
-
evanescent incompressible strips as origin of the observed Hall Resistance overshoot
EPL, 2010Co-Authors: A Siddiki, Erden S Gulebaglan, Boz N Yurdasan, G Bilgec, Aylin Yildiz, I SokmenAbstract:In this work we provide a systematic explanation to the unusual non-monotonic behavior of the Hall Resistance observed in two-dimensional electron systems. We use a semi-analytical model based on the interaction theory of the integer quantized Hall effect to investigate the existence of the anomalous, i.e. overshoot, Hall Resistance RH. The observation of the overshoot Resistance at low magnetic-field edge of the plateaus is elucidated by means of overlapping evanescent incompressible strips, formed due to strong magnetic fields and interactions. Utilizing a self-consistent numerical scheme we also show that, if the magnetic field is decreased the RH decreases to its expected value. The effects of the sample width, temperature, disorder strength and magnetic field on the overshoot peaks are investigated in detail. Based on our findings, we predict a controllable procedure to manipulate the maxima of the peaks, which can be tested experimentally. Our model does not depend on specific and intrinsic properties of the material, provided that a single-particle gap exists.
-
quantum Hall Resistance overshoot in two dimensional 2d electron gases theory and experiment
New Journal of Physics, 2010Co-Authors: Juergen Sailer, A Siddiki, Andreas Wild, V Lang, Dominique BougeardAbstract:We present a systematic experimental investigation of an unusual transport phenomenon observed in two-dimensional (2D) electron gases in Si/SiGe heterostructures under integer quantum Hall effect (IQHE) conditions. This phenomenon emerges under specific experimental conditions and in different material systems. It is commonly referred to as a Hall Resistance overshoot but it lacks a consistent explanation so far. Based on our experimental findings, we have developed a model that accounts for all of our observations in the framework of a screening theory for the IQHE. Within this model, the origin of the overshoot is attributed to a transport regime where current is confined to co-existing evanescent incompressible strips of different filling factors.
-
evanescent incompressible strips as origin of the observed Hall Resistance overshoot
arXiv: Mesoscale and Nanoscale Physics, 2010Co-Authors: A Siddiki, Erden S Gulebaglan, Boz N Yurdasan, G Bilgec, Aylin Yildiz, I SokmenAbstract:In this work we provide a systematic explanation to the unusual non-monotonic behavior of the Hall Resistance observed at two-dimensional electron systems. We use a semi-analytical model based on the interaction theory of the integer quantized Hall effect to investigate the existence of the anomalous, \emph{i.e} overshoot, Hall Resistance $R_{H}$. The observation of the overshoot Resistance at low magnetic field edge of the plateaus is elucidated by means of overlapping evanescent incompressible strips, formed due to strong magnetic fields and interactions. Utilizing a self-consistent numerical scheme we also show that, if the magnetic field is decreased the $R_{H}$ decreases to its expected value. The effects of the sample width, temperature, disorder strength and magnetic field on the overshoot peaks are investigated in detail. Based on our findings, we predict a controllable procedure to manipulate the maxima of the peaks, which can be tested experimentally. Our model does not depend on specific and intrinsic properties of the material, provided that a single particle gap exists.
B Jeanneret - One of the best experts on this subject based on the ideXlab platform.
-
compendium for precise ac measurements of the quantum Hall Resistance
arXiv: Mesoscale and Nanoscale Physics, 2009Co-Authors: F J Ahlers, J Schurr, B Jeanneret, F Overney, B M WoodAbstract:In view of the progress achieved in the field of the ac quantum Hall effect, the Working Group of the Comite Consultatif d'Electricite et Magnetisme (CCEM) on the AC Quantum Hall Effect asked the authors of this paper to write a compendium which integrates their experiences with ac measurements of the quantum Hall Resistance. In addition to the important early work performed at the Bureau International des Poids et Mesures and the National Physical Laboratory, UK, further experience has been gained during a collaboration of the authors' institutes NRC, METAS, and PTB, and excellent agreement between the results of different national metrology institutes has been achieved. This compendium summarizes the present state of the authors' knowledge and reviews the experiences, tests and precautions that the authors have employed to achieve accurate measurements of the ac quantum Hall effect. This work shows how the ac quantum Hall effect can be reliably used as a quantum standard of ac Resistance having a relative uncertainty of a few parts in 10^8.
-
phenomenological model for frequency related dissipation in the quantized Hall Resistance
IEEE Transactions on Instrumentation and Measurement, 2007Co-Authors: B Jeanneret, F OverneyAbstract:Recently, ac measurements of the quantized Hall Resistance have shown a linear relationship between the deviation of the Hall Resistance from the perfectly quantized value DeltaRH and the dissipation in the system represented by the longitudinal resistivity rhoxx ac. In this paper, we present a phenomenological model based on electrodynamic arguments that model this relation. The dissipation is due to the displacement current flowing in the system. All the microscopic features are included in a complex tensorial dielectric susceptibility which remains to be investigated if more physical insight in the ac transport properties of the 2-D electron gas is desired
-
the quantized Hall Resistance towards a primary standard of impedance
Metrologia, 2006Co-Authors: F Overney, B Jeanneret, B Jeckelmann, B M Wood, J SchurrAbstract:In this paper, it is shown that a quantum Hall resistor (QHR) which exhibits a proportionality relationship between the deviation of the Hall Resistance from RK/i and the ac dissipation in the system, represented by ρxx, can be used as a primary standard of ac Resistance. As an example, a calculable quadrifilar resistor was calibrated against the QHR at kilohertz frequencies. The agreement between the calibration using the QHR and the calculated frequency dependence of the quadrifilar resistor is better than 4 parts in 10 8 at 1 kHz. This result is achieved despite the frequency and current dependence of the ac-QHR. The most important criterion to achieve accurate measurements using an ac-QHR standard is to extrapolate the value of the Hall Resistance to zero dissipation.
-
influence of the dissipation in ac measurements of the quantized Hall Resistance
IEEE Transactions on Instrumentation and Measurement, 2005Co-Authors: F Overney, B Jeanneret, B M Wood, J SchurrAbstract:A systematic investigation of the current and frequency dependence of the quantum Hall Resistance (QHR) and of the longitudinal resistivity has been carried out at low temperature at the center of the plateau i=2. The deviation of the QHR from the von Klitzing constant is found to be proportional to the longitudinal resistivity and extrapolates to zero, within the measurement uncertainty, when the dissipation in the two-dimensional electron gas vanishes.
-
effects of metallic gates on ac measurements of the quantum Hall Resistance
IEEE Transactions on Instrumentation and Measurement, 2003Co-Authors: F Overney, B Jeanneret, B JeckelmannAbstract:Using a sample with a split back gate, a linear frequency dependence of the AC quantum Hall Resistance (QHR) was observed. The frequency coefficient, which is due to dielectric losses produced by leakage current between the two-dimensional electron gas (2DEG) and the back gates, can be turned from a positive to a negative value by increasing the back-gate voltage. More interestingly, by removing these back gates, the losses can be considerably reduced, leading to a residual frequency coefficient on the order of (0.03/spl plusmn/0.03)/spl times/10/sup -6//kHz. Moreover, at 1 kHz, an extremely flat plateau was observed over a magnetic field range of 1.4 T. These results clearly indicate that the audio frequency dependence of the QHR is to a large extent related to the measurement apparatus and does not originate from the physical transport properties of the 2DEG.
Sergey Kubatkin - One of the best experts on this subject based on the ideXlab platform.
-
operation of graphene quantum Hall Resistance standard in a cryogen free table top system
2D Materials, 2015Co-Authors: T.j.b.m. Janssen, J M Williams, Alexander Tzalenchuk, Sergey Kubatkin, Samuel Laraavila, S Rozhko, I Antonov, Z Melhem, Rositsa YakimovaAbstract:We demonstrate quantum Hall Resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8 K and magnetic fields below 5 T. Operating this system requires little experimental knowledge or laboratory infrastructure, thereby greatly advancing the proliferation of primary quantum standards for precision electrical metrology. This significant advance in technology has come about as a result of the unique properties of epitaxial graphene on SiC.
-
anomalously strong pinning of the filling factor nu 2 in epitaxial graphene
Physical Review B, 2011Co-Authors: T.j.b.m. Janssen, Rositsa Yakimova, Alexander Tzalenchuk, Sergey Kubatkin, Samuel Laraavila, Sergey Kopylov, Vladimir I FalkoAbstract:We explore the robust quantization of the Hall Resistance in epitaxial graphene grown on Si-terminated SiC. Uniquely to this system, the dominance of quantum over classical capacitance in the charge transfer between the substrate and graphene is such that Landau levels (in particular, the one at exactly zero energy) remain completely filled over an extraordinarily broad range of magnetic fields. One important implication of this pinning of the filling factor is that the system can sustain a very high nondissipative current. This makes epitaxial graphene ideally suited for quantum Resistance metrology, and we have achieved a precision of 3 parts in 1010 in the Hall Resistance-quantization measurements.
-
towards a quantum Resistance standard based on epitaxial graphene
Nature Nanotechnology, 2010Co-Authors: Alexander Tzalenchuk, T.j.b.m. Janssen, Samuel Laraavila, Vladimir I Falko, Rositza Yakimova, Alexei Kalaboukhov, Sara Paolillo, Mikael Syvajarvi, Olga Kazakova, Sergey KubatkinAbstract:The quantum Hall effect(1) allows the international standard for Resistance to be defined in terms of the electron charge and Planck's constant alone. The effect comprises the quantization of the Hall Resistance in two-dimensional electron systems in rational fractions of R-K = h/e(2) = 25 812.807 557(18) Omega, the Resistance quantum(2). Despite 30 years of research into the quantum Hall effect, the level of precision necessary for metrology-a few parts per billion-has been achieved only in silicon and III-V heterostructure devices(3-5). Graphene should, in principle, be an ideal material for a quantum Resistance standard(6), because it is inherently two-dimensional and its discrete electron energy levels in a magnetic field (the Landau levels(7)) are widely spaced. However, the precisions demonstrated so far have been lower than one part per million(8). Here, we report a quantum Hall Resistance quantization accuracy of three parts per billion in monolayer epitaxial graphene at 300 mK, four orders of magnitude better than previously reported. Moreover, by demonstrating the structural integrity and uniformity of graphene over hundreds of micrometres, as well as reproducible mobility and carrier concentrations across a half-centimetre wafer, these results boost the prospects of using epitaxial graphene in applications beyond quantum metrology.
-
sic graphene suitable for quantum Hall Resistance metrology
Nature Nanotechnology, 2009Co-Authors: Samuel Laraavila, Alexander Tzalenchuk, Vladimir I Falko, Rositza Yakimova, Alexei Kalaboukhov, Sara Paolillo, Mikael Syvajarvi, Sergey KubatkinAbstract:We report the first observation of the quantum Hall effect in epitaxial graphene. The result described in the submitted manuscript fills the yawning gap in the understanding of the electronic properties of this truly remarkable material and demonstrate suitability of the silicon carbide technology for manufactiring large area high quality graphene. Having found the quantum Hall effect in several devices produced on distant parts of a single large-area wafer, we can confirm that material synthesized on the Si-terminated face of SiC promises a suitable platform for the implementations of quantum Resistance metrology at elevated temperatures and, in the longer term, opens bright prospects for scalable electronics based on graphene.
X C Xie - One of the best experts on this subject based on the ideXlab platform.
-
topological system with a twisting edge band a position dependent Hall Resistance
Physical Review B, 2012Co-Authors: Xuele Liu, Qingfeng Sun, X C XieAbstract:We study a $\ensuremath{\nu}=1$ topological system with one twisting edge-state band and one normal edge-state band. For the twisting edge-state band, Fermi energy goes through the band three times, thus having three edge states on one side of the sample, while the normal edge band contributes only one edge state on the other side of the sample. In such a system, we show that it consists of both topologically protected and unprotected edge states, and as a consequence, its Hall Resistance depends on the location where the Hall measurement is done even for a translationally invariant system. This unique property is absent in a normal topological insulator.
-
topological insulator a new quantized spin Hall Resistance robust to dephasing
Physical Review Letters, 2009Co-Authors: Hua Jiang, Shuguang Cheng, Qingfeng Sun, X C XieAbstract:The dephasing effect on the quantum spin Hall effect (QSHE) is studied. Without dephasing, the longitudinal Resistance in a QSHE system exhibits the quantum plateaus. We find that these quantum plateaus are robust against the normal dephasing but fragile with the spin dephasing. Thus, these quantum plateaus survive only in mesoscopic samples. Moreover, the longitudinal Resistance increases linearly with the sample length but is insensitive to the sample width. These characters are in excellent agreement with the recent experimental results [Science 318, 766 (2007)]. In addition, we define a new spin Hall Resistance that also exhibits quantum plateaus. In particular, these plateaus are robust against any type of dephasing and therefore, survive in macroscopic samples and better reflect the topological nature of QSHE.
B Jeckelmann - One of the best experts on this subject based on the ideXlab platform.
-
the quantized Hall Resistance towards a primary standard of impedance
Metrologia, 2006Co-Authors: F Overney, B Jeanneret, B Jeckelmann, B M Wood, J SchurrAbstract:In this paper, it is shown that a quantum Hall resistor (QHR) which exhibits a proportionality relationship between the deviation of the Hall Resistance from RK/i and the ac dissipation in the system, represented by ρxx, can be used as a primary standard of ac Resistance. As an example, a calculable quadrifilar resistor was calibrated against the QHR at kilohertz frequencies. The agreement between the calibration using the QHR and the calculated frequency dependence of the quadrifilar resistor is better than 4 parts in 10 8 at 1 kHz. This result is achieved despite the frequency and current dependence of the ac-QHR. The most important criterion to achieve accurate measurements using an ac-QHR standard is to extrapolate the value of the Hall Resistance to zero dissipation.
-
revised technical guidelines for reliable dc measurements of the quantized Hall Resistance
Metrologia, 2003Co-Authors: F Delahaye, B JeckelmannAbstract:This paper describes the main tests and precautions necessary for both reproducible and accurate results in the use of the quantum Hall effect as a means to establish a reference standard of dc Resistance having a relative uncertainty of a few parts in 109.
-
effects of metallic gates on ac measurements of the quantum Hall Resistance
IEEE Transactions on Instrumentation and Measurement, 2003Co-Authors: F Overney, B Jeanneret, B JeckelmannAbstract:Using a sample with a split back gate, a linear frequency dependence of the AC quantum Hall Resistance (QHR) was observed. The frequency coefficient, which is due to dielectric losses produced by leakage current between the two-dimensional electron gas (2DEG) and the back gates, can be turned from a positive to a negative value by increasing the back-gate voltage. More interestingly, by removing these back gates, the losses can be considerably reduced, leading to a residual frequency coefficient on the order of (0.03/spl plusmn/0.03)/spl times/10/sup -6//kHz. Moreover, at 1 kHz, an extremely flat plateau was observed over a magnetic field range of 1.4 T. These results clearly indicate that the audio frequency dependence of the QHR is to a large extent related to the measurement apparatus and does not originate from the physical transport properties of the 2DEG.
-
effects of metallic gates on ac measurements of the quantum Hall Resistance
arXiv: Mesoscale and Nanoscale Physics, 2003Co-Authors: F Overney, B Jeanneret, B JeckelmannAbstract:Using a sample with a split back-gate, a linear frequency dependence of the ac quantum Hall Resistance was observed. The frequency coefficient, which is due to dielectric losses produced by leakage current between the 2DEG and the back-gates, can be turned from a positive to a negative values by increasing the back-gate voltage. More interestingly, by removing theses back-gates, the losses can be considerably reduced leading to a residual frequency coefficient on the order of (0.03+-0.03) ppm/kHz. Moreover, at 1 kHz, an extremely flat plateau was observed over a magnetic field range of 1.4 T. These results clearly indicate that the audio frequency dependence of the QHR is to a large extend related to the measurement apparatus and does not originate from the physical transport properties of the 2DEG.
-
the quantum Hall effect as an electrical Resistance standard
Reports on Progress in Physics, 2001Co-Authors: B Jeckelmann, B JeanneretAbstract:The quantum Hall effect (QHE) provides an invariant reference for Resistance linked to natural constants. It is used worldwide to maintain and compare the unit of Resistance. The reproducibility reached today is almost two orders of magnitude better than the uncertainty of the determination of the ohm in the international system of units SI. In this article, mainly the aspects of the QHE relevant for its metrological application are reviewed. After a short introduction of the theoretical models describing the integer QHE, the properties of the devices used in metrology and the measurement techniques are described. A detailed summary is given on the measurements carried out to demonstrate the universality of the quantized Hall Resistance and to assess all the effects leading to deviations of the Hall Resistance from the quantized value. In addition, the present and future role of the QHE in the SI and the field of natural constants is discussed.
