You have just seen that laughlins argument explains the quantization of the hall conductance in terms of a pump which moves electrons through the bulk of a hall cylinder, from one edge to the other of the cylinder. Dynamic polarization of nuclear spins is studied in a corbino disk under a breakdown regime of the quantum hall effect qhe. The first four chapters require only basic quantum mechanics. The corbino effect is a phenomenon involving the hall effect, but a disc shaped metal sample is used in place of a rectangular one. Avalanche electron bunching in a corbino disk in the quantum hall.
The hall effect offered the first real proof that electric currents in metals are carried by moving electrons, not by protons. The potential distribution in the quantized hall effect pure. These wave functions are constructed by first pairing up the. Breakdown of the quantum hall effect qhe is commonly associated with an electric field approaching. Magnetotransport studies on critical behavior in the quantum hall. Kwant can be used to simulate metals, graphene, topological insulators, quantum hall effect, superconductivity, spintronics, molecular electronics, any combination of the above, and many other things. We have measured the diffusion thermopower of a quantum hall system in a corbino setup. Consider, as in the last lecture, a corbino disk geometry with an \impurity region shielded by impurityfree rings, with a uniform magnetic eld bplus a variable ab. On the constriction of the hall current in the corbino.
Now we slowly vary ab over a time t 0 by an amount. A concentric electrontemperature gradient is introduced by irradiating microwaves, via a coplanar waveguide. But lets start from the classical hall effect, the famous phenomenon by which a current flows perpendicular to an applied voltage, or vice versa a voltage develops perpendicular to a flowing current. Quantum hall effect 55 skipping cyclotron orbits fourterminal sample configuration to measure the hall and longitudinal resistivities quantum hall effect 56 for a given plateau not a perfect conductor.
Measurement of the hall current density in a corbino. Pdf competition between liquid and solid states in twodimensional electron system is an intriguing problem in condensed matter physics. It is shown that diffusion may be one of the reasons for the variety of observed currentvoltage characteristics. The quantum hall effect phenomenon can be summarized as follows. Fractional quantum hall effect and wigner crystallization in suspended corbino graphene disk. The main experimental devices hall bar and corbino disk are described and the basic experimental facts underlying the quantum hall effect are presented. Measurement of the hall current density in a corbino geometry. Giant fano factor and bistability in a corbino disk in the quantum hall effect breakdown regime article pdf available in journal of physics condensed matter 285. There are surprisingly few dedicated books on the quantum hall effect. This task is challenging since the electric current produced by particles of charge q moving at velocity v, is the same as that produced by parti.
The possibilities of experimentally observing these features of the electrostatic potential distribution along a corbino disk with a transport current under conditions of the quantum hall effect are discussed. The qhe in graphene is one of the most conspicuous phenomena that reveal the exotic nature of. Application of magnetic field normal to the graphene plane causes quantum oscillations of resistance shubnikovde haas effect which evolve to qhe under higher fields novoselov et al. Pdf dynamic nuclear polarization in a quantum hall corbino disk. Abstract we performed noise measurements for a corbino disk in the quantum hall effect breakdown regime. Role of chiral quantum hall edge states in nuclear spin. B 85 2012 195107, which treats disorder within the selfconsistent born approximation.
Our experiments address manybody electron states in a highquality suspended corbino disk fig. Competition between liquid and solid states in twodimensional electron system is an intriguing problem in condensed matter physics. The argument proceeds in parallel with that for the iqhe. Among the various geometries to study the fractional quantum hall effect in two dimensional electron gas, the. The corbino geometry offers two important advantages when. This is a discussion of the details of the currentvoltage characteristics of a 2d corbino disk with a uniform density of mobile carriers in the quantum hall effect plateau. Conductance of a corbino disk in a quantum hall regime. The fractional qhe is evidently prima facie impossible to obtain within an independentelectron picture, since it would appear to require that the extended states be only partially occupied and this would immediately lead to a nonzero value of xx. Consider a corbino disk geometry as shown in the gure below disk with a circular hole in its center with an uniform magnetic eld bperpendicular to its surface, plus a aharonovbohm ab abt ux through its centre. We performed noise measurements for a corbino disk in the quantum hall effect breakdown regime. We study the thermoelectric response of corbino structures in the quantum hall effect using a resistive central heater. Integer and fractional quantum hall effect in suspended.
In the early 1980s several experimental and theoretical studies of the breakdown of qhe were reported. Magnetoresistance is the tendency of a material often ferromagnetic to change the value of its electrical resistance in an externallyapplied magnetic field. Author links open overlay panel masahide yokoi a tohru okamoto a shinji kawaji a takayuki goto masahide yokoi a tohru okamoto a shinji kawaji a takayuki goto. Hakonen low temperature laboratory, department of applied physics, aalto university, po box. Electrical polarization of nuclear spins is studied in a corbino disk under a breakdown regime of the quantum hall effect qhe. Currentvoltage characteristics of corbino disks under. Since the edge channels are completely absent in the corbino disk, we conclude that the electric current flowing in the bulk channel of a quantum hall conductor is relevant to dynamic nuclear polarization dnp. Integer and fractional quantum hall effect in suspended graphene in corbino geometry pertti hakonen low temperature laboratory, department of applied physics, aalto university, espoo, finland we have succeeded in manufacturing highquality suspended graphene samples in corbino geometry. Giant fano factor and bistability in a corbino disk in the quantum hall effect breakdown regime view the table of contents for this issue, or go to the journal homepage for more. Corbino disk a and hall bar b configurations fabricated on the twodimensional electron gas 2deg in an insb quantum well c. Laughlin wave function, fractional charge and statistics. Quantum hall effect integer laughlins argument l b x y v i uniform magnetic field b through corbino disk change of aharonovbohm phase through aharonovbohm phase acts on extended trajectories around the corbino ring extended state pure case r m r m1 shift by one trajectory fixed current singlevalued wave function integer.
However, realization of fractional quantum hall state in corbino disc has been technically difficult and the successful attempt of the 52 state in corbino disc is rare, with only one observation of the 52. The quantum hall effect or integer quantum hall effect is a quantummechanical version of the hall effect, observed in twodimensional electron systems subjected to low temperatures and strong magnetic fields, in which the hall conductance. We study junctions between superconductors mediated by the edge states of a quantumspinhall insulator. Hall conductance using gauge arguments given beautifully by laughlin himself. We present hall effect measurements on highly oriented pyrolytic graphite that indicate the occurrence of the integer quantum hall effect. Measurement of the hall current density in a corbino geometry 2d.
Features of the iv characteristics in the limits of pure. Second, it provides a high resolution at very low longitudinal conductivities. Diffusion thermopower of quantum hall states measured in. The corbino disk is defined by two circular ohmic contacts source s and drain d with. Pdf giant fano factor and bistability in a corbino disk.
Hata t1, arakawa t, chida k, matsuo s, kobayashi k. Breakdown of the integer quantum hall effect qhe at high hall electric fields was anticipated by early corbino disc experiments for simosfets where the finite gate voltage regions for. Corbino geometries 2124, with the purpose of achiev. Josephson current and noise at a superconductorquantum. A concentric electrontemperature gradient is introduced by irradiating microwaves, via a coplanar waveguide, near the outer rim of a circular mesa of a twodimensional electron gas. Fractional quantum hall states of composite fermions. The anomalous role of diffusion in the formation of the currentvoltage characteristics of corbino disks is. Stability of the 52 fractional quantum hall state in a. Dynamic nuclear polarization in a quantum hall corbino. In this work we explore the influence of inplane electric fields on the stability of the 52 fractional quantum hall state realized in corbino geometry. Scaling in the quantum hall regime of graphene corbino. Highperformance thermoelectricity in quantumhall corbino. The corbino disk is defined by two circular ohmic contacts source s and drain d with radii of r 1 95. To see that it does, we can repeat the corbino disc argument of section.
Critical breakdown electric fields at the filling factors of 1, 2, 4 and 6 are in agreement with the critical breakdown hall electric fields in the quantized hall plateaus with these. We present hall effect measurements on highly oriented pyrolytic graphite that indicate the occurrence of the integer quantumhalleffect. To see this, we can return to the simple definition 1. Breakdown of the integer quantum hall effect studied by corbino discs. Because of its shape the corbino disc allows the observation of hall effect based magnetoresistance without the associated hall voltage.
Avalanche electron bunching in a corbino disk in the quantum hall effect breakdown regime. Publishers pdf, also known as version of record includes final page, issue and. Stability of the 52 fractional quantum hall state in a corbino disc. Integer quantum hall effect in graphite sciencedirect. Apr 20, 2017 a sidebyside comparison of the rdnmr signals from hall bar and corbino disk configurations allows us to distinguish the contributions of bulk and edge states to dnp in qhf. In this geometry, the quantum hall edge states counterpropagate at the perimeters of corbino disk and no edge channel is formed between the two electrodes. We show that such junctions exhibit a fractional josephson effect, in which the current phase relation has a 4 rather than a 2 periodicity. Iii, we discuss our numerical results concernig the current distribution and valley. These measurements with onsubstrate graphene corbino disks. On the electrostatic potential distribution in a screened corbino disk carrying a transport current under conditions of the quantum hall effect v. Dynamic nuclear polarization in a quantum hall corbino disk. We present measurements of the thermoelectric voltage developed across the radius of the sample along with a theoretical analysis of these experiments. This effect is a consequence of the conservation of fermion paritythe number of. Shubnikovde haas effect an overview sciencedirect topics.
Kobayashi poster avalanche electron bunching in a corbino disk in the quantum hall effect breakdown. Breakdown of the integer quantum hall effect studied by. Pdf quantum hall effect a brief introduction researchgate. We now move on to the quantum hall effect, the mother of all topological effects in condensed matter physics. Recently we showed that the proximity effect between a superconductor and a threedimensional 3d topological insulator leads to a two. Landau velocity for collective quantum hall breakdown. This is a course on the quantum hall effect, given in tifr, mumbai. A sidebyside comparison of the rdnmr signals from hall bar and corbino disk configurations allows us to distinguish the contributions of bulk and edge states to dnp in qhf. Giant fano factor and bistability in a corbino disk in the quantum. The behavior is in agreement with a recent theory y.
Among the various geometries to study the fractional quantum hall effect in two dimensional electron gas, the corbino disc owns the advantage to probe the bulk properties directly. This is followed by a selfconsistent interpretation of this phenomenon. Mesoscopic valley filter in graphene corbino disk containing. Giant fano factor and bistability in a corbino disk in the. Breakdown of nonconductive state of corbino discs at integer filling factors of landau levels at high sourcedrain voltages has been measured for samples fabricated from gaasal 0. The corbino disk is defined by two circular ohmic contacts source s and drain d with radii of r1 95. We have investigated the distribution of the hall current in a corbino geometry twodimensional electron gas 2deg. Jan 12, 2018 we have investigated tunneling current through a suspended graphene corbino disk in high magnetic fields at the dirac point, i. Avalanche electron bunching in a corbino disk in the quantum hall effect breakdown international symposium on fluctuation and structure out of equilibrium 2015, kyoto, japan, aug. Gyrotropic zener tunneling and nonlinear iv curves in the.
The hall effect also showed that in some substances especially ptype semiconductors, it is more appropriate to think of the current as positive holes moving rather than negative electrons. Corbino geometry outperforms the regular hall bar geometry, as it directly probes the bulk twodimensional electron gas 2deg without having complications due to edge state transport15. Onedimensional conduction channels associated with edge states are often considered as background for solidstate quantum information processing not only in systems showing the quantum hall effect 18, but also in graphene 9, 10 or transition metal dichalcogenide nanoribbons. Since the edge channels are completely absent in the corbino disk.
Compare the situation with the simple electron pump which you studied earlier in the lecture. Giant fano factor and bistability in a corbino disk in the quantum hall effect breakdown regime. Shikin 1 journal of experimental and theoretical physics letters volume 66, pages 581 587 1997 cite this article. Josephson current and noise at a superconductorquantumspin. Our results indicate that the thermoelectric response is originated in the electrons, without effects introduced by. On the constriction of the hall current in the corbino disk. Unconventional fractional quantum hall states and wigner.
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