Quantum Coherence Engineering in the Integer Quantum Hall Regime

Huynh, P. A.; Portier, F.; Sueur, H. le; Faini, G.; Gennser, U.; Mailly, D.; Pierre, F.; Wegscheider, Werner; Roche, P.

doi:10.1103/physrevlett.108.256802

Cited by 57 publications

(63 citation statements)

References 18 publications

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“…This mechanism is at the heart of the decoherence 9,10,13 and relaxation [14][15][16]12 of electronic excitations propagating in these systems. As such, it has been probed through Mach-Zehnder interferometry [17][18][19] or spectroscopy of edge channels [20][21][22] . This situation bears strong analogies with the spin-charge separation of conventional 1D wires, except that the two spin species are carried by two separated edge channels.…”

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confidence: 99%

Separation of neutral and charge modes in one-dimensional chiral edge channels

et al. 2013

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Coulomb interactions have a major role in one-dimensional electronic transport. They modify the nature of the elementary excitations from Landau quasiparticles in higher dimensions to collective excitations in one dimension. Here we report the direct observation of the collective neutral and charge modes of the two chiral co-propagating edge channels of opposite spins of the quantum Hall effect at filling factor 2. Generating a charge density wave at frequency f in the outer channel, we measure the current induced by inter-channel Coulomb interaction in the inner channel after a 3-mm propagation length. Varying the driving frequency from 0.7 to 11 GHz, we observe damped oscillations in the induced current that result from the phase shift between the fast charge and slow neutral eigenmodes. We measure the dispersion relation and dissipation of the neutral mode from which we deduce quantitative information on the interaction range and parameters.

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confidence: 99%

Separation of neutral and charge modes in one-dimensional chiral edge channels

et al. 2013

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“…(13) and for negative sign, (14) which are same as in (8). In the case of l =0, an interesting situation arises.…”

Section: International Journal Of Applied Physics Andmentioning

confidence: 95%

“…Hence the noise power changes upon change in helicity. Some times the experimentalists [8] use the idea of chirality which is similar to that of helicity defined in the present work as the sign of p.s. The velocity of the electron appears in the helicity so that upstream particles have one helicity while the down stream have another helicity.…”

Section: Noise Power and Helicitymentioning

confidence: 99%

The Quantum Hall Effect: Helicity, Graphite and Graphene

Shrivastava¹

2013

IJAPM

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Abstract-TheHall resistivity is explained to arise from the spin and angular momemtum which leads to fractional charge in a natural way. There are helical orbits for the electrons in a magnetic field so that the + sign in spin gives one helicity while the -sign gives another, which is also related to the sign of the electron velocity. The fractions which arise in the graphite resistivity are explained in terms of principal fractions, resonances, sum processes and clusters. The graphene Hall effect data is explained by using the Landau levels with special treatment of spin. The two layer graphene is well explained. A small number of fractions are explained in terms of sample-dependent clusters which are found in some of the samples. While most of the fractions are a property of pure samples, some of the fractions are induced by the clusters.Index Terms-Graphene, graphite, helicity, quantum hall effect, special spin. I. INTRODUCTIONRecently, we have described the correct theory of the quantum Hall effect as well as explained the origin of 101 fractions found in the experimental data [1]. The cyclotron frequency which appears in the Landau levels is replaced by double valued helical values. The Lande's formula is corrected to include the time-reversed conjugate states. Only the l =0 states are used in the original Landau theory which requires to be modified for finite l value. Since j=l ±s is the total angular momentum keeping only l = 0 leaves out the important effects at high fields. The energy levels which result by these corrections lead to the fractions in the flux-quantized resistivity measured in the Hall effect. The concept of helicity is introduced to understand the right and left moving electrons. Usually the velocity is single valued except that in complex clusters there are rotations which allow two signs of the velocity. Hence, as long as charge is conserved particles can occur with reversed helicity. In a single particle this will not happen but in a cluster it is possible.In this paper, we describe the concept of helicity as applied to the quantum Hall effect of electrons in a high magnetic field and low temperatures and also explain the experimental data of fractions in the Hall effect of graphite and graphene. We look for the evidence of the mixed helicity as well as "reversed helicity". We analyze the experimental data of the quantum Hall effect measurements of noise power to look for the effect of helicity. We find that noise power depends on the helicity. It is possible to heat the samples by a heater wire and monitor the motion of the particles. Hence we explain that while one particle moves to the right, the conjugate will move to the left. This motion of the particles is controlled by the helicity. Hence all particles occur in pairs. The original observation of the quantum Hall effect by von Klitzing et al [2] and Tsui et al. [3] had no theory and the efforts of Laughlin [4] did not yield an interpretation of the data and comparisons with the one-component plasma did not find the ground state...

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“…This phenomenon was observed experimentally in the visibility function ν(V dc ) = (G max − G min )/(G max + G min ), where G is the differential conductance of the interferometer, for a noiseless incident beam and filling factors 2 > ff > 1.5 [13,16,17]. Figure 1 shows an electron micrograph (a) and a schematic (b) of a typical sample, the visibility ν normalized to its value ν 0 at V dc = 0 (c), and the corresponding phase evolution (d).…”

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confidence: 94%

“…At the second beam splitter of the interferometer, this leads to a secondary interference between the collective modes as a function of the applied voltage bias. This model can explain many of the experimental observations [12][13][14][15][16], most importantly the visibility lobes [17] and the phase rigidity of the visibility [1,2].…”

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confidence: 99%

Counting statistics and dephasing transition in an electronic Mach-Zehnder interferometer

et al. 2015

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It was recently suggested that a novel type of phase transition may occur in the visibility of electronic Mach-Zehnder interferometers. Here, we present experimental evidence for the existence of this transition. The transition is induced by strongly non-Gaussian noise that originates from the strong coupling of a quantum point contact to the interferometer. We provide a transparent physical picture of the effect by exploiting a close analogy to the neutrino oscillations of particle physics. In addition, our experiment constitutes a probe of the singularity of the elusive full counting statistics of a quantum point contact. The recent discovery of a lobe-type behavior in the visibility of Aharonov-Bohm oscillations in electronic Mach-Zehnder interferometers (MZI) has triggered extensive theoretical studies in this field. These interferometers were implemented in the edge channels in the integer quantum Hall effect (QHE), mostly for filling factor ff = 2 [see Figs. 1(a) and 1(b)] [1-3]. Many sophisticated theories have been proposed to explain the lobes in the differential visibility of Aharonov-Bohm oscillations as a function of the voltage bias [4][5][6][7][8][9][10][11]. While the central lobe and next side lobe are easy to explain, observation of additional side lobes in a number of experiments is considered to be a puzzling phenomenon. Here, we show that this effect can be explained in a rather simple way, if two interacting edge channels are present. The underlying phenomenon turns out to be very similar to that of neutrino oscillations in high-energy physics: neutrinos oscillate between different flavor states because they are created in a flavor eigenstate, which is not an eigenstate of the Hamiltonian. Similarly, when an electron wave packet is partitioned by a beam splitter, it excites a collective charge mode, which is not an eigenstate of our model Hamiltonian [6]. At the second beam splitter of the interferometer, this leads to a secondary interference between the collective modes as a function of the applied voltage bias. This model can explain many of the experimental observations [12][13][14][15][16], most importantly the visibility lobes [17] and the phase rigidity of the visibility [1,2].Dephasing of the Aharanov-Bohm interference results from random fluctuations of the phase that are averaged out by the detector. In our devices, fluctuations are generated by an additional quantum point contact (QPC-0) in front of the interferometer input, which can be controlled by its transmission probability T 0 . The noisy input current leads to charge fluctuations in the interferometer. The accumulated charge shifts the edge, which leads to the Aharonov-Bohm phase shift. Hence, the strong Coulomb interaction between the edge channels guarantees a strong coupling of the electrons in the interferometer to the noise. The visibility will thus be suppressed by the charge fluctuations induced by partitioning of electrons at QPC-0. Most interestingly, the lobe pattern was predicted to undergo a sudden change at T ...

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Quantum Coherence Engineering in the Integer Quantum Hall Regime

Cited by 57 publications

References 18 publications

Separation of neutral and charge modes in one-dimensional chiral edge channels

Separation of neutral and charge modes in one-dimensional chiral edge channels

The Quantum Hall Effect: Helicity, Graphite and Graphene

Counting statistics and dephasing transition in an electronic Mach-Zehnder interferometer

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