TRANSPORT IN A BILAYER SYSTEM AT HIGH LANDAU FILLING FACTOR

2009 ◽  
Vol 23 (12n13) ◽  
pp. 2603-2606
Author(s):  
G. M. GUSEV
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Quantum Wells ◽  
Quantum Hall Effect ◽  
Filling Factor ◽  
Quantum Hall ◽  
Perpendicular Magnetic Field ◽  
Shubnikov De Haas Oscillations ◽  
Sdh Oscillations ◽  
Magnetoresistance Oscillations

We have studied Shubnikov de Haas oscillations and the quantum Hall effect in GaAs -double well structures in tilted magnetic fields. We found strong magnetoresistance oscillations as a function of an in-plane magnetic field B∥ at ν = 4N + 3 and ν = 4N + 1 filling factors. At low perpendicular magnetic field B⊥, the amplitude of the conventional Shubnikov-de Haas (SdH) oscillations also exhibits B∥-periodic dependence at fixed values of B⊥. We interpret the observed oscillations as a manifestation of the interference between cyclotron orbits in different quantum wells.

scholarly journals Magnetoconductivity in quasiperiodic graphene superlattices

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
M. de Dios-Leyva ◽  
A. L. Morales ◽  
C. A. Duque
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Oscillatory Behavior ◽  
Fermi Velocity ◽  
Perpendicular Magnetic Field ◽  
Self Similarity ◽  
Integer Quantum Hall Effect ◽  
Integer Quantum

AbstractThe magnetoconductivity in Fibonacci graphene superlattices is investigated in a perpendicular magnetic field B. It was shown that the B-dependence of the diffusive conductivity exhibits a complicated oscillatory behavior whose characteristics cannot be associated with Weiss oscillations, but rather with Shubnikov-de Haas ones. The absense of Weiss oscillations is attributed to the existence of two incommensurate periods in Fibonacci superlattices. It was also found that the quasiperiodicity of the structure leads to a renormalization of the Fermi velocity $$v_{F}$$ v F of graphene. Our calculations revealed that, for weak B, the dc Hall conductivity $$\sigma _{yx}$$ σ yx exhibits well defined and robust plateaux, where it takes the unexpected values $$\pm 4e^{2}/\hslash \left( 2N+1\right) $$ ± 4 e 2 / ℏ 2 N + 1 , indicating that the half-integer quantum Hall effect does not occur in the considered structure. It was finally shown that $$\sigma _{yx}$$ σ yx displays self-similarity for magnetic fields related by $$\tau ^{2}$$ τ 2 and $$\tau ^{4}$$ τ 4 , where $$\tau $$ τ is the golden mean.

FRACTIONAL QUANTUM HALL EFFECT: CONSTRUCTION OF THE HARTREE–FOCK STATE BY USING TRANSLATIONAL COVARIANCE

1994 ◽  
Vol 08 (05) ◽  
pp. 529-579 ◽  
Author(s):  
R. FERRARI
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Landau Level ◽  
Quantum Hall Effect ◽  
Filling Factor ◽  
Quantum Hall ◽  
Fractional Quantum Hall Effect ◽  
Fractional Quantum ◽  
Fractional Quantum Hall ◽  
Hartree Fock

The formalism introduced in a previous paper is used for discussing the Coulomb interaction of many electrons moving in two space-dimensions in the presence of a strong magnetic field. The matrix element of the Coulomb interaction is evaluated in the new basis, whose states are invariant under discrete translations (up to a gauge transformation). This paper is devoted to the case of low filling factor, thus we limit ourselves to the lowest Landau level and to spins all oriented along the magnetic field. For the case of filling factor νf = 1/u we give an Ansatz on the state of many electrons which provides a good approximated solution of the Hartree–Fock equation. For general filling factor νf = u′/u a trial state is given which converges very rapidly to a solution of the self-consistent equation. We generalize the Hartree–Fock equation by considering some correlation: all quantum states are allowed for the u′ electrons with the same translation quantum numbers. Numerical results are given for the mean energy and the energy bands, for some values of the filling factor (νf = 1/2, 1/3, 2/3, 1/4, 3/4, 1/5, 2/5, 3/5, 4/5). Our results agree numerically with the Charge Density Wave approach. The boundary conditions are shown to be very important: only large systems (degeneracy of Landau level over 200) are not affected by the boundaries. Therefore results obtained on small scale systems are somewhat unreliable. The relevance of the results for the Fractional Quantum Hall Effect is briefly discussed.

scholarly journals Quantum Hall–based superconducting interference device

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw8693 ◽  
Author(s):  
Andrew Seredinski ◽  
Anne W. Draelos ◽  
Ethan G. Arnault ◽  
Ming-Tso Wei ◽  
Hengming Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Josephson Junction ◽  
Landau Level ◽  
Carrier Density ◽  
Filling Factor ◽  
Quantum Hall ◽  
Edge States ◽  
Highly Efficient ◽  
Wide Range

We present a study of a graphene-based Josephson junction with dedicated side gates carved from the same sheet of graphene as the junction itself. These side gates are highly efficient and allow us to modulate carrier density along either edge of the junction in a wide range. In particular, in magnetic fields in the 1- to 2-T range, we are able to populate the next Landau level, resulting in Hall plateaus with conductance that differs from the bulk filling factor. When counter-propagating quantum Hall edge states are introduced along either edge, we observe a supercurrent localized along that edge of the junction. Here, we study these supercurrents as a function of magnetic field and carrier density.

FURTHER EVIDENCE FOR A COLLAPSE OF THE EXCHANGE-ENHANCED SPIN SPLITTING IN TWO DIMENSIONAL SYSTEMS

2004 ◽  
Vol 18 (27n29) ◽  
pp. 3597-3602 ◽  
Author(s):  
B. A. PIOT ◽  
D. K. MAUDE ◽  
Z. R. WASILEWSKI ◽  
K. J. FRIEDLAND ◽  
R. HEY ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Quantum Hall Effect ◽  
Good Description ◽  
Quantum Hall ◽  
Exchange Interactions ◽  
Spin Splitting ◽  
Spin Gap ◽  
Integer Quantum Hall Effect ◽  
Integer Quantum

The collapse of spin splitting in the integer quantum Hall effect is investigated for a series of Al x Ga 1-x As / GaAs heterojunctions and quantum wells. Magnetoresistance measurements are performed at mK temperature, and a simple model is developed to simulate spin splitting. As expected a single-electron picture cannot reproduce the observed spin splitting, whereas a phenomenological enhanced-spin gap taking into account exchange interactions between electrons provides a good description. The phenomenological spin gap, which is linear in B at high magnetic field, collapses when the spin splitting collapses. This is consistent with previously proposed disorder-driven destruction of exchange interactions with decreasing magnetic field.

scholarly journals Fractional Quantum Hall Effect in SiGe/Si/SiGe Quantum Wells in Weak Quantizing Magnetic Fields

JETP Letters ◽  
2018 ◽  
Vol 107 (12) ◽  
pp. 794-797 ◽  
Author(s):  
V. T. Dolgopolov ◽  
M. Yu. Melnikov ◽  
A. A. Shashkin ◽  
S.-H. Huang ◽  
C. W. Liu ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Quantum Wells ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Fractional Quantum Hall Effect ◽  
Fractional Quantum ◽  
Fractional Quantum Hall ◽  
Sige Quantum Wells

scholarly journals MAGNETOTRANSPORT IN DILUTE 2D SI-MOSFET SYSTEM

2004 ◽  
Vol 18 (27n29) ◽  
pp. 3609-3612 ◽  
Author(s):  
M. V. CHEREMISIN
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Field Configuration ◽  
Zero Field ◽  
Magnetic Field Configuration ◽  
Valley Splitting ◽  
2D System ◽  
Shubnikov De Haas Oscillations

The beating pattern of Shubnikov-de Haas oscillations is reproduced in crossed magnetic field configuration and in presence of zero-field valley splitting in Si -MOSFET 2D system. The features of Quantum Hall Effect in extremely dilute 2D system are discussed.

scholarly journals THE QUANTUM HALL EFFECT IN GRAPHENE

2012 ◽  
Vol 26 (13) ◽  
pp. 1250084 ◽  
Author(s):  
PAOLO CEA
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fields ◽  
Numerical Simulations ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Landau Levels ◽  
Dynamical Generation ◽  
Dirac Sea

We investigate the quantum Hall effect in graphene. We argue that in graphene in presence of an external magnetic field there is dynamical generation of mass by a rearrangement of the Dirac sea. We show that the mechanism breaks the lattice valley degeneracy only for the n = 0 Landau levels and leads to the new observed ν = ±1 quantum Hall plateaus. We suggest that our result can be tested by means of numerical simulations of planar Quantum Electro Dynamics with dynamical fermions in an external magnetic fields on the lattice.

Quantum Hall Effect in AlGaAs and Graphite Quantum Dots

2013 ◽  
Vol 667 ◽  
pp. 1-9 ◽  
Author(s):  
Keshav N. Shrivastava
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Hall Effect ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Two Dimensional ◽  
Hall Resistivity ◽  
Angular Momenta ◽  
The Difference ◽  
Density Of Electrons

Abstract. The 30 nm wide quantum wells on a 4x4 mm2 piece of GaAs/AlGaAs are formed when the layers of GaAs are deposited on AlGaAs films. The two-dimensional density of electrons is 3x1011 cm-2 and the mobility is 32x106 cm2/Vs. In such a sample the Hall resistivity as a function of magnetic field is not a linear function. Hence a suitable theory to understand the Hall effect is formulated. We find that there are phase transitions as a function of temperature. There are lots of fractions of charge which are explained on the basis of spin and orbital angular momentum of the electron. The nano meter size films of graphite also show that the Hall resistivity is non-linear and shows steps as a function of magnetic field. We make an effort to understand the steps in the Hall effect resistivity of graphite with quantum wells formed on the surface. It is found that the fractions are in four categories, (i) the principal fractions which are determined by spin and orbital angular momenta, (ii) the resonances which occur at the difference between two values such as =1-2, (iii) two-particle states which occur at the sum of the two frequencies and (iv) there are clusters of electrons localized in some areas of the sample. The spin in the clusters is polarized so that it becomes NS which is not 1/2 but depends on the number N, of electrons in a cluster.

scholarly journals The temperature dependence of the conductivity peak values in the single and the double quantum well nanostructures n-InGaAs/GaAs after IR-illumination

2017 ◽  
Vol 51 (2) ◽  
pp. 281
Author(s):  
Yu.G. Arapov ◽  
S.V. Gudina ◽  
A.S. Klepikova ◽  
V.N. Neverov ◽  
G.I. Harus ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Quantum Hall Effect ◽  
Quantum Hall ◽  
Double Quantum ◽  
Integer Quantum Hall Effect ◽  
Double Quantum Well ◽  
Scaling Hypothesis ◽  
Integer Quantum ◽  
Two Parameter

The dependences of the longitudinal and Hall resistances on a magnetic field in n-InGaAs/GaAs heterostructures with a single and double quantum wells after infrared illumination are measured in the range of magnetic fields B=0-16 T and temperatures T=0.05-4.2 K. Analysis of the experimental results was carried out on a base of two-parameter scaling hypothesis for the integer quantum Hall effect. The value of the second (irrelevant) critical exponent of the theory of two-parameter scaling was estimated. DOI: 10.21883/FTP.2017.02.44119.8302

Sign in / Sign up

Export Citation Format

Share Document