SPATIAL DISTRIBUTION OF KNIGHT SHIFT AROUND QUANTUM HALL EDGE CHANNELS USING RESISTIVELY-DETECTED NMR

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1440-1444
Author(s):  
S. MASUBUCHI ◽  
K. HAMAYA ◽  
T. MACHIDA
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Spatial Distribution ◽  
Knight Shift ◽  
Nuclear Polarization ◽  
Filling Factor ◽  
Quantum Hall ◽  
Electron Spin Polarization ◽  
Local Electron ◽  
Nmr Spectrum ◽  
Edge Channel

We develop a method for studying spatial distribution of the Knight shift using resistively-detected nuclear magnetic resonance (NMR) in an AlGaAs/GaAs quantum Hall device. By controlling the position of the dynamic nuclear polarization with the side-gate voltage, the spatial distribution of the NMR spectrum is investigated in a vicinity of quantum Hall edge channels. The value of Knight shift gradually changes in the region where the local Landau-level filling factor is between ν = 1 and ν = 2, implying that the change of the local electron spin polarization is detected in the edge channel.

scholarly journals Dynamic nuclear polarization and Knight shift measurements in a breakdown regime of integer quantum Hall effect

2008 ◽  
Vol 40 (5) ◽  
pp. 1389-1391 ◽  
Author(s):  
Minoru Kawamura ◽  
Hiroyuki Takahashi ◽  
Satoru Masubuchi ◽  
Yoshiaki Hashimoto ◽  
Shingo Katsumoto ◽  
...  
Keyword(s):  
Hall Effect ◽  
Quantum Hall Effect ◽  
Dynamic Nuclear Polarization ◽  
Knight Shift ◽  
Nuclear Polarization ◽  
Quantum Hall ◽  
Integer Quantum Hall Effect ◽  
Integer Quantum

scholarly journals Augmenting microwave irradiation in MAS DNP NMR samples at 263 GHz

2018 ◽  
Vol 187 ◽  
pp. 01005 ◽  
Author(s):  
Armin Purea ◽  
Benjamin Ell ◽  
Christian Reiter ◽  
Fabien Aussenac ◽  
Frank Engelke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Spatial Distribution ◽  
Magnetic Resonance ◽  
Field Strength ◽  
Nuclear Polarization ◽  
Microwave Field ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Microwave Beam ◽  
Angle Spinning

The magnetic microwave field strength and its detailed spatial distribution in magic-angle spinning (MAS) nuclear magnetic resonance (NMR) probes capable of dynamic nuclear polarization (DNP) is investigated by numerical simulations with the objective to augment the magnetic microwave amplitude by structuring the sample in the mm and sub-mm range and by improving the coupling of the incident microwave beam to the sample. As it will be shown experimentally, both measures lead to an increase of the microwave efficiency in DNP MAS NMR.

Lithography below 100 nm

1983 ◽  
Vol 41 ◽  
pp. 96-99
Author(s):  
L. D. Jackel
Keyword(s):  
Spatial Distribution ◽  
Electron Beam ◽  
Electron Scattering ◽  
Electron Beam Lithography ◽  
Substrate Material ◽  
Local Electron ◽  
Electron Dose ◽  
Positive Resist ◽  
Exposure Process

Most production electron beam lithography systems can pattern minimum features a few tenths of a micron across. Linewidth in these systems is usually limited by the quality of the exposing beam and by electron scattering in the resist and substrate. By using a smaller spot along with exposure techniques that minimize scattering and its effects, laboratory e-beam lithography systems can now make features hundredths of a micron wide on standard substrate material. This talk will outline sane of these high- resolution e-beam lithography techniques.We first consider parameters of the exposure process that limit resolution in organic resists. For concreteness suppose that we have a “positive” resist in which exposing electrons break bonds in the resist molecules thus increasing the exposed resist's solubility in a developer. Ihe attainable resolution is obviously limited by the overall width of the exposing beam, but the spatial distribution of the beam intensity, the beam “profile” , also contributes to the resolution. Depending on the local electron dose, more or less resist bonds are broken resulting in slower or faster dissolution in the developer.

scholarly journals Local incompressibility of fractional quantum Hall states at a filling factor of 3/2

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
L. V. Kulik ◽  
V. A. Kuznetsov ◽  
A. S. Zhuravlev ◽  
V. Umansky ◽  
I. V. Kukushkin
Keyword(s):  
Filling Factor ◽  
Quantum Hall ◽  
Fractional Quantum ◽  
Fractional Quantum Hall ◽  
Quantum Hall States ◽  
Hall States

scholarly journals COULOMB GAP IN THE QUANTUM HALL INSULATOR

2001 ◽  
Vol 15 (10n11) ◽  
pp. 1369-1372 ◽  
Author(s):  
MICHAEL BACKHAUS ◽  
BODO HUCKESTEIN
Keyword(s):  
Filling Factor ◽  
Particle Density ◽  
Quantum Hall ◽  
Correct Treatment ◽  
Coulomb Gap ◽  
Hartree Fock ◽  
Strong Disorder ◽  
Single Particle Density ◽  
Lowest Landau Level ◽  
Classical Point

We calculate numerically the spectrum of disordered electrons in the lowest Landau level at filling factor 1/5 using the self-consistent Hartree-Fock approximation for systems containing up to 400 flux quanta. Special attention is paid to the correct treatment of the q=0 component of the Coulomb interaction. For sufficiently strong disorder, the system is an insulator at this filling factor. We observe numerically a Coulomb gap in the single-particle density of states (DOS). The DOS agrees quantitatively with the predictions for classical point charges.

scholarly journals Competing ν = 5/2 fractional quantum Hall states in confined geometry

2016 ◽  
Vol 113 (44) ◽  
pp. 12386-12390 ◽  
Author(s):  
Hailong Fu ◽  
Pengjie Wang ◽  
Pujia Shan ◽  
Lin Xiong ◽  
Loren N. Pfeiffer ◽  
...  
Keyword(s):  
Quantum Computation ◽  
Filling Factor ◽  
Fault Tolerant ◽  
Quantum Hall ◽  
Point Contact ◽  
Fractional Quantum ◽  
Fractional Quantum Hall ◽  
Topological Quantum ◽  
Quantum Point ◽  
Topological Quantum Computation

Some theories predict that the filling factor 5/2 fractional quantum Hall state can exhibit non-Abelian statistics, which makes it a candidate for fault-tolerant topological quantum computation. Although the non-Abelian Pfaffian state and its particle-hole conjugate, the anti-Pfaffian state, are the most plausible wave functions for the 5/2 state, there are a number of alternatives with either Abelian or non-Abelian statistics. Recent experiments suggest that the tunneling exponents are more consistent with an Abelian state rather than a non-Abelian state. Here, we present edge-current–tunneling experiments in geometrically confined quantum point contacts, which indicate that Abelian and non-Abelian states compete at filling factor 5/2. Our results are consistent with a transition from an Abelian state to a non-Abelian state in a single quantum point contact when the confinement is tuned. Our observation suggests that there is an intrinsic non-Abelian 5/2 ground state but that the appropriate confinement is necessary to maintain it. This observation is important not only for understanding the physics of the 5/2 state but also for the design of future topological quantum computation devices.

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