scholarly journals Ядерная спиновая динамика и флуктуации в анизотропной модели большого ящика

2022 ◽  
Vol 64 (2) ◽  
pp. 206
Author(s):  
А.В. Шумилин ◽  
Д.С. Смирнов
Keyword(s):  
Magnetic Field ◽  
Organic Semiconductors ◽  
Nuclear Spin ◽  
Spin Dynamics ◽  
Spin Model ◽  
Zero Magnetic Field ◽  
Current Fluctuations ◽  
Nuclear Spins ◽  
Spin Noise ◽  
Analytical Expressions

We consider the central spin model in the box approximation taking into account an external magnetic field and the anisotropy of the hyperfine interaction. From the exact Hamiltonian diagonalization we obtain analytical expressions for the nuclear spin dynamics in the limit of many nuclear spins. We predict the nuclear spin precession in zero magnetic field for the case of the anisotropic interaction between electron and nuclear spins. We calculate and describe the nuclear spin noise spectra in the thermodynamic equilibrium. The obtained results can be used for the analysis of the nuclear spin induced current fluctuations in organic semiconductors.

Strong Coupling of Electron and Nuclear Spins: Outlook and Prospects

2018 ◽  
Author(s):  
M. M. Glazov
Keyword(s):  
Energy Spectrum ◽  
Charge Carrier ◽  
Strong Coupling ◽  
Nuclear Spin ◽  
Spin Dynamics ◽  
Spin Polaron ◽  
Nuclear Spins ◽  
Deep Impurity ◽  
Impurity Centers ◽  
Ordered State

In this chapter, some prospects in the field of electron and nuclear spin dynamics are outlined. Particular emphasis is put ona situation where the hyperfine interaction is so strong that it leads to a qualitative rearrangement of the energy spectrum resulting in the coherent excitation transfer between the electron and nucleus. The strong coupling between the spin of the charge carrier and of the nucleus is realized, for example in the case of deep impurity centers in semiconductors or in isotopically purified systems. We also discuss the effect of the nuclear spin polaron, that is ordered state, formation at low enough temperatures of nuclear spins, where the orientation of the carrier spin results in alignment of the spins of nucleus interacting with the electron or hole.

Electron Spin Decoherence by Nuclei

2018 ◽  
Author(s):  
M. M. Glazov
Keyword(s):  
Electron Spin ◽  
Spin Dynamics ◽  
Magnetic Moments ◽  
Host Lattice ◽  
Spin Model ◽  
Relaxation Processes ◽  
Nuclear Spins ◽  
Model Calculations ◽  
Spin Decoherence ◽  
Quantum Mechanical Approach

The discussion of the electron spin decoherence and relaxation phenomena via the hyperfine interaction with host lattice spins is presented here. The spin relaxation processes processes limit the conservation time of spin states as well as the response time of the spin system to external perturbations. The central spin model, where the spin of charge carrier interacts with the bath of nuclear spins, is formulated. We also present different methods to calculate the spin dynamics within this model. Simple but physically transparent semiclassical treatment where the nuclear spins are considered as largely static classical magnetic moments is followed by more advanced quantum mechanical approach where the feedback of electron spin dynamics on the nuclei is taken into account. The chapter concludes with an overview of experimental data and its comparison with model calculations.

scholarly journals Спиновая динамика отрицательно заряженных экситонов в квантовых точках InP/(In,Ga)P в магнитном поле

2020 ◽  
Vol 62 (11) ◽  
pp. 1816
Author(s):  
С.В. Некрасов ◽  
Ю.Г. Кусраев ◽  
И.А. Акимов ◽  
L. Langer ◽  
M. Kotur ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Circular Polarization ◽  
Ground State ◽  
Heavy Hole ◽  
Spin Dynamics ◽  
Nuclear Spins ◽  
Time Resolved ◽  
Exciton Ground State ◽  
Charged Exciton

The dynamics of the photoluminescence negative circular polarization of the InP/(In,Ga)P quantum dots ensemble was studied. We find that in the time-resolved dependences of the polarization there are no oscillations in Voigt magnetic field. Also, with increasing field the polarization declines to zero. Such behavior is attributed to the peculiarities of the negatively charged exciton spin dynamics, particularly, to the fact that in the negatively charged exciton ground state the spin dynamics is governed by the heavy hole. We show that magnetic field depolarization of the photoluminescence occurs once the field of dynamically polarized nuclear spins acting on electron spins is surpassed.

Adiabatic demagnetization at absolute negative temperature: Generation of quantum correlations

2019 ◽  
Vol 17 (03) ◽  
pp. 1950023
Author(s):  
Gregory B. Furman ◽  
Shaul D. Goren ◽  
Victor M. Meerovich ◽  
Vladimir L. Sokolovsky
Keyword(s):  
Magnetic Field ◽  
Negative Temperature ◽  
Quantum Correlations ◽  
Zero Magnetic Field ◽  
Positive Temperature ◽  
Nuclear Spins ◽  
Adiabatic Demagnetization ◽  
Negative Temperatures ◽  
Classical Correlations ◽  
Quantum And Classical Correlations

In this paper, we study behavior of the correlations, both quantum and classical, under adiabatic demagnetization process in systems of nuclear spins with dipole–dipole interactions in an external magnetic field and in the temperature range including positive and negative temperatures. For a two-spin system, analytical expressions for the quantum and classical correlations are obtained. It is revealed that the field dependences of the quantum and classical correlations at positive and negative temperatures are substantially different. This difference most clearly appears in the case of zero magnetic field: at negative temperature, the measures of quantum correlations tend to the maximum values with a temperature increase. At positive temperature, these quantities tend to zero at a decrease of magnetic field. It is also found that, for the nearest-neighboring spins in the same field, the values of concurrence and discord are larger at negative temperatures than at positive ones.

Experimental Tests of Possible Mechanisms for the Organic Magnetoresistive Effect

2007 ◽  
Vol 1032 ◽  
Author(s):  
Tho Duc Nguyen ◽  
James Rybicki ◽  
Yugang Sheng ◽  
Markus Wohlgenannt
Keyword(s):  
Magnetic Field ◽  
Organic Semiconductors ◽  
Electrode Materials ◽  
Spin Dynamics ◽  
Experimental Tests ◽  
Triplet Exciton ◽  
Side Chain ◽  
Singlet Exciton ◽  
Organic Magnetoresistance ◽  
Magnetoresistive Effect

AbstractWe experimentally test three existing models of organic magnetoresistance (OMAR) which are all based on carrier spin dynamics. We first prove that hyperfine field originating from the hydrogen nuclei in organic materials is necessary for observing OMAR by studying C60 sandwich devices using several different electrode materials. We show that C60, unlike many other organic semiconductors, does not exhibit any intrinsic OMAR effect. However, we find that as soon as the carriers in C60 are brought in proximity with hydrogen-containing compounds, either in the form of a polymeric electrode, or side-chain substituents, a weak OMAR effect is observed. Next, we perform charge-induced absorption and electroluminescence spectroscopy in a polyfluorene organic magnetoresistive device. Our experiments allow us to measure the singlet exciton, triplet exciton and polaron densities in a live device under an applied magnetic field, and to distinguish between three models of OMAR. These models are based on different spin-dependent interactions, namely exciton formation, triplet exciton-polaron quenching and bipolaron formation. We show that the singlet exciton, triplet exciton and polaron densities and conductivity all increase with increasing magnetic field. Our data are inconsistent with the exciton formation and triplet-exciton polaron quenching models.

CONTROL OF ELECTRON SPIN DECOHERENCE IN MESOSCOPIC NUCLEAR SPIN BATHS

2008 ◽  
Vol 22 (01n02) ◽  
pp. 27-32
Author(s):  
REN-BAO LIU ◽  
WANG YAO ◽  
L. J. SHAM
Keyword(s):  
Electron Spin ◽  
Nuclear Spin ◽  
Spin Dynamics ◽  
Pair Correlation ◽  
Many Body ◽  
Nuclear Spins ◽  
Spin Decoherence ◽  
The Many ◽  
Mutually Independent ◽  
Correlation Approximation

The electron spin decoherence by nuclear spins in semiconductor quantum dots is caused by quantum entanglement between the electron and the nuclei. The many-body dynamics problem of the interacting nuclear spins can be solved with the pair-correlation approximation which treats the nuclear spin flip-flops as mutually independent. The nuclear spin dynamics can be controlled by simply flipping the electron spin so that the electron is disentangled from the nuclei and hence its lost coherence is restored.

Fictitious spin-12 operators and correlations in quadrupole nuclear spin system

2018 ◽  
Vol 16 (01) ◽  
pp. 1850008 ◽  
Author(s):  
G. B. Furman ◽  
S. D. Goren ◽  
V. M. Meerovich ◽  
V. L. Sokolovsky
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Nuclear Spin ◽  
Physical Phenomenon ◽  
Quantum Correlations ◽  
Zero Magnetic Field ◽  
Pauli Matrices ◽  
Nuclear Spin System ◽  
Classical Correlations ◽  
Limiting Values

The Hamiltonian and the spin operators for a spin 3/2 are represented in the basis formed by the Kronecker productions of the [Formula: see text] Pauli matrices. This reformulation allows us to represent a spin 3/2 as a system of two coupled fictitious spins 1/2. Correlations between these fictitious spins are studied using well-developed methods. We investigate the temperature and field dependences of correlations, such as mutual information, classical correlations, entanglement, and geometric and quantum discords in the fictitious spin-1/2 system describing a nuclear spin 3/2 which is placed in magnetic and inhomogeneous electric fields. It is shown that the correlations between the fictitious spins demonstrate properties which differ from those of real two-spin systems. In contrast to real systems all the correlations between the fictitious spins do not vanish with increasing external magnetic field; at a high magnetic field the correlations tend to their limiting values. Classical correlations, quantum and geometric discords reveal a pronounced asymmetry relative to the measurements on subsystems (fictitious spins) even in a uniform magnetic field and at symmetrical EFG, [Formula: see text]. The correlations depend also on the distribution of external charges, on the parameter of symmetry [Formula: see text]. At [Formula: see text] quantum and geometric discords have finite values in a zero magnetic field. The proposed approach may be useful in analysis of properties of particles with larger angular momentum, can provide the way to discover new physical phenomenon of quantum correlations, and can be a useful tool for similar definitions of other physical quantities of complex systems.

scholarly journals Nuclear spin noise in the central spin model

2018 ◽  
Vol 97 (19) ◽  
Author(s):  
Nina Fröhling ◽  
Frithjof B. Anders ◽  
Mikhail Glazov
Keyword(s):  
Nuclear Spin ◽  
Spin Model ◽  
Spin Noise

scholarly journals Effect of magnetic field on the electron-nuclear spin dynamics in quantum dots

2010 ◽  
Vol 245 ◽  
pp. 012028
Author(s):  
M Yu Petrov ◽  
S V Yakovlev ◽  
I V Ignatiev ◽  
D R Yakovlev ◽  
M Bayer
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Nuclear Spin ◽  
Spin Dynamics

A variational method for calculating nuclear spin-spin interactions in molecules

1957 ◽  
Vol 243 (1233) ◽  
pp. 274-280 ◽  
Keyword(s):  
Magnetic Field ◽  
Nuclear Spin ◽  
Valence Bond ◽  
Wave Functions ◽  
Zero Magnetic Field ◽  
Variation Method ◽  
Magnetic Shielding ◽  
Spin Interactions ◽  
General Variation ◽  
Good Agreement

A general variation method is developed for determining: ( a ) the magnetic shielding of nuclear spin-spin interactions in molecules; ( b ) the electron-coupled nuclear spin-spin interactions in molecules. Using simple valence-bond and molecular-orbital wave functions calculations have been made for the HD molecule. It is concluded that effect ( a ) is small compared with ( b ). Both wave functions lead to values for the zero magnetic field splitting of about 49 c/s, in good agreement with the observed value of 43 c/s.

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