scholarly journals Spin temperature concept verified by optical magnetometry of nuclear spins

2018 ◽  
Vol 97 (4) ◽  
Author(s):  
M. Vladimirova ◽  
S. Cronenberger ◽  
D. Scalbert ◽  
I. I. Ryzhov ◽  
V. S. Zapasskii ◽  
...  
Keyword(s):  
Nuclear Spins ◽  
Spin Temperature ◽  
Optical Magnetometry ◽  
Temperature Concept

scholarly journals Ultra-deep optical cooling of coupled nuclear spin-spin and quadrupole reservoirs in a GaAs/(Al,Ga)As quantum well

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Mladen Kotur ◽  
Daniel O. Tolmachev ◽  
Valentina M. Litvyak ◽  
Kirill V. Kavokin ◽  
Dieter Suter ◽  
...  
Keyword(s):  
Quantum Well ◽  
Nuclear Spin ◽  
Optical Pumping ◽  
Larmor Frequency ◽  
Spin Splitting ◽  
Magnetic Field Direction ◽  
Nuclear Spins ◽  
Spin Temperature ◽  
Adiabatic Demagnetization ◽  
Selective Cooling

AbstractThe physics of interacting nuclear spins in solids is well interpreted within the nuclear spin temperature concept. A common approach to cooling the nuclear spin system is adiabatic demagnetization of the initial, optically created, nuclear spin polarization. Here, the selective cooling of 75As spins by optical pumping followed by adiabatic demagnetization in the rotating frame is realized in a nominally undoped GaAs/(Al,Ga)As quantum well. The lowest nuclear spin temperature achieved is 0.54 μK. The rotation of 6 kG strong Overhauser field at the 75As Larmor frequency of 5.5 MHz is evidenced by the dynamic Hanle effect. Despite the presence of the quadrupole induced nuclear spin splitting, it is shown that the rotating 75As magnetization is uniquely determined by the spin temperature of coupled spin-spin and quadrupole reservoirs. The dependence of heat capacity of these reservoirs on the external magnetic field direction with respect to crystal and structure axes is investigated.

scholarly journals Spin Temperature and Dynamic Nuclear Polarization. From the History of Researches (1953 – 1983)

Substantia ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 19-34
Author(s):  
Aleksander Kessenikh
Keyword(s):  
Dynamic Nuclear Polarization ◽  
Nuclear Polarization ◽  
Spin Diffusion ◽  
Nuclear Spins ◽  
Spin Temperature ◽  
The Public ◽  
History Of Research ◽  
Nuclear Magnetic Spectroscopy ◽  
History Of

An attempt is proposed in the most concise form to provide the reader with a history of research and applications of dynamic nuclear polarization (DNP). The main attention is paid to the first three decades of DNP research, and the history of the discovery and development of multiparticle DNP and its relationship with the spin temperature approximation are outlined in some detail. The article emphasizes the role of such researchers as Anatol Abraham, Maurice Goldman, Michel Borghini, Thomas Wenckebach, Vadim Atsarkin, Boris Provotorov, Maya Rodak, Mortko Kozhushner, Levan Buishvili, Givi Khutsishvili. As far as possible, the contributions of many other scientists are considered. The establishment of a uniform temperature for nuclear spins due to the effect of spin diffusion was first proposed by Nicholas Blombergen in 1949. The content of the article is based on the bibliography available in the public domains, in particular on the memoirs of the research participants, and first of all on the materials of Atsarkin's 1978 review in Sov. Phys. Uspekhi and on the oral history of the development of the multiparticle concept of DNP effects, recorded from the speeches of the participants of the Moscow seminar "Problems of Magnetic Resonance" in 2001. A simplified description of the effects of DNP and a summary of the history of their discovery is given in section “Introduction”. The shortest biographical data and portraits of participants in the DNP study are given in Appendix 1, and a selected bibliography on the problems of DNP and spin temperatures is given in Appendix 2. The bibliography divided into four sections according to the time and type of publication (I - historical research, memoirs; II – monographs, reviews; III - original publications 1953 - 1983; IV – some original publications of a later time, mainly during the transformation of DNP into an method for the implementation of nuclear magnetic spectroscopy and tomography in the interests of chemistry, biochemistry and medicine). The widespread use of DNP methods is evidenced, for example, by the fact, that by now company Bruker BioSpin has installed about 50 gyrotron based spectrometers for DNP operating upto 593 GHz worldwide to date.

Relaxation and phonon bottleneck of 169Tm nuclear spins in TmPO 4 : evidence for the direct process ?

1985 ◽  
Vol 46 (10) ◽  
pp. 1699-1708 ◽  
Author(s):  
Y. Roinel ◽  
V. Bouffard ◽  
J.-F. Jacquinot ◽  
C. Fermon ◽  
G. Fournier
Keyword(s):  
Nuclear Spins ◽  
Direct Process ◽  
Phonon Bottleneck

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.

Dynamical Nuclear Polarization

2018 ◽  
Author(s):  
M. M. Glazov
Keyword(s):  
Spin Polarization ◽  
Nuclear Spin ◽  
Nuclear Polarization ◽  
Magnetic Moments ◽  
Nonlinear Effects ◽  
Many Body ◽  
Nuclear Spin Polarization ◽  
Optical Resonances ◽  
Dynamical Nuclear Polarization ◽  
Temperature Concept

The transfer of nonequilibrium spin polarization between the electron and nuclear subsystems is studied in detail. Usually, a thermal orientation of nuclei in magnetic field is negligible due to their small magnetic moments, but if electron spins are optically oriented, efficient nuclear spin polarization can occur. The microscopic approach to the dynamical nuclear polarization effect based on the kinetic equation method, along with a phenomenological but very powerful description of dynamical nuclear polarization in terms of the nuclear spin temperature concept is given. In this way, one can account for the interaction between neighbouring nuclei without solving a complex many-body problem. The hyperfine interaction also induces the feedback of polarized nuclei on the electron spin system giving rise to a number of nonlinear effects: bistability of nuclear spin polarization and anomalous Hanle effect, dragging and locking of optical resonances in quantum dots. Theory is illustrated by experimental data on dynamical nuclear polarization.

scholarly journals Fundamental limitations of the mode temperature concept in strongly coupled systems

2020 ◽  
Vol 75 (8) ◽  
pp. 803-807
Author(s):  
Svend-Age Biehs ◽  
Achim Kittel ◽  
Philippe Ben-Abdallah
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Strong Coupling ◽  
Quantum Systems ◽  
Coupled Systems ◽  
Strong Coupling Limit ◽  
Strongly Coupled ◽  
Fundamental Limitations ◽  
Temperature Concept ◽  
Vacuum Gap

AbstractWe theoretically analyze heat exchange between two quantum systems in interaction with external thermostats. We show that in the strong coupling limit the widely used concept of mode temperatures loses its thermodynamic foundation and therefore cannot be employed to make a valid statement on cooling and heating in such systems; instead, the incorrectly applied concept may result in a severe misinterpretation of the underlying physics. We illustrate these general conclusions by discussing recent experimental results reported on the nanoscale heat transfer through quantum fluctuations between two nanomechanical membranes separated by a vacuum gap.

scholarly journals A simulation study investigating potential diffusion-based MRI signatures of microstrokes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rafat Damseh ◽  
Yuankang Lu ◽  
Xuecong Lu ◽  
Cong Zhang ◽  
Paul J. Marchand ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Statistical Power ◽  
Barrel Cortex ◽  
Signal Loss ◽  
Nuclear Spins ◽  
Directional Diffusion ◽  
Ischemic Tissue ◽  
Significant Difference ◽  
Before And After ◽  
Experimental Validations

AbstractRecent studies suggested that cerebrovascular micro-occlusions, i.e. microstokes, could lead to ischemic tissue infarctions and cognitive deficits. Due to their small size, identifying measurable biomarkers of these microvascular lesions remains a major challenge. This work aims to simulate potential MRI signatures combining arterial spin labeling (ASL) and multi-directional diffusion-weighted imaging (DWI). Driving our hypothesis are recent observations demonstrating a radial reorientation of microvasculature around the micro-infarction locus during recovery in mice. Synthetic capillary beds, randomly- and radially-oriented, and optical coherence tomography (OCT) angiograms, acquired in the barrel cortex of mice (n = 5) before and after inducing targeted photothrombosis, were analyzed. Computational vascular graphs combined with a 3D Monte-Carlo simulator were used to characterize the magnetic resonance (MR) response, encompassing the effects of magnetic field perturbations caused by deoxyhemoglobin, and the advection and diffusion of the nuclear spins. We quantified the minimal intravoxel signal loss ratio when applying multiple gradient directions, at varying sequence parameters with and without ASL. With ASL, our results demonstrate a significant difference (p < 0.05) between the signal-ratios computed at baseline and 3 weeks after photothrombosis. The statistical power further increased (p < 0.005) using angiograms measured at week 4. Without ASL, no reliable signal change was found. We found that higher ratios, and accordingly improved significance, were achieved at lower magnetic field strengths (e.g., B0 = 3T) and shorter echo time TE (< 16 ms). Our simulations suggest that microstrokes might be characterized through ASL-DWI sequence, providing necessary insights for posterior experimental validations, and ultimately, future translational trials.

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