Nuclear Spin System Research Articles

Robust continuous time crystal in an electron–nuclear spin system

Robust continuous time crystal in an electron–nuclear spin system

Multiple-quantum-coherence dynamics of spin-1 Bose–Einstein condensate during quantum phase transitions

Multiple quantum coherences are often employed to describe quantum many-body dynamics in nuclear spin systems and recently, to characterize quantum phase transitions in trapped ions. Here we investigate the multiple-quantum-coherence dynamics of a spin-1 Bose–Einstein condensate. By adjusting the quadratic Zeeman shift, the condensate exhibits three quantum phases. Our numerical results show that the spectrum of multiple quantum coherence does indeed catch the quantum critical points. More importantly, with only a few low-order multiple quantum coherences, the spin-1 condensate exhibits rich signals of the many-body dynamics, beyond conventional observables. The experimental implementation of such multiple quantum coherence protocol is also discussed.

Cooling of the Nuclear Spin System of a Nanostructure by Oscillating Magnetic Fields.

We propose a method of cooling nuclear spin systems of solid-state nanostructures by applying a time-dependent magnetic field synchronized with spin fluctuations. Optical spin noise spectroscopy is considered a method of fluctuation control. Depending on the mutual orientation of the oscillating magnetic field and the probe light beam, cooling might be either provided by dynamic spin polarization in an external static field or result from population transfer between spin levels without build-up of a net magnetic moment ("true cooling").

More on the demons of thermodynamics

In her article “The demons haunting thermodynamics” (Physics Today, November 2021, page 44), Katie Robertson concludes the introductory historical summary by saying that modern developments in quantum foundations have banished the demons “once and for all.” Unfortunately, no explanation or reference is given for that optimistic but controversial conclusion.Robertson presents Erwin Hahn’s 1950 spin-echo experiments11. E. L. Hahn, Phys. Rev. 80, 580 (1950). https://doi.org/10.1103/PhysRev.80.580 as the realization of Josef Loschmidt’s vision of reversing momentum. But Hahn clearly described his spin-echo experiments as the effect of traditional spin dynamics for noninteracting spins in a spatially inhomogeneous magnetic field. Although the detailed explanation involves many particular subtleties of NMR dynamics in liquids, Hahn’s interpretation does not imply any violation of the “second law”; it uses only the mild assumption that the spin observables are at thermal equilibrium before each start signal. Robertson’s misunderstanding clearly appears when she writes that “atomic spins that have dephased and become disordered are taken back to their earlier state by an RF pulse” and, a few lines later, “it turns out that the spin-echo experiment is a special case; most systems approach equilibrium instead of retracing their steps back to nonequilibrium states.” The spins have not become disordered: The phase of each spin remains directly related to the magnetic field at the spin’s location, and that relationship explains the echo.Two illuminating articles by Won-Kyu Rhim, Alexander Pines, and John Waugh describe spin-echo experiments in which the irreversible time evolution of a coupled nuclear spin system in solids is apparently “reversed” for a limited duration.22. W.-K. Rhim, A. Pines, J. S. Waugh, Phys. Rev. Lett. 25, 218 (1970); https://doi.org/10.1103/PhysRevLett.25.218W.-K. Rhim, A. Pines, J. S. Waugh, Phys. Rev. B 3, 684 (1971). https://doi.org/10.1103/PhysRevB.3.684 As the authors explain, the results arise from uniform spin manipulation and are still consistent with the laws of thermodynamics.Another aspect of Robertson’s article that disturbed me is the lack of discussion of the relations between the actual experiments performed on large (macroscopic) systems and the microscopic-scale models used in attempts to make predictions about those results.Consider a mixture of oxygen and hydrogen at atmospheric pressure and room temperature. Standard thermodynamics and statistical mechanics will lead to excellent predictions of the equation of state, specific heat, and the like. But the standard models ignore the possibility of the chemical reaction producing water. Improved models are needed if one is to allow for, say, a slow, isothermal catalytic reaction or—much more complicated—an explosion in an isolated system at constant volume. Spin systems offer a rich variety of experimental possibilities for external manipulation and observation, but the corresponding models are related to the real experimental situations by complicated transformations and approximations that must be chosen according to the situation under study.Robertson invokes two models in the context of Maxwell’s demon. One is a biological machine using a ratchet-style mechanism. But in the cited article, the abstract carefully indicates that the evolution does not violate the second law because the microscopic mechanism is coupled to the exterior of the system.33. V. Serreli et al., Nature 445, 523 (2007). https://doi.org/10.1038/nature05452 In the demon-style experiment of Robertson’s figure 3, a complete realistic discussion of an actual implementation of the experiment leads to the similar conclusion that the second law is not violated.My conclusion is that demons and the related controversies are features of models and that the interpretation of actual experiments should be subjected to critical examination, preferably by those who performed the experiment and have a complete knowledge of all details.ReferencesSection:ChooseTop of pageReferences <<CITING ARTICLES1. E. L. Hahn, Phys. Rev. 80, 580 (1950). https://doi.org/10.1103/PhysRev.80.580, Google ScholarCrossref, ISI2. W.-K. Rhim, A. Pines, J. S. Waugh, Phys. Rev. Lett. 25, 218 (1970); https://doi.org/10.1103/PhysRevLett.25.218, Google ScholarCrossref, ISIW.-K. Rhim, A. Pines, J. S. Waugh, Phys. Rev. B 3, 684 (1971). https://doi.org/10.1103/PhysRevB.3.684, , Google ScholarCrossref, ISI3. V. Serreli et al., Nature 445, 523 (2007). https://doi.org/10.1038/nature05452, Google ScholarCrossref, ISI© 2023 American Institute of Physics.

Проявление диполь-дипольного и квадрупольного взаимодействий в спектре коррелятора оптически охлажденных ядерных спинов объемного кристалла n-GaAs

In this work, we measured the correlator spectrum of optically cooled nuclear spin system of a bulk n-GaAs crystal in a zero magnetic field. The resulting spectrum is described by two contours, which can be interpreted as the participation of nuclear spins in two types of interactions. We analyzed the measured spectrum in the model for classical magnetic moments in the GaAs lattice. The analysis showed that the main contribution to the high-frequency part of the spectrum is due to the dipole-dipole interaction, and that to the low-frequency part is due to the quadrupole interaction.

Detection of honey adulteration using benchtop 1H NMR spectroscopy.

High magnetic field NMR spectroscopy featuring the use of superconducting magnets is a powerful analytical technique for the detection of honey adulteration. Such high field NMR systems are, however, typically housed in specialised laboratories, require cryogenic coolants, and necessitate specialist training to operate. Benchtop NMR spectrometers featuring permanent magnets are, by comparison, significantly cheaper, more mobile and can be operated with minimal expertise. The lower magnetic fields used in such systems, however, result in limited spectral resolution, which diminishes their ability to perform quantitative composition analysis. These limitations may be overcome by implementing a recently developed field-invariant model-based fitting method which is defined by the underlying quantum mechanical properties of the nuclear spin system; this method is applied here to quantify the sugar composition of honey using benchtop 1H NMR (43 MHz) spectroscopy. The detection of adulteration of 26 honey samples with brown rice syrup is quantitatively demonstrated to a minimum adulterant concentration of 5 wt%. Honey adulteration with corn syrup, glucose syrup and wheat syrup was also quantitatively detected using this approach. Our NMR detection of adulteration was shown to be invariant with time over 60 days of storage.

Non-Steady State NMR Effect and Application on Time-Varying Magnetic Field Measurement.

The measurement of a time-varying magnetic field is different from a constant magnetic field, due to its field intensity variation with time. Usually, the time-varying magnetic field measurement converts the solution of the magnetic induction intensity into the calculation of the induced electromotive force (EMF); then, the magnetic induction intensity is obtained by the time integration of the EMF, but the process is vulnerable to external interference. In this paper, a non-steady state nuclear magnetic resonance (NSS-NMR) scheme for the measurement of a time-varying magnetic field is proposed. In a time-varying magnetic field environment, an RF excitation signal with a certain frequency bandwidth is applied to excite the nuclear spin system. The NSS-NMR signal, which varies with time in the frequency range corresponding to the frequency bandwidth of the RF excitation, could finally be obtained after a series of processing of the probe output signal. During the NSS-NMR experiment, an orthogonal dual-coil probe is adopted to synchronously generate the RF excitation and induce the probe output signal. Moreover, a directional coupler that utilized in the experiment outputs a reference signal from the coupling port for the subsequent signal processing. The experimental results show that the weak NSS-NMR signal is indeed observed. The longitudinal time-varying magnetic field ranges from 0.576 T to 0.582 T, which is inverted by the Larmor precession relationship, have been successfully detected based on the so-called NSS-NMR effect.

Geometric Landau-Zener-Stückelberg-Majorana interferometry for hybrid spin registers

Hybrid systems of electron and nuclear spins are a fundamental building block for scalable quantum information processing. Here we propose a fast and high-fidelity control scheme based on geometric Landau-Zener-St\"uckelberg-Majorana interferometry, using a nitrogen-vacancy center in diamond as an example. When this hybrid spin multilevel system is driven through avoided crossings, geometric phases accumulate in each spin subspace and manifest as interference patterns in the dynamics of the whole system. We systematically study the effects of various decoherence mechanisms and fluctuations of control parameters on this geometric phase process. We also consider the application of quantum memory, where electron spins are used as a processing qubit and nuclear spins are used as a storage qubit. This scheme can achieve a transfer fidelity of 0.985 and a total storage fidelity of 0.96. These results pave the way for geometric coherent manipulations on a variety of hybrid quantum platforms.

Unveiling the electron-nuclear spin dynamics in an n -doped InGaAs epilayer by spin noise spectroscopy

We discuss the implications of a small indium content (3%) in a GaAs epilayer on the electron- and nuclear-spin relaxation due to enhanced quadrupolar effects induced by the strain. Using the weakly perturbative spin-noise spectroscopy, we study the electron-spin relaxation dynamics without explicit excitation. The observed temperature dependence indicates the presence of localized states, which have an increased interaction with the surrounding nuclear spins. Time-resolved spin-noise spectroscopy is then applied to study the relaxation dynamics of the optically pumped nuclear-spin system. It shows a multi-exponential decay with time components, ranging from several seconds to hundreds of seconds. Further, we provide a measurement of the local magnetic field acting between the nuclear spins and discover a strong contribution of quadrupole effects. Finally, we apply the nuclear spin diffusion model, that allows us to estimate the concentration of the localized carrier states and to determine the nuclear spin diffusion constant characteristic for this system.

Observation of quantum phase synchronization in a nuclear-spin system

We report an experimental study of phase synchronization in a pair of interacting nuclear spins subjected to an external drive in nuclear magnetic resonance architecture. A weak transition-selective radio-frequency field applied on one of the spins is observed to cause phase localization, which is experimentally established by measuring the Husimi distribution function under various drive conditions. To this end, we have developed a general interferometric technique to directly extract values of the Husimi function via the transverse magnetization of the undriven nuclear spin. We further verify the robustness of synchronization to detuning in the system by studying the Arnold tongue behavior.

Observation of a four-spin solid effect.

The two-spin solid effect (2SSE) is one of the established continuous wave dynamic nuclear polarization mechanisms that enables enhancement of nuclear magnetic resonance signals. It functions via a state-mixing mechanism that mediates the excitation of forbidden transitions in an electron–nuclear spin system. Specifically, microwave irradiation at frequencies ωμw ∼ ω0S ± ω0I, where ω0S and ω0I are electron and nuclear Larmor frequencies, respectively, yields enhanced nuclear spin polarization. Following the recent rediscovery of the three-spin solid effect (3SSE) [Tan et al., Sci. Adv. 5, eaax2743 (2019)], where the matching condition is given by ωμw = ω0S ± 2ω0I, we report here the first direct observation of the four-spin solid effect (4SSE) at ωμw = ω0S ± 3ω0I. The forbidden double- and quadruple-quantum transitions were observed in samples containing trityl radicals dispersed in a glycerol–water mixture at 0.35 T/15 MHz/9.8 GHz and 80 K. We present a derivation of the 4SSE effective Hamiltonian, matching conditions, and transition probabilities. Finally, we show that the experimental observations agree with the results from numerical simulations and analytical theory.

Simultaneous measurements of nuclear-spin heat capacity, temperature, and relaxation in GaAs microstructures

Heat capacity of the nuclear spin system (NSS) in GaAs-based microstructures has been shown to be much greater than expected from dipolar coupling between nuclei, thus limiting the efficiency of NSS cooling by adiabatic demagnetization. It was suggested that quadrupole interaction induced by some small residual strain could provide this additional reservoir for the heat storage. We check and validate this hypothesis by combining nuclear spin relaxation measurements with adiabatic remagnetization and nuclear magnetic resonance experiments, using electron spin noise spectroscopy as a unique tool for detection of nuclear magnetization. Our results confirm and quantify the role of the quadrupole splitting in the heat storage within NSS and provide additional insight into fundamental, but still actively debated relation between a mechanical strain and the resulting electric field gradients in GaAs.

Quantitative NMR (qNMR) spectroscopy based investigation of the absolute content, stability and isomerization of 25-hydroxyvitamin D2/D3 and 24(R),25-dihydroxyvitamin D2 in solution phase

Vitamin D is an important parameter, in serum/plasma based diagnostic analysis, for the determination of optimal regulation of calcium and phosphate homeostases in the human body, vital for the monitoring/progression of osteomalacia and rickets. Particularly, the quantification of 25-hydroxyvitamin D2, 25-hydroxyvitamin D3 and 24R,25-dihydroxyvitamin D in blood is an excellent indicator for the vitamin D status of a patient. For this purpose, LC–MS/MS methods, based on appropriate vitamin D reference standards, are considered to be ‘gold standard’ for such measurements. We have utilized quantitative NMR spectroscopy to determine the absolute content of these molecules, available as non-certified chemicals, and have determined the stability of these callibrators in borderline polar solvents at room temperature. We have observed significant isomerization of the analytes, which can play a big role in quantification of these analytes by hyphenated LC and GC analytical techniques. Appropriate explanations are given for the observation of new impurities with time in solution phase. The spin system selected for quantitation was determined using relevant 1D and 2D NMR pulse sequences. The advantage of the qNMR approach is that it is based on the quantification of atoms rather than molecular properties (e.g., quantitation by LC/UV, GC, etc.). Since the signals in an NMR spectrum are different nuclear spin-systems dispersed precisely in a magnetic environment, with the intensity being directly proportional to the amount of a particular type of nuclear spin, this technique delivers unparalleled information about the chemical structure and the absolute content.

Analysis of the Coupled Electron and Nuclear Spin Systems from Optically Induced Dynamic Nuclear Polarization in GaAs

Analysis of the Coupled Electron and Nuclear Spin Systems from Optically Induced Dynamic Nuclear Polarization in GaAs

The Application of Little’s Effect and Ferrochemistry for New Approach for Extraction of LIOH from Salar Geothermal Brines

A prior theory of Ferrochemistry and its Laws for Little’s Rules 1, 2 and 3 are applied to systems of nuclear spins and nucleon angular momenta for using applied static magnetic fields, static electric fields, ultrasonic vibrations, and radio frequency waves for stimulating, separating and extracting various cations from geothermal, salar brines. Down the group and families of alkali, alkaline earth and halide ions, considerations are given of variations in e- e- --- e- e- --- e- interactions and e- e- --- nuclear interactions from s to p to d to f subshells with complex inter and intra orbital, subshell and shell interactions. The unique symmetry of s orbital for reversibly collapsing on nuclei and vice versa nuclei fractionally, reversibly fissing for nuclear pressures into s orbitals and from s subshells into outer subshells of higher azimuthal quanta are given. The alterations of the electronic shells and variations among elements and their isotopes are disclosed to cause the novel mechanics for separating the alkali cations and lithium, specifically. An analogy is draw between extractions of Li+, Na+, K+, Mg2+ and Ca2+ cations in graphene-nanodiamond nanofiltering membrane and variations of these ions in ion channels of brain and nervous systems in animals and humans for determining new mechanics of diseases like mania, depression, and bipolar disorder with treatments by Li+ is considered. Advantages of this graphene, nanodiamond nanofilter relative to current methods are considered. Details of the mechanics on basis of varying sizes of s orbitals, symmetries of s orbitals, varying rotation rates of the cations, varying spins of the cations, and varying nuclear magnetic moments (NMMs) of the cations are presented. The originality of the author’s theory of invoking NMMs for differing interactions is contrasted with prior nuclear spin effects of prior investigators. Complex spin and angular momenta interactions of the cations, anions, protons and halides are considered. A novel method of using the static magnetic field, static electric fields, radio frequency waves and ultrasounds for selective precipitations of LiOH (s) with retarding Li2CO3 (s) is presented. The ultrasounds and radio waves may agitate in operation to prevent clogging of the graphene/nanodiamond nanofiltration membrane. On the basis of separation factors (ξ) as by ratios of various NMMs of the cations in geothermal salar brines, the separation factor varies from: ξ(Li+/Na+) = 1.45; to ξ(Li+/K+) = 8.35 to ξ(Co/Li) = 0.607 to ξ(Co/Mn) = 0.635. The similar, large NMMs of Li with Co and Mn with small differences in spins may by the theory here be the explanation and cause for more difficult separation of Li from Co and Mn and the current empirical affinity of Li for Co and Mn as indeed Co and Mn have been observed as sorbents for Li.

Long-range distance determination in fully deuterated RNA with pulsed EPR spectroscopy

Pulsed electron-electron double resonance (PELDOR or DEER) spectroscopy is powerful in structure and dynamics study of biological macromolecules by providing distance distribution information ranging from 1.8 to 6 nm, providing that the biomolecules are site-specifically labeled with paramagnetic tags. However, long distances up to 16 nm have been measured on perdeuterated and spin-labeled proteins in deuterated solvent by PELDOR. Here we demonstrate long-range distance measurement on a large RNA, the 97-nucleotide 3′SL RNA element of the Dengue virus 2 genome, by combining a posttranscriptional site-directed spin labeling method using an unnatural basepair system with RNA perdeuteration by enzymatic synthesis using deuterated nucleotides. The perdeuteration removes the coupling of the electron spins of the nitroxide spin labels from the proton nuclear spin system of the RNA and does extend the observation time windows of PELDOR up to 50 μs. This enables one to determine long distances up to 14 nm for large RNAs and their conformational flexibility.

Warm-up spectroscopy of quadrupole-split nuclear spins in n -GaAs epitaxial layers

The efficiency of the adiabatic demagnetization of the nuclear spin system (NSS) of a solid is limited, if quadrupole effects are present. Nevertheless, despite a considerable quadrupole interaction, recent experiments validated the thermodynamic description of the NSS in GaAs. This suggests that nuclear spin temperature can be used as a probe of nuclear magnetic resonances. We implement this idea by analyzing the modification of the NSS temperature in response to an oscillating magnetic field at various frequencies, an approach termed as the warm-up spectroscopy. It is tested in a $n$-GaAs sample where both mechanical strain and built-in electric field may contribute to the quadrupole splitting, yielding the parameters of electric field gradient tensors for $^{75}\mathrm{As}$ and both Ga isotopes, $^{69}\mathrm{Ga}$ and $^{71}\mathrm{Ga}$.

Peculiarities of Rabi oscillations and free induction decay in two-component nuclear spin systems with Ising nuclei interactions

Nuclear spin systems in manganites, having separation of ferromagnetic and antiferromagnetic phases, which are manifested as two lines in the NMR spectrum, are studied. Taking into account the Ising nuclear interaction, we obtain an analytical description of Rabi oscillations and free induction decay in two-component nuclear spin systems when a radio-frequency pulse non-resonantly excites the nuclei of one magnetic phase and resonantly the nuclei of the other phase. It is revealed that the nonlinearity of interaction between the nuclei of these phases results in additional harmonics in the Rabi oscillations of the non-resonantly excited subsystem. We also show that the Ising interaction inside this subsystem forms multiple echoes in the free induction decay, whereas their non-monotonic damping and amplitude modulation is caused by the spin coupling between the subsystems.

Experimental study of quantum coherence decomposition and trade-off relations in a tripartite system

Quantum coherence is the most fundamental of all quantum quantifiers, underlying other well-known quantities such as entanglement. It can be distributed in a multipartite system in various ways—for example, in a bipartite system it can exist within subsystems (local coherence) or collectively between the subsystems (global coherence), and exhibits a trade-off relation. In this paper, we experimentally verify these coherence trade-off relations in adiabatically evolved nuclear spin systems using an NMR spectrometer. We study the full set of coherence trade-off relations between the original state, the bipartite product state, the tripartite product state, and the decohered product state. We also experimentally verify the monogamy inequality and show that both the quantum systems are polygamous during the evolution. We find that the properties of the state in terms of coherence and monogamy are equivalent. This illustrates the utility of using coherence as a characterization tool for quantum states.

Inside Cover: Unambiguous Tracking of Protein Phosphorylation by Fast High‐Resolution FOSY NMR (Angew. Chem. Int. Ed. 44/2021)

A new suite of 2D FOSY experiments focuses onto one coupled nuclear spin system at a time, that is, a post-translational modification or a structural hotspot in general, with three to five known frequencies. With higher sensitivity and versatility than achievable by traditional experiments, FOSY solves the spectral dispersion problem and obtains only the relevant local NMR signal assignment in a few hours as demonstrated by Vladislav Y. Orekhov and co-workers in their Communication on page 23540 for two phosphorylation sites in the 441-residue IDP Tau.