Spin Waves and Spin Currents in Magnon-Phonon Composite Resonator Induced by Acoustic Waves of Various Polarizations

In this work, we present the results of a systematic experimental study of linear and parametric spin wave resonant excitation accompanied by spin currents (spin pumping) in a multifrequency composite bulk acoustic wave resonator with a ZnO-YIG-GGG-YIG/Pt structure. The features of magnetic dynamics excitation in YIG films due to magnetoelastic coupling with acoustic thickness modes of various polarizations are studied. Acoustic spin waves and spin pumping are detected by simultaneous frequency-field mapping of the inverse spin Hall effect voltage and the resonant frequencies of thickness extensional modes. In the parametric range of frequencies and fields, acoustic spin pumping induced by both shear and longitudinal polarization modes was observed. Linear acoustic spin waves are excited only by shear thickness extensional modes because longitudinal acoustic waves do not couple with the magnetic subsystem in linear regime

Entanglement Measures for Single- and Multi-Reference Correlation Effects

Electron correlation effects are essential for an accurate ab initio description of molecules. A quantitative a priori knowledge of the single- or multi-reference nature of electronic structures as well as of the dominant contributions to the correlation energy can facilitate the decision regarding the optimum quantum chemical method of choice. We propose concepts from quantum information theory as orbital entanglement measures that allow us to evaluate the single- and multi-reference character of any molecular structure in a given orbital basis set. By studying these measures we can detect possible artifacts of small active spaces.Comment: 14 pages, 4 figure

СТАБИЛЬНЫЕ ЭЛЕКТРОННО-ЯДЕРНЫЕ СПИНОВЫЕ СИСТЕМЫ NV–13C В АЛМАЗЕ ДЛЯ КВАНТОВЫХ ТЕХНОЛОГИЙ

Using the methods of computational chemistry, we calculated matrices AKL describing hyperfine interactions (HFI) between the electron spin of the color ‘nitrogen-vacancy’ center (NV center) in a diamond and a 13C nuclear spin located somewhere in the Н-terminated carbon cluster C510[NV]H252 hosting the NV center. The rates W0 of the 13C spin flip-flops induced by anisotropic HFI are calculated systematically for all possible locations of 13C in the cluster. It is shown that in the cluster, there are specific positions of nuclear 13C spin, in which it almost does not undergo such flip-flops due to small off-diagonal elements in corresponding matrices AKL. Spatial locations of the 13C stability positions in the cluster are discovered and characteristic splitting values in the spectra of optically detected magnetic resonance (ODMR) for the stable NV–13C systems are calculated, which can be utilized to identify them during their experimental search for use in emerging quantum technologies. It is shown that the positions of the 13C nuclear spin located on the NV center symmetry axis are completely stable (W0 = 0). The characteristics of eight ‘axial’ NV–13C systems are elucidated. The presence of additional ‘non-axial’ near-stable NV–13C spin systems also exhibiting very low flip-flop rates (W0 → 0) due to a high local symmetry of the spin density distribution resulting in vanishing the off-diagonal HFI matrix AKL elements for such systems is revealed for the first time. Spatially, these ‘non-axial’ stable NV–13C systems are located near the plane passing through the vacancy of the NV center and being perpendicular to the NV axis. Analysis of the available publications showed that apparently, some of the predicted stable NV–13C systems have already been observed experimentally. Методами компьютерной химии рассчитаны матрицы AKL, описывающие сверхтонкое взаимодействие (СТВ) электронного спина центра окраски «азот-вакансия» (NV-центра) в алмазе с ядерным спином атома 13С, который расположен в одном из возможных узлов решетки в пассивированном водородом углеродном кластере С510[NV]H252. Выполнен систематический анализ скоростей W0 переворотов ядерных спинов 13С, индуцируемых их анизотропным СТВ с электронным спином NV-центра. Показано, что в кластере имеются специфические позиции ядерного спина 13С, в которых он практически не испытывает таких переворотов вследствие малости недиагональных элементов в соответствующих матрицах AKL. Определено пространственное расположение найденных позиций стабильности в кластере относительно NV-центра и рассчитаны величины характерных расщеплений в спектрах оптически детектируемого магнитного резонанса (ОДМР) для стабильных систем NV–13C, по которым их можно идентифицировать в процессе их экспериментального поиска для использования в разрабатываемых квантовых технологиях. Показано, что полностью стабильными (W0 = 0) являются позиции ядерного спина, расположенные на оси симметрии NV-центра. Найдены характеристики восьми таких «осевых» систем NV–13C. Впервые обнаружено наличие в кластере дополнительных «неосевых» квазистабильных систем NV–13C, имеющих малые скорости переворотов (W0 .→0) спина 13С вследствие высокой локальной симметрии распределения спиновой плотности, обусловливающей малость недиагональных элементов матриц СТВ для таких систем. Пространственно «не осевые» стабильные системы NV–13C расположены в плоскости, проходящей через вакансию NV-центра перпендикулярно его оси. Выполненный анализ имеющихся литературных данных показал, что, по-видимому, некоторые из предсказанных стабильных систем NV–13C уже наблюдались экспериментально.

Frequency and magnetic field mapping of magnetoelastic spin pumping in high overtone bulk acoustic wave resonator

We report on the first observation of microvolt-scale inverse spin Hall effect (ISHE) dc voltage driven by an acoustic spin pumping (ASP) in a bulk acoustic wave (BAW) resonator formed by a Al-ZnO-Al-YIG(1)-GGG-YIG(2)-Pt structure. When 2 mW power is applied to an Al-ZnO-Al transducer, the voltage VISHE ∼ 4 μV in the Pt film is observed as a result of resonant ASP from YIG(2) to Pt in the area ∼ 170 μm. The results of frequency and magnetic field mapping of VISHE(f,H) together with reflectivity of the resonator show an obvious agreement between the positions of the voltage maxima and BAW resonance frequencies fn(H) on the (f, H) plane. At the same time a significant asymmetry of the VISHE(fn(H)) value in reference to the magnetoelastic resonance (MER) line fMER(H) position is revealed, which is explained by asymmetry of the magnetoelastic waves dispersion law