【作者】 赵越；

【导师】 柏利慧；

【作者基本信息】 山东大学 ， 凝聚态物理， 2024， 博士

【摘要】 腔磁子学作为一个新兴的领域,主要研究磁振子与微波光子之间的相互作用。磁振子和微波光子都可以作为量子信息的载体,在量子信息技术中具有潜在的应用价值。磁振子具有易调谐、带宽大、兼容性好等优势;它的激发和传播不需要运动电荷参与,因此能有效避免焦耳热的产生。这些优势对于提升信息处理器件的性能和使用寿命至关重要。相较于磁振子,微波光子则具有传播速度快、抗干扰性强以及可集成度高等优势。基于磁振子与微波光子相互作用构造的磁振子-微波光子耦合系统兼备两者的优势。对于磁振子-微波光子耦合系统进行探测和调控,能够实现对相干信息的处理,有望对光子学、量子信息科学以及自旋电子学等领域的发展产生重要的促进作用。经过大量的理论和实验研究,人们发展出包括微波传输、布里渊散射、自旋泵浦输运在内的多种探测磁振子-微波光子耦合系统的技术,实现了对耦合系统中微波光子的强度和相位、磁振子强度信息的读取,揭示了磁振子-微波光子耦合系统中的耗散耦合、奇异点、电磁非互易异以及非线性等诸多新颖现象,拓宽了磁振子-微波光子耦合系统的研究范围。然而,目前仍然缺乏一种能够直接探测磁振子-微波光子耦合系统中磁振子相位信息的方式。此外,磁振子-微波光子耦合系统的调控方式,例如改变自旋数目、调整谐振腔的结构等,不能在同一个耦合系统中进行。因此,发展一种对磁振子相位敏感的探测方式,并探索在单一磁振子-微波光子耦合系统中的多维调控技术,对于发展基于磁振子-微波光子耦合系统的应用技术具有重要意义。本文基于纳米尺度坡莫合金(Py)-超导谐振腔以及钇铁石榴石/钆镓石榴石(YIG/GGG)-超导谐振腔耦合系统,揭示了自旋整流电压与磁振子相位之间的关系,实现了对耦合系统中磁振子相位的直接探测,并发展了多维度调控磁振子-微波光子耦合系统的新技术。本文的主要内容如下:(1)利用自旋整流效应,发展了一种电学探测耦合系统中磁振子相位的新技术,从而实现了对耦合系统中磁振子和微波光子信息的完整探测。我们制备了高品质的高温超导谐振腔,实现了超导谐振腔与纳米厚度Py薄膜的耦合,并利用自旋整流技术对耦合系统进行探测,进而揭示了自旋整流电压和耦合系统中磁振子相位之间的关系。当固定外加磁场扫描微波的频率时,我们发现自旋整流电压为负值时,磁振子和微波的电流之间以同相位振荡;自旋整流电压为正值时,磁振子和微波电流之间振荡相位相差180°。这一特性使得直接探测磁振子相位成为可能,拓宽了耦合系统探测的维度。此外,我们发现当外加微波频率等于谐振腔的共振频率时,自旋整流电压信号的振幅呈现出最大值,与固定外加磁场扫描微波频率时,微波透射曲线在耦合磁场处呈现出最小值不同,这表明自旋整流效应在探测低协同率耦合系统时具有较高的灵敏性。我们还采用自旋整流效应表征了 Py-超导谐振腔耦合系统中色散和半宽曲线的耦合特征,这为从磁振子角度对耦合系统进行探测提供了更多的手段。(2)利用直流电流,实现了对坡莫合金/铂(Py/Pt)-超导谐振腔耦合系统中Purcell效应的电学调控,这为集成化磁振子-微波光子耦合系统的实际应用创造了条件。通过理论分析,我们证实了在Purcell耦合区域中通过改变磁振子或谐振腔的耗散率能够实现对耦合系统的调控。通过在Py/Pt双层膜中施加直流电流,我们测量了不同直流电流下Py/Pt-超导谐振腔耦合系统的微波透射图谱,提取了不同电流下耦合系统的色散和半宽曲线,并定义了描述Purcell区域耦合特征的物理量2g’和δ(Δω)。我们观察到随着电流增大2g’和δ(Δω)逐渐增大,这意味着通过施加直流电流实现了对Purcell效应的调控。我们揭示了2g’和δ(Δω)随电流变化的物理机制,并确定了磁振子耗散率在耦合调控中的重要作用。此外,通过获取2g’和δ(Δω)的数值,我们建立了一套从色散和半宽的角度直接获取Purcell效应耦合强度的方法。(3)利用具有高品质因子的高温超导谐振腔,实现了 YIG/GGG薄膜(自旋数目约为5.28× 1015)与超导谐振腔之间的强相干耦合,并观察到色散曲线的反交叉现象。在YIG/GGG-超导谐振腔耦合系统中,我们探究了 YIG/GGG薄膜以及超导谐振腔的耗散率对温度的依赖性,随着温度降低YIG/GGG和超导谐振腔的耗散率均呈现出增大的趋势。我们揭示了两个子系统中耗散率随温度变化的物理机制,指出GGG衬底磁化率对超导谐振腔的影响。通过改变温度的方式,我们实现了 YIG/GGG-超导谐振腔耦合系统在强耦合、Purcell、以及弱耦合区域的连续转变,并实现了对耦合系统中协同率的连续调节。更多还原

【Abstract】 Cavity magnonics,as an emerging field,focuses on the interaction between magnons and microwave photons.Both magnons and microwave photons serve as carriers of quantum information,holding promising potential for applications in quantum information technology.Magnons have the advantages of tunability,broad bandwidth,and compatibility.The excitation and propagation of the magnon do not involve moving charges,thus effectively avoiding the Joule heating effect,which is crucial for enhancing the performance and lifetime of information processing devices.In comparison,microwave photons exhibit advantages such as rapid propagation,high interference immunity,and high integrability.Based on the interaction between magnons and microwave photons,the magnon-microwave photon coupled system combines the advantages of both.The detection and modulation of magnon-microwave photon systems enable coherent information processing,which is expected to play an important role in the fields of photonics,quantum information science,and spintronics.In recent years,the researchers have developed lots of techniques for probing the magnon-microwave photon coupling system,including microwave transmission,Brillouin scattering,and spin-pumping,and have realized the reading of the magnitude and phase of the microwave photon subsystem and the magnitude information of the magnon subsystem in the coupled system,and revealed many novel phenomena,such as dissipative coupling,the exceptional point,electromagnetic nonreciprocal,and nonlinearity,etc.,in the magnon-microwave photon coupling system,and broadens the scope of the study of the magnon-microwave photon coupling system.However,direct detection of the magnon phase remains challenging until now.In addition,the modulation of the magnon-microwave photon coupling system,such as changing the number of spins and adjusting the structure of the resonant cavity,cannot be performed in the single coupling system.Therefore,it is important to develop a detection method sensitive to the magnon phase as well as a multidimensional modulation technique in a single magnon-microwave photon system,which is important for the development of technologies based on magnon-microwave photon systems.In this paper,based on the Py-superconducting cavity and YIG/GGG-superconducting cavity system,we studied the relationship between the spin rectification voltage and the phase of the magnon,realizing the direct detection of the phase of magnon in the coupled system.Further,we proposed new technology for multidimensional modulation of the magnonmicrowave photon coupling system.The main contents of this paper are as follows:(1)We realized the direct detection of the magnon phase in a coupled system by using spin rectification measurements,thus realizing the electrical detection of magnon and microwave photon information in a coupled system.Specifically,we fabricated a high-quality superconducting cavity and realized the coupling of the superconducting cavity to a nanothickness Py film.By measuring the spin rectification effect in the Py layer,we found the relationship between the sign of the spin rectification voltage(VSR)and the phase of the magnon in the coupled system.We found that the VSR is negative for the low-frequency coupled mode,meaning the relative phase between the magnon and the microwave current is in-phase;And the VSR is positive for the high-frequency coupled mode,meaning the relative phase between the magnon and the microwave current is out-of-phase.Our results make it possible to directly detect the phase of the magnon in the coupling system and broaden the dimensions of detecting the coupling system.Moreover,when the microwave frequency is equal to the resonance frequency of the superconducting cavity,we found that the amplitude of the spin rectification voltage exhibits a maximum value;unlike the microwave transmission curve that exhibits a minimum value,which indicates that spin rectification effect is more sensitive to probe the coupled system with low cooperative.And,we also investigated the coupling characteristics of the dispersion and linewidth curves in the Py-superconducting cavity coupled system using spin rectification,which provides further means of probing the coupling system from the magnon subsystem.(2)By using a direct current,we realized the electrical modulation of the Purcell effect in the Py/Pt-superconducting cavity system,which offers the possibility of the application.Through theoretical analysis,we confirmed that the modulation of the coupled system is realized by electrically changing the dissipation rate of the magnon or photon in the Purcell coupling regime.By measuring the microwave transmission curve of the Py/Ptsuperconducting cavity coupled system under different direct currents and extracting the dispersion and linewidth curves of the coupled system under different direct currents.We observed that 2g’ and δ(Δω)gradually increase with increasing direct current,which indicates that the modulation of the Purcell effect is realized by applying a direct current.We found the mechanism of the variation of 2g’ and δ(Δω)with current,and proposed the important role for magnon dissipation rate in controlling the coupled system.In addition,by obtaining the values of 2g’ and δ(Δω),we have established a method to directly obtain the coupling strength of the Purcell regime from the perspective of dispersion and linewidth.(3)Using a high-quality superconducting cavity,we realized a strong coupling between a YIG/GGG thin film(with a spin number of about 5.28 × 1015)and a superconducting cavity,and we observed an anti-crossing dispersion curve.In the YIG/GGG-superconducting cavity coupled system,we investigated the temperature dependence of the dissipation rate of the YIG/GGG film and the superconducting cavity.We found the dissipation rates of YIG/GGG and superconducting cavities show an increasing trend with the decreasing temperature,which may be attributed to the magnetization of the GGG substrate.By varying the temperature,we realized the continuous transition of the YIG/GGG-superconducting cavity coupled system in the strong coupling,Purcell,and weak coupling regime,and the continuous tuning of the cooperativity in the coupled system.更多还原