Collisional Quantum Interference on Rotational Energy Transfer： Relation Between Integral Interference Angle and Rotational Quantum Number in Na2（A^1∑u^＋,ν=8～b^3∏0u,ν=14）-Na System

Collisional quantum interference （CQI） on rotational energy transfer was observed in Na2（A^1∑u^＋,ν=8～b^3∏0u,ν=14） system in collision with Na [Chem. Phys. Lett. 318 （2000） 107], and the degree of the interference was measured. The integral interference angle was obtaJned through theoretical calculation. We will research the factors that have effect on collisional quantum interference on rotational energy transfer in Na2（A^1∑u^＋,ν=8～b^3∏0u,ν=14）-Na system. Basing on the time-dependent first order Born approximation, and taking into account the anlsotroplc Lennard Jones interaction potentials and ＂straight-line＂ trajectory approximation, we obtain the factors that have effect on CQI in Na2-Na system, and obtain the relation between the integral interference angle and rotational quantum number.     

一种LED用红色荧光粉BaZn2(BO3)2：Eu3+的合成与发光性能研究

通过高温固相法制得双峰可调节本征半导体发光BaZn₂（BO₃）₂：Eu³⁺荧光粉,此类荧光粉在300~400 nm的紫外波段有很强的吸收。在375 nm的紫外光激发下,该荧光粉产生了两个宽带的发射峰,分别位于550 nm和615 nm处。并且,在395 nm的紫光激发下,荧光粉会由于Eu³⁺离子的⁵D₀→⁷F₂电偶极跃迁产生一个位于615 nm的强宽发射峰,这表明Eu³⁺离子占据了反演对称中心的位置,取代了BaZn₂（BO₃）₂中部分的Ba²⁺离子。当Eu³⁺的摩尔分数达到10%时,发生浓度猝灭。在不同浓度的Eu³⁺离子的掺杂下,BaZn₂（BO₃）₂：Eu³⁺荧光粉的发光从黄色延伸到红色,实现了荧光粉的色度可调。     

无限深量子阱中强耦合极化子的基态结合能

研究了无限深量子阱中极化子的基态性质,采用线性组合算符和变分相结合的方法导出了强耦合极化子的振动频率λ、基态能量E₀和基态结合能E_b,讨论了阱宽L和电子-LO声子耦合强度α对强耦合极化子的振动频率λ、基态能量E₀和基态结合能E_b的影响。通过数值计算,结果表明:强耦合极化子的振动频率和基态结合能随阱宽L的增大而减小,随电子-LO声子耦合强度α的增强而增大;基态能量随阱宽L的增大而减小,其绝对值随电子-LO声子耦合强度α的增强而增大;当量子阱阱宽L趋近于无限大和无限小两种极限情况下,分别与三维和二维极化子的结果相一致。     

Gd1-xEuxAl3(BO3)4纳米晶的合成及其发光性能

以高温固相反应法合成了Gd_1-xEu_xAl₃(BO₃)₄:Eu³⁺纳米荧光粉。使用XRD分析确定了样品的物相,并根据谢乐公式计算出其微晶的纳米粒度。采用了“粉末悬浮法”以甘油为分散介质,在RF540荧光光度计上测试了纳米晶荧光粉的激发光谱和发射光谱。GdAl₃(BO₃)₄基质本身发光,GdAl₃(BO₃)₄:Eu纳米荧光粉表现了Eu³⁺的特征发射光谱,其中最强峰为⁵D₀→⁷F₂发射,表明晶体结构中没有对称中心格位。实验表明在GdAl₃(BO₃)₄:Eu纳米晶荧光粉中,存在Gd³⁺对Eu³⁺发光的基质敏化作用。     

Long-distance super-exchange and quantum magnetic relaxation in a hybrid metal–organic framework

The hybrid metal–organic framework [(CH3)2NH2]Fe(HCOO)3with a perovskite-like structure exhibits a variety of unusual magnetic behaviors at low temperatures. While the long-distance super-exchange through the Fe-O–CH-O–Fe exchange path leads to a canted antiferromagnetic ordering at TN～ 19 K, a second transition of magnetic blocking develops at TB～ 9 K. The stair-shaped magnetization hysteresis loops below TBresemble the behaviors of resonant quantum tunneling of magnetization in single-molecular quantum magnets. Moreover, the magnetic relaxation also exhibits several features of resonant quantum relaxation, such as the exponential law with a single characteristic relaxation time, and the nonmonotonic dependence of relaxation rate on the applied magnetic field with a much faster relaxation around the resonant fields. The origin of quantum tunneling behaviors in the [(CH3)2NH2]Fe(HCOO)3metal–organic framework is discussed in terms of magnetic phase separation due to the modification of hydrogen bonding on the long-distance super-exchange interaction.     

含手性膦配体3-MBPA的铂(Ⅱ)配合物的2D NMR研究

利用一维和二维NMR技术,对含有手性膦配体的铂配合物trans-[Pt(3-MBPAH)₂Cl₂](1)和trans-(Pt(3-MBPA)(3-MBPAH)Cl)(2)进行¹H和¹³C NMR谱分析,否定了化合物(2)的结构为trans-[Pt(3-MBPA)₂]的可能,归属了所有的¹H和¹³C NMR谱线,并根据磷和铂及磷与磷的偶合常数确定它们是反式构型.     

库仑场对抛物量子点中强耦合极化子性质的影响

采用线性组合算符和幺正变换方法研究了在库仑场束缚下抛物量子点中强耦合束缚极化子的振动频率和基态能量。并对其进行了数值计算,结果表明:强耦合束缚极化子的振动频率和基态能量随量子点的有效受限长度的增加而减小,随电子-LO声子耦合强度的增加而增加,束缚极化子的基态能量随库仑势的增加而减小。     

Steganalysis and improvement of a quantum steganography protocol via GHZ4 state

Quantum steganography that utilizes quantum mechanical effect to achieve the purpose of information hiding is a popular topic of quantum information. Recently, El Allati et al. proposed a new quantum steganography using GHZ₄ state. Since all of the 8 groups of unitary transformations used in the secret message encoding rule change the GHZ₄ state into 6 instead of 8 different quantum states when the global phase is not considered, we point out that a 2-bit instead of a 3-bit secret message can be encoded by one group of the given unitary transformations. To encode a 3-bit secret message by performing a group of unitary transformations on the GHZ₄ state, we give another 8 groups of unitary transformations that can change the GHZ₄ state into 8 different quantum states. Due to the symmetry of the GHZ₄ state, all the possible 16 groups of unitary transformations change the GHZ₄ state into 8 different quantum states, so the improved protocol achieves a high efficiency.     

Instantons and the chiral phase transition

We examine the role of instantons in the zero-temperature chiral phase transition in an SU(N) gauge theory. For a range of N_f (the number of fermion flavors) depending on N, the theory exhibits an infrared fixed point at coupling _*. As N_f decreases, _* increases, and it eventually exceeds a critical value sufficient to trigger chiral symmetry breaking. For the case N = 2, we estimate the critical values of N_f and _* due to instantons by numerically solving a gap equation with an instanton-generated kernel. We find instanton effects of strength comparable to that of gluon exchange.     

真空紫外光激发下Ce3+、Tb3+激活的BaCa2(BO3)2的发光性质

利用XRD、VUV及UV光谱等方法对Ce³⁺、Tb³⁺离子掺杂以及Ce³⁺、Tb³⁺离子共掺的3种BaCa₂(BO₃)₂荧光粉的相纯度、发光性质、浓度猝灭现象进行研究。结果表明:3种荧光粉在VUV波段有较好的吸收,基质吸收带位于140～190 nm范围。Ce³⁺在BaCa₂(BO₃)₂的最低4f5d跃迁带位置在360 nm附近,其5d→²F_J(J=5/2, 7/2)发射峰分别位于393,424 nm。Tb³⁺掺杂的样品在172 nm激发下的发射光谱由4个窄带组成,分别对应⁵D₄→⁷F_J(J=3,4,5,6)的跃迁,其中占主导位置的是⁵D₄→⁷F₅的跃迁,大约位于543 nm处,主要为绿光发射。在Ce³⁺,Tb³⁺离子共掺杂的BaCa₂(BO₃)₂光谱中,观察到Ce³⁺-Tb³⁺离子间有能量传递。     

Macroscopic Quantum Coherence in Antiferromagnetic Molecular Magnets

The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model.On the basis of instanton technique in the spin-coherent-state path-integral representation,both the rigorous Wentzel-Kramers-Brillouin exponent and pre-exponential factor for the ground-state tunnel splitting are obtained.We find that the quantum fluctuations around the classical paths can not only induce a new quantum phase previously reported by Chiolero and Loss (Phys.Rev.Lett.80(1998)169),but also have great influence on the intensity of the ground-state tunnel splitting.Those features clearly have no analogue in the ferromagnetic molecular magnets.We suggest that they may be the universal behaviors in all antiferromagnetic molecular magnets.The analytical results are complemented by exact diagonalization calculation.     

Eu3+/Dy3+共掺Sr3Y2(BO3)4荧光粉的发光性质研究

稀土掺杂发光材料一直是科研领域研究的热点,被广泛应用于白光LED、温度传感、显示显像、新能源和激光等领域。基质的结构对于稀土离子光致发光特性有非常重要的影响,在众多发光基质材料中,硼酸盐具有透光范围宽、光学损伤阈值高、较好的热稳定性和化学稳定性等优点。碱土-稀土金属硼酸盐Sr₃Y₂(BO₃)₄具有出色的光学性能,对其发光性能的研究具有重要意义。稀土离子Eu3+具4f6电子层,是一种典型的下转换发光中心离子,常被选作红色发光材料的激活剂。Dy3+具4f9电子层,也是一种典型的下转换发光中心离子,在紫外光激发下,在蓝色光区和橙色光区有较强的荧光发射。采用高温固相法合成了Sr₃Y₂(BO₃)₄∶Eu3+/Dy3+荧光粉,通过XRD和SEM对样品的结构和形貌进行了表征,XRD结果表明,1 000 ℃烧结5 h,H₃BO₃过量20%为最佳制备条件,且少量的Eu3+和Dy3+掺杂并未改变Sr₃Y₂(BO₃)₄的晶格结构。SEM图像表明Sr₃Y₂(BO₃)₄基质的平均晶粒尺寸为2～4 μm,10%Eu3+单掺和5%Eu3+/5%Dy3+双掺样品与基质Sr₃Y₂(BO₃)₄的SEM图像相比,形貌和尺寸并没有发生明显的改变。Sr₃Y₂(BO₃)₄∶Eu3+荧光粉的发光结果表明,分别在395和466 nm激发下,浓度为5%,10%和15%的Eu3+单掺Sr₃Y₂(BO₃)₄荧光粉的主要发光位于593和613 nm的红光发射,峰强度随着Eu3+浓度的增加呈现先增加后降低的变化形式,掺杂浓度为10%时发光强度最大,说明存在浓度猝灭现象。色坐标结果显示,激发波长由395 nm变化到466 nm,Sr₃Y₂(BO₃)₄∶Eu3+荧光粉的发光颜色从橙红色向红色转变。引入Dy3+后,Sr₃Y₂(BO₃)₄∶Eu3+/Dy3+样品的发射光谱出现Dy3+的486 nm的蓝光发射（4F_9/2→6H_15/2）和576 nm的橙光发射（4F_9/2→6H_13/2）,并且随着Dy3+浓度的增加,对Eu3+的5D₀→7F_{1, 2, 3, 4}跃迁有抑制作用。色坐标结果显示通过调整掺杂离子Eu3+和Dy3+的比例可实现Sr₃Y₂(BO₃)₄∶Eu3+/Dy3+荧光粉的颜色从红色区域向橙色区域转变,说明其在显示方面具有良好的应用前景。     

具有Dzyaloshinskii-Moriya相互作用的XY模型的量子相干性

研究了具有Dzyaloshinskii-Moriya(DM)相互作用的一维横场XY自旋链的量子相变和量子相干性.采用约旦-维格纳变换严格求解了哈密顿量,并描绘了体系的关联函数和相图,相图包含反铁磁相、顺磁相和螺旋相.利用相对熵和Jensen-Shannon熵讨论了XY模型的量子相干性.研究发现,相对熵与Jensen-Shannon熵所表现的行为都可以很好地表征该模型的量子相变.非螺旋相中量子相干性不依赖DM相互作用,而在螺旋相DM相互作用对量子相干性有显著影响.此外,指出了在带有DM相互作用的这一类反射对称破缺体系中关联函数计算的常见问题.     

NaZnLa(PO4)2中Ce3+和Tb3+的发光

采用高温固相反应合成了NaZnLa(PO₄)₂中掺杂Ce³⁺、Tb³⁺的荧光体,对其晶体结构、发光行为进行了研究,并尝试对NaZnLa(PO₄)₂:Ce,Tb荧光体进行调制。NaZnLa(PO₄)₂是LaPO₄的同构物,为单斜晶系独居石结构,从XRD谱数据得到NaZnLa(PO₄)₂基质的晶胞参数为a=0.6823nm,b=0.7045nm,c=0.6497nm,β=1039°,v=0.303nm³,其晶胞参数与单斜LaPO₄的晶胞参数相似。在NaZnLa(PO₄)₂:Ce,Tb荧光体中,Ce³⁺对Tb³⁺有良好的敏化作用,掺杂适量的BO₃^3-、Al³⁺、Dy³⁺,可以增强发光亮度。     

Probabilistic quantum teleportation of shared quantum secret

Very recently, Lee et al. proposed a secure quantum teleportation protocol to transfer shared quantum secret between multiple parties in a network[Phys. Rev. Lett. 124 060501 (2020)]. This quantum network is encoded with a maximally entangled GHZ state. In this paper, we consider a partially entangled GHZ state as the entanglement channel, where it can achieve, probabilistically, unity fidelity transfer of the state. Two kinds of strategies are given. One arises when an auxiliary particle is introduced and a general evolution at any receiver's location is then adopted. The other one involves performing a single generalized Bell-state measurement at the location of any sender. This could allow the receivers to recover the transmitted state with a certain probability, in which only the local Pauli operators are performed, instead of introducing an auxiliary particle. In addition, the successful probability is provided, which is determined by the degree of entanglement of the partially multipartite entangled state. Moreover, the proposed protocol is robust against the bit and phase flip noise.     

Ca3La(BO3)3：Tb3+的合成与发光性质

高温固相反应法合成了Ca₃La(BO₃)₃:Tb³⁺光致发光材料。利用扫描电镜和激光衍射分析仪测定了样品的晶粒形貌及粒径大小分布,利用荧光分光光度计研究了Ca₃La(BO₃)₃:Tb³⁺的光致发光特性。确定了在Ca₃La(BO₃)₃基质中Tb³⁺离子浓度对其发光强度的影响及其自身浓度猝灭机理;探讨了助熔剂Li₂CO₃、敏化剂Ce³⁺离子的加入对荧光粉发光强度的影响。     

Quantum oscillations and nontrivial transport in(Bi_(0.92)In_(0.08))_2Se_3

Quantum phase transition in topological insulators has drawn heightened attention in condensed matter physics and future device applications.Here we report the magnetotransport properties of single crystalline(Bi_(0.92)In_(0.08))_2Se_3.The average mobility of～1000 cm~2·V~(-1)·s~(-1)is obtained from the Lorentz law at the low field(3 T)up to 50 K.The quantum oscillations rise at a field of～5 T,revealing a high mobility of～1.4×10~4cm~2·V~(-1)·s~(-1)at 2 K.The Dirac surface state is evident by the nontrivial Berry phase in the Landau–Fan diagram.The properties make the(Bi_(0.92)In_(0.08))_2Se_3a promising platform for the investigation of quantum phase transition in topological insulators.     

铁基超导体的量子临界行为

铁基超导体呈现丰富的电子相图, 各种有序态相互交叠. 本文主要介绍利用核磁共振手段在空穴型和电子型掺杂的BaFe₂As₂以及LaFeAsO_1-xF_x这三种具有代表性的铁基超导体中探测到的反铁磁序与超导序的微观共存、量子临界点和量子临界行为. 实验发现, 无论在空穴型还是电子型掺杂的铁基超导体中, 反铁磁相变温度都随着掺杂被抑制, 并最终在某个掺杂量降到零温而形成量子临界点. 在反铁磁转变温度之上存在结构相变, 其转变温度也随着掺杂而降低. 核磁共振谱证实结构相变也形成一个量子临界点. 本文介绍核磁共振及输运测量揭示的这两种量子临界点附近存在的量子临界行为, 共存态下奇异的超导性质等.     

压力下碱金属铁硒基超导体中的现象与物理

在凝聚态物理研究中, 压力作为对物质状态调控的独立变量得到了广泛的应用. 压力对发现物质的新现象、新规律及对其形成机理的理解和对相关理论的验证起到了重要的作用, 尤其在超导电性的研究中取得了巨大的成功. 文章简要的介绍了通过利用压力手段对具有相分离结构的碱金属铁硒基超导体A_xFe_2-ySe₂ (A=K, Rb, Tl/Rb)开展的系列研究所取得的实验结果, 以及其他一些文献中报道的在此方面的主要实验与理论研究工作, 包括压力导致的超导再进入现象和其产生的量子临界机理、其特有的反铁磁绝缘体相在该类超导体实现超导电性中的作用、化学负压力对超导电性的影响、构成该类超导体的反铁磁序与其寄居的超晶格的关系等.