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Zhihao GengShiping Feng 《Physics letters. A》2011,375(37):3329-3334
The electronic Raman response in the electron-doped cuprate superconductors is studied based on the t-t′-J model. It is shown that although the domelike shape of the doping dependent peak energy in the B2g symmetry is a common feature for both electron-doped and hole-doped cuprate superconductors, there are pronounced deviations from a cubic response in the B1g channel and a linear response in the B2g channel for the electron-doped case in the low energies. It is also shown that these pronounced deviations are mainly caused by a nonmonotonic d-wave gap in the electron-doped cuprate superconductors. 相似文献
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Zhihao Geng 《Physics letters. A》2010,375(2):214-219
The doping and temperature dependence of the electronic Raman response in cuprate superconductors is studied within the kinetic energy driven superconducting mechanism. It is shown that the temperature dependent depletion at low-energy shifts is faster in the B1g symmetry than in the B2g symmetry. In analogy to the domelike shape of the doping dependent superconducting transition temperature, the maximal peak energy in the B2g channel occurs around the optimal doping, and then decreases in both underdoped and overdoped regimes. Moreover, the overall density of Cooper pairs increases with increasing doping in the underdoped regime. 相似文献
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By considering the nonmonotonic d-wave gap effect, the energy and momentum dependence of quasiparticle scattering interference is studied in the presence of a single impurity. It is shown that the pattern of the quasiparticle scattering peaks in the full Brillouin zone of electron-doped cuprate superconductors is very different from that in the hole-doped case described by the Octet model. This difference is the result of the nonmonotonic d-wave superconducting gap in the electron-doped case. As the energy increases, the position of the local peaks in the Brillouin zone moves rapidly. In particular, the characteristic peaks of the electron-doped cuprate superconductors appear between the antinodal and nodal directions, unlike in the hole-doped case. 相似文献
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电子拉曼实验表明在空穴型掺杂的铜氧化物超导体中存在两能隙行为,即在欠掺杂区,随着掺杂浓度的降低,一个能隙逐渐增大而且在超导转变温度以上仍然存在,而另一个能隙逐渐减小且在DDW态依然存在.解释两能隙行为非常重要因为它与赝能隙的机理密切相关.本文计算了超导序和d-density-wave(DDW)序竞争机理下相图上不同区域的电子拉曼谱,发现欠掺杂区能隙表现出两能隙行为,与实验一致.特别地,本文发现B1g峰对应能量由超导和DDW序共同决定,且随着掺杂浓度的降低而增大,在D
关键词:
两能隙
电子拉曼散射
竞争序 相似文献
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Zhi Wang 《Physics letters. A》2010,374(30):3084-3091
The quasiparticle scattering interference phenomenon characterized by the peaks in the local density of states is studied within the kinetic energy driven superconducting mechanism in the presence of a single impurity. By calculation of the Fourier transformed ratio of the local density of states at opposite energy, it is shown that the quasiparticle scattering interference phenomenon can be described qualitatively by a single impurity in the kinetic energy driven homogeneous d-wave superconducting state. The amplitude of the peak increases with increasing energy at the low energy, and reaches a maximum at the intermediate energy, then diminishes to zero at the high energy. The theory also predicts that with increasing doping, the position of the peak along the nodal direction moves towards to the center of the Brillouin zone, while the position of the peak along the antinodal direction is shifted to large momentum region. 相似文献
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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LaFeAsO1-xFx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. 相似文献
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The interplay between the superconducting gap and normal-state pseudogap in the bilayer cuprate superconductors is studied based on the kinetic energy driven superconducting mechanism. It is shown that the charge carrier interaction directly from the interlayer coherent hopping in the kinetic energy by exchanging spin excitations does not provide the contribution to the normal-state pseudogap in the particle–hole channel and superconducting gap in the particle–particle channel, while only the charge carrier interaction directly from the intralayer hopping in the kinetic energy by exchanging spin excitations induces the normal-state pseudogap in the particle–hole channel and superconducting gap in the particle–particle channel, and then the two-gap behavior is a universal feature for the single layer and bilayer cuprate superconductors. 相似文献
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F. Galluzzi 《Il Nuovo Cimento D》1985,5(1):100-110
Summary A unifying approach to the theory of Raman intensities including nonadiabatic coupling and vibronic coupling is presented
and explicit equations of the resonant scattering tensor are obtained for weak vibronic coupling. Previous results reported
in the literature are derived as special cases of the present treatment.
Riassunto Si presenta un trattamento teorico delle intensità Raman comprendente sia l'accoppiamento non adiabatico che quello vibronico e si riportano le equazioni esplicite per il tensore di scattering risonante nel caso di accoppiamento vibronico debole. Vari risultati presentati in letteratura sono derivati come casi speciali di questo approccio unificante.
Резюме Предлагается унифицировать подход к теоретическому описанию рамановских интенсивностей, включая неадиабатическую связь и колебательную связь. В случае слабой колебательной связи получаются точные уравнения для тензора резонансного рассеяния. Различные результаты опубликованные в литературе, получаются как частные случаи предложенного унифицированного подхода.相似文献
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Evolution of the 128-cm-1 Raman phonon mode with temperature in Ba(Fe1-xCox)2As 2 (x = 0.065 and 0.2) 下载免费PDF全文
We report electronic Raman scattering measurements on Ba(Fei1-xCox)2As2(x = 0.065 and 0.2) single crystals with Raman shifts from 9 cm-1 up to 600 cm-1 in the symmetry of Blg with respect to 1 Fe unit cell.When the crystals are cooled down,the evident quasielastic peaks of Raman spectra occur only in the crystal with x = 0.065,which is due to the contribution of orbital ordering between xz and yz Fe 3d orbitals,as we reported in another work.Here,we analyze the Eg phonon at 128 cm-1,which has the same function form of its Raman tensors as those of xz and yz Fe 3d orbitals in these two crystals respectively.Unlike their electronic continuums,no anomalies are found in the Eg phonons of these two samples,which simply follows the expressions corresponding to the anharmonic phonon decay into acoustic phonons with the same frequencies and opposite momenta.Our results indicate that the structural and magnetic phase transition might be completely suppressed by chemical doping and there is not any indication of coupling between charge nematicity and Eg phonon mode from our experimental results,which is consistent with the results in our previous work. 相似文献
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采用基于第一性原理的平面波赝势方法,计算了铁基氟化物及其钴掺杂超导体SrFe1-xCoxAsF(x=0,0.125)在四方非磁态与正交条纹反铁磁态下的声子谱(声子色散曲线、声子态密度)及电-声子耦合常数.计算发现:条纹反铁磁相互作用下的自旋-声子耦合效应强于电-声子耦合作用使声子谱的宽度减小;自旋效应使声子的有效质量增加导致条纹反铁磁态下Fe原子与As原子的耦合振动频率减小.另外,掺杂和自旋效应是提高电-声子耦合常数的两个有效方法,但计算所得超导转变温度远小于实验测量值,表明铁基超导电性非简单的电-声子耦合配对机理. 相似文献
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Summary By nonlinear mixing of IR and visible radiation,i.e. coherent Raman scattering by polaritons driven by a CO2 laser, it has been possible to get high-resolution spectra for theF-modes of a NaClO3 crystal in the region (907÷957) cm−1, where several isotopic modes are present. The obtained independent measurement of the refractive index and absorbance allows
an accurate determination of the polariton dispersion curve and its width inq-space. The experimental data confirm the existence of a localized isotopic mode at 931 cm−1 and a strongly damped isotopic mode near 960 cm−1. Finally, an accurate measurement of the dispersion of the second-order nonlinear polarizability in the same energy region
has been obtained for the first time.
This work was supported by the Italian Consiglio Nazionale delle Ricerche and Ministero della Pubblica Istruzione. 相似文献
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Summary Nonlinear mixing of IR and visible radiation,i.e. coherent Raman scattering by polaritons driven by a CO2 laser, has been used to obtain the dispersion curve and its width inq-space of the polariton associated to theE-phonon at 1065 cm−1 in crystal quartz. It is shown in this paper that a direct method to determine indipendently, with high precision, the refractive
index and absorbance of a crystal can be obtained in this way. The results are compared with accurate data obtained from Raman
scattering by polaritions in thermal equilibrium and very good agreement is found between the two measurements. It is finally
shown that nonlinear-mixing techniques turn out to be completely consistent with the simple picture of scattering of light
by hot polaritons.
This work was supported by the Italian Consiglio Nazionale delle Ricerche del Ministero della Pubblica Istruzione. 相似文献
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Both the oxygen content and Tonset c of the Bi2Ca2.5(Ln, Ln+)0.5Cu2O y system monotonically increases as the mean ionic radius of (Ln, Ln+) increases. The structural modulations in all of the samples are almost commensurate with a period equal to 9b. In Bi2-xPbCa2.5Nd0.5Cu2O y , Tonset c decreases with increasing Pb concentration. In order to investigate the effect of post annealing using a hot isostatic press (HIP), Bi2Ca2.5La0.25Pr0.25Cu2O y was processed under different HIP conditions. This result suggested that HIP annealing causes a phase change from the 232 structure to the 221 structure. 相似文献
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In this work,Raman scattering measurements have been performed on the collapsed phase CaCo_2As_2 crystals.At least 8 Raman modes were observed at room temperature though CaCo_2As_2 is structurally similar to other 122 compounds like BaFe_2As_2.Two Raman modes are assigned to the intrinsic A_(1g)and B_(1g)of this material system respectively.The other ones are considered to originate from the local vibrations relevant to cobalt vacancies.Careful polarized measurements allow us to clearly resolve the four-fold symmetry of the B_(1g)mode,which put strong constraints on possible point group symmetries of the system with Co vacancies.The temperature-dependent measurements demonstrate that the anomalies in both frequency and width of the B_(1g)mode occur around Neel temperature T_N.The anomalies are considered to be related to the gap opening near the magnetic transition.The study may shed light on the structural and magnetic changes and their correlations with superconductivity in 122 systems. 相似文献