اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA Comparison of Stripe Modulations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$
140
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We report combined soft and hard x-ray scattering studies of the electronic and lattice modulations associated with stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$. We find that the amplitude of both the electronic modulation of the hole density and the strain modulation of the lattice is significantly larger in La$_{1.875}$Ba$_{0.125}$CuO$_4$ than in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$ and is also better correlated. The in-plane correlation lengths are isotropic in each case; for La$_{1.875}$Ba$_{0.125}$CuO$_4$, $xi^{hole}=255pm 5$ AA whereas for La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$F, $xi^{hole}=111pm 7$ AA. We find that the modulations are temperature independent in La$_{1.875}$Ba$_{0.125}$CuO$_4$ in the low temperature tetragonal phase. In contrast, in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$, the amplitude grows smoothly from zero, beginning 13 K below the LTT phase transition. We speculate that the reduced average tilt angle in La$_{1.875}$Ba$_{0.125}$CuO$_4$ results in reduced charge localization and incoherent pinning, leading to the longer correlation length and enhanced periodic modulation amplitude.
قيم البحث
اقرأ أيضاً
Using polarized neutron scattering we establish that the magnetic order in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$ is either (i) one dimensionally modulated and collinear, consistent with the stripe model or (ii) two dimensionally modulated with a no
vel noncollinear structure. The measurements rule out a number of alternative models characterized by 2D electronic order or 1D helical spin order. The low-energy spin excitations are found to be primarily transversely polarized relative to the stripe ordered state, consistent with conventional spin waves.
A charge modulation has recently been reported in (Y,Nd)Ba$_2$Cu$_3$O$_{6+x}$ [Ghiringhelli {em et al.} Science 337, 821 (2013)]. Here we report Cu $L_3$ edge soft x-ray scattering studies comparing the lattice modulation associated with the charge m
odulation in YBa$_2$Cu$_3$O$_{6.6}$ with that associated with the well known charge and spin stripe order in La$_{1.875}$Ba$_{0.125}$CuO$_4$. We find that the correlation length in the CuO$_2$ plane is isotropic in both cases, and is $259 pm 9$ AA for La$_{1.875}$Ba$_{0.125}$CuO$_4$ and $55 pm 15$ AA for YBa$_2$Cu$_3$O$_{6.6}$. Assuming weak inter-planar correlations of the charge ordering in both compounds, we conclude that the order parameters of the lattice modulations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and YBa$_2$Cu$_3$O$_{6.6}$ are of the same order of magnitude.
We use femtosecond resonant soft x-ray scattering to measure the ultrafast optical melting of charge-order correlations in La$_{1.875}$Ba$_{0.125}$CuO$_4$. By analyzing both the energy-resolved and energy-integrated order parameter dynamics, we find
evidence of a short-lived nonequilibrium state, whose features are compatible with a sliding charge density wave coherently set in motion by the pump. This transient state exhibits shifts in both the quasielastic line energy and its wave vector, as expected from a classical Doppler effect. The wave vector change is indeed found to directly follow the pump propagation direction. These results demonstrate the existence of sliding charge order behavior in an unconventional charge density wave system and underscore the power of ultrafast optical excitation as a tool to coherently manipulate electronic condensates.
The occurrence of charge-density-wave (CDW) order in underdoped cuprates is now well established, although the precise nature of the CDW and its relationship with superconductivity is not. Theoretical proposals include contrasting ideas such as that
pairing may be driven by CDW fluctuations or that static CDWs may intertwine with a spatially-modulated superconducting wave function. We test the dynamics of CDW order in La$_{1.825}$Ba$_{0.125}$CuO$_4$ by using x-ray photon correlation spectroscopy (XPCS) at the CDW wave vector, detected resonantly at the Cu $L_3$-edge. We find that the CDW domains are strikingly static, with no evidence of significant fluctuations up to 2, icefrac{3}{4} hours. We discuss the implications of these results for some of the competing theories.
The charge and spin correlations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ (LBCO 1/8) are studied using Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS). The static charge order (CO) is observed at a wavevector of $(0.24,0)$ and its charge nature co
nfirmed by measuring the dependence of this peak on the incident x-ray polarization. The paramagnon excitation in LBCO 1/8 is then measured as it disperses through the CO wavevector. Within the experimental uncertainty no changes are observed in the paramagnon due to the static CO, and the paramagnon seems to be similar to that measured in other cuprates, which have no static CO. Given that the stripe correlation modulates both the charge and spin degrees of freedom, it is likely that subtle changes do occur in the paramagnon due to CO. Consequently, we propose that future RIXS measurements, realized with higher energy resolution and sensitivity, should be performed to test for these effects.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
