C63uNQR Measurement of Stripe Order Parameter inLa2

Abstract

We demonstrate that one can measure the charge-stripe order parameter in the hole-doped CuO2 planes of La1.875Ba0.125CuO4, La1.48Nd0.4Sr0.12CuO4 and La1.68Eu0.2Sr0.12CuO4 utilizing the wipeout effects of 63 Cu NQR. Application of the same approach to La2−xSrxCuO4 reveals the presence of similar stripe order for the entire underdoped superconducting regime The mechanism of high T c superconductivity has been a major controversy throughout the past decade [1][2][3]. The complexity of the phase diagram for temperature T and hole concentration x makes it difficult to identify the key leading toward the superconducting mechanism. In 1995, Tranquada et al. [4-6] demonstrated that La 1.6−x Nd 0.4 Sr x CuO 4 (x ∼ 1 8 ) exhibits chargestripe order at T charge = 65 K, followed by a spinstripe order at somewhat lower temperature, T spin = 50 K. The discovery of the stripe phase [7] has added a new feature to the already complex phase diagram. Initially, some researchers speculated that the stripe order was merely a byproduct of the LTO-LTT (low temperature orthorhombic-low temperature tetragonal) structural phase transition and was extrinsic to the fundamental physics of high T c superconductivity. However, more recently, spin-stripe order was observed in La 2−x Sr x CuO 4 (x = 0.12 [8,9] , exhibits no critical divergence at the stripe transition. The origin of the elusiveness is in the glassy nature of the stripe transition [6,18,19]. In other words, the critical slowing down of spin-stripe fluctuations below T charge is more gradual than ordinary magnetic phase transitions involving only the spin degrees of freedom. As a consequence, the apparent critical temperature T spin of the spin-stripe order is lower for experimental probes with slower frequency scales, i.e. T spin = 50 K for elastic neutron scattering (

Ferromagnetic insulating state in manganites:55MnNMR study

“…The frequency dependence of the real and imaginary part of the susceptibility as well as their absolute values are indicative of the cluster glass behaviour similarly as reported by Ghivelder et al The situation may be similar to that observed in the lanthanum cuprates, where slowing down of the spin and/or charge fluctuations results in a strong peak in the spinlattice relaxation for the La nuclei and in a loss of signal on the Cu nuclei and it is ascribed to the glassy magnetic state [23][24][25]. It is interesting that for both Cu and La signals stretched exponential like spin-echo decay is observed in the slow fluctuation limit similarly to the one for FMI signals in manganites, while in the motionally narrowed limit, below a transition temperature T charge , corresponding to the localization of charge-ordered stripes, a Lorentzian single-exponential spin-echo decay is detected [24,26,27]. …”

Similar glassy features in theL139aNMR response of pure and disorderedLa1.88Mitrović1, Julien2, Vaulx3 et al. 2008Phys. Rev. B8211980View full textAdd to dashboardCite

“…Since 17 O and 63,65 Cu NMR signals undergo a significant wipeout below ∼50 K [19,32], it is difficult to know whether the inhomogeneity probed in 139 La T 1 measurements below ∼60 K is distinct from the one probed at higher temperatures and attributed to spatial variation of the hole concentration. At any given temperature below ∼20 K, the difference in 139 T −1 1 values between x = 0.12 and x = 0.10 samples exceeds an order of magnitude.…”

Charge-density-wave ordering in the stripe phase of underdoped cuprates

“…There is clear evidence for charge stripe [2] formation in SC La 1.6-x Nd 0.4 Sr x CuO 4 (Nd-doped LSCO) [3][4][5][6] and YBCO [7][8][9][10]. There are also strong indications that stripes exist in SC Bi2212 [11,12].…”

“…Thus, if measurements in cuprates show the presence of quasi-1D charge stripes [3][4][5][6][7][8][9][10][11][12][13], it is absolutely logic to compare transport properties of cuprates with similar properties of quasi-1D metals. Most of the non-CDW quasi-1D metals are organic.…”