Phase diagram of charge order in La1.8−xEu0.2Sr

Abstract

Resonant soft x-ray scattering experiments with photon energies near the O K and the Cu L3 edge on the system La1.8−xEu0.2SrxCuO4 for 0.1 ≤ x ≤ 0.15 are presented. A phase diagram for stripe-like charge ordering is obtained together with information on the structural transition into the low-temperature tetragonal phase. A clear dome for the charge ordering around x = 1 8 is detected well below the structural transition. This result is quite different from other systems in which static stripes are detected. There the charge order is determined by the structural transition appearing at the same temperature. Furthermore we present results for the coherence length and the incommensurability of the stripe order as a function of Sr concentration. Later on static stripe order was also detected in the compounds La 2−x Ba x CuO 4 (LBCO) [3][4][5] and La 1.8−x Eu 0.2 Sr x CuO 4 (LESCO). 6-8In all these systems it is believed that static stripe order is stabilized by a structural transition from a low temperature orthorhombic (LTO) to a low temperature tetragonal (LTT) phase in which the CuO 6 octahedra are tilted along the [110] HT T and [100] HT T directions of the high temperature tetragonal (HTT) phase, respectively. Generally, the stripe order is accompanied by a suppression of coherent superconductivity and the amount of this suppression is increasing with increasing tilt angle Φ in the LTT phase. 9The tilt angle increases with decreasing ionic radius of substitutes on the La sites due to a chemical pressure along the CuO 2 layers. In LESCO with the small Eu ions the antiferromagnetic stripe order almost completely replaces the superconducting phase for x < ∼ 0.2. This apparent anticorrelation between stripe order and superconductivity, however, was recently questioned by the interpretation of transport data in LBCO in terms of a layer decoupled stripe superconductor with no phase coherence perpendicular to the CuO 2 layers. 10So far complete phase diagrams for the structural, the charge, and the spin order in the systems LBCO, LNSCO, and LESCO were proposed in Ref. In this Brief Report we complete our previous resonant soft x-ray scattering (RSXS) studies on the stripe like charge order in LESCO. 8While there we have reported data only for doping concentrations x ≥ 1 8 , in the present contribution we present measurements on both sides of the concentration x = 1 8 . Furthermore we present more information on the correlation length and on the incommensurability wave vector as a function of doping concentration. Finally we show an extended phase diagram for the lattice and the charge order in LESCO.Traditionally, charge order was detected by measuring superstructure reflections with x-ray or neutron scattering. Both methods were used to study stripe-like charge order in LNSCO and LBCO. 2,11,17 In the case of LESCO, only hard x-ray scattering was successful. 18RSXS at the O K and Cu L edges is a particular sensitive method to detect charge order in doped cuprates. 5,8At the prepeak of the O K edge, the form factor ...

Momentum-Dependent Charge Correlations inYBa2Cu3O6+δSuperconductors Probed by Resonant X-Ray Scattering: Evidence for Three Competing Phases

“…[28] Recent resonant [29,30] and nonresonant [31] x-ray diffraction experiments on samples in this doping regime have revealed nearly critical, biaxial charge density wave (CDW) correlations. High-field nuclear magnetic resonance (NMR) experiments [32] for δ ∼ 0.5 have been interpreted in terms of a uniaxial commensurate chargeordered state akin to the commensurate striped state observed in the 214 family for x = 1/8, [10][11][12][13][14] which is incompatible with the wavevector extracted from the x-ray arXiv:1212.5580v3 [cond-mat.supr-con] …”

“…[25,26] For δ < 0.5, uniaxial incommensurate magnetic order forms gradually upon cooling and coexists with superconductivity at low temperatures. [2,27] Unlike the well known "striped" state in the (La,Nd,Eu) 2−x (Ba,Sr) x CuO 4 (214) family, [5,[10][11][12][13][14] which encompasses both spin and charge degrees of freedom, a corresponding charge modulation has not been found in the low-doping regime of YBCO 6+δ . For δ > 0.5, on the other hand, static magnetic order disappears, and the magnetic excitation spectrum determined by neutron scattering exhibits a large spin gap.…”

“…In underdoped cuprates, however, the screening is less effective, and the role of materialsspecific disorder in the formation of the unusual spin and/or charge textures observed in this regime of the phase diagram has been a subject of long-standing debate. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Recent research on the stoichiometric underdoped compounds YBa 2 Cu 3 O 6.5 and YBa 2 Cu 4 O 8 has provided new perspectives for the resolution of the influence of disorder on the electronic phase behavior of the underdoped cuprates. In these materials, the oxygen acceptors are arranged in ordered chains rather than placed randomly in the crystal lattice, so that chemical and structural disorder is minimized.…”

Comparison of charge modulations in La1.875Ba0.125CuO4and YBaThampy1, Blanco-Canosa2, García-Fernández3 et al. 2013Phys. Rev. B415490View full textAdd to dashboardCite

“…La 2 CuO 4 with dopants substituting La (La 2−x−y (Sr,Ba) x (Eu,Nd) y CuO 4 ), have been shown to exhibit so-called stripe order near x = 1/8: that is anti-phase antiferromagnetic domains separated by stripes of uniaxial charge [1][2][3][4][5][6][7][8][9]. This ordering co-exists with, and possibly competes with superconductivity [1, 3, 6, 10, and 11].…”

Cu nuclear magnetic resonance study of charge and spin stripe order inLa1.875Ba0.125CuO4

“…Yet some issues remain unresolved, and the technique is still capable of providing fresh information on the local electronic physics in the cuprates. Recently, charge and spin stripe order has emerged as one of the crucial ingredients of the cuprate phenomenology [1][2][3][4][5][6][7] , and NMR in these ordered phases has once more come into focus. In the yttrium-123 (YBCO) family, copper NMR has provided direct evidence of a commensurate charge stripe ordering at high magnetic fields [8][9][10] , while lanthanum NMR in the 214 family (La 2−x Sr x CuO 4 -LSCO, La 2−x Ba x CuO 4 -LBCO, La 2−x−y Eu y Sr x CuO 4 -LESCO and similar) detects the influence of stripe-related fluctuations [11][12][13][14]16 .…”