Stripe order, depinning, and fluctuations inLa1.875Ba0.125CuO4and

Abstract

We present a neutron scattering study of stripe correlations measured on a single crystal of La1.875Ba0.125CuO4. Within the low-temperature-tetragonal (LTT) phase, superlattice peaks indicative of spin and charge stripe order are observed below 50 K. For excitation energieshω ≤ 12 meV, we have characterized the magnetic excitations that emerge from the incommensurate magnetic superlattice peaks. In the ordered state, these excitations are similar to spin waves. Following these excitations as a function of temperature, we find that there is relatively little change in the Q-integrated dynamical spin susceptibility forhω ∼ 10 meV as stripe order disappears and then as the structure transforms from LTT to the low-temperature-orthorhombic (LTO) phase. The Qintegrated signal at lower energies changes more dramatically through these transitions, as it must in a transformation from an ordered to a disordered state. We argue that the continuous evolution through the transitions provides direct evidence that the incommensurate spin excitations in the disordered state are an indicator of dynamical charge stripes. An interesting feature of the thermal evolution is a variation in the incommensurability of the magnetic scattering. Similar behavior is observed in measurements on a single crystal of La1.875Ba0.075Sr0.050CuO4; maps of the scattered intensity in a region centered on the antiferromagnetic wave vector and measured athω = 4 meV are well reproduced by a model of disordered stripes with a temperature-dependent mixture of stripe spacings. We discuss the relevance of our results to understanding the magnetic excitations in cuprate superconductors.

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].…”

Cuprate superconductors in the vicinity of a Pomeranchuk instability

“…3(b) tends to favor a larger η. Such a change was recently observed in LBCO with x = 0.125, [8] although the authors [8] interpreted the data differently as due to a charge stripe formation.…”

“…In particular, dFSD correlations are essential for the pronounced anisotropy observed in untwinned YBCO [6,7] and the sizable change of incommensurability at the onset temperature of the LTT phase transition in LBCO. [8] Cuprate superconductors are expected to be in the vicinity of the dFSD instability, the so-called d-wave Pomeranchuk instability, leading to a giant response to a small external xy anisotropy. …”

“…While the IC signals retain fourfold symmetry, namely η x = η y = η, the value of η turns out to show a sizable change when the lattice undergoes the structural phase transition from the low-temperature orthorhombic structure (LTO) to the low-temperature tetragonal structure (LTT) in La 2−x Ba x CuO 4 (LBCO) with x = 0.125. [8] In this paper, we show that the above experimental data are naturally understood in terms of dFSD correlations. While sizable dFSD correlations were found in the slave-boson, [1] exact diagonalization, [9] and variational Monte Carlo [5] techniques in the t-J model, and in various renormalization group analyses [2,[10][11][12] in the Hubbard model, we employ the t-J A c c e p t e d m a n u s c r i p t model in the slave-boson mean-field theory, which has the advantage of dealing with both d-wave singlet pairing and dFSD correlations on an equal footing as well as performing a systematic calculation of magnetic excitations.…”

Neutron Scattering Studies of Antiferromagnetic Correlations in Cuprates

“…Also included in the figure are results for La 2−x Ba x CuO 4 with x = 1 8 [41,42], a compound of interest because of the occurrence of charge and spin stripe order [43] (to be discussed later) and a strongly suppressed T c . At the lowest energies, the spin excitations rise out of incommensurate magnetic (two-dimensional) Bragg peaks.…”