Probing the connections between superconductivity, stripe order, and structure in La1.905Ba0.095Cu

Abstract

The superconducting system La2−xBaxCuO4 is known to show a minimum in the transition temperature, Tc, at x = 1 8 where maximal stripe order is pinned by the anisotropy within the CuO2 planes that occurs in the low-temperature-tetragonal (LTT) crystal structure. For x = 0.095, where Tc reaches its maximum value of 32 K, there is a roughly coincident structural transition to a phase that is very close to LTT. Here we present a neutron scattering study of the structural transition, and demonstrate how features of it correlate with anomalies in the magnetic susceptibility, electrical resistivity, thermal conductivity, and thermoelectric power. We also present measurements on a crystal with 1% Zn substituted for Cu, which reduces Tc to 17 K, enhances the spin stripe order, but has much less effect on the structural transition. We make the case that the structural transition correlates with a reduction of the Josephson coupling between the CuO2 layers, which interrupts the growth of the superconducting order. We also discuss evidence for two-dimensional superconducting fluctuations in the normal state, analyze the effective magnetic moment per Zn impurity, and consider the significance of the anomalous thermopower often reported in the stripeordered phase.

Uniaxial linear resistivity of superconducting La1.905Ba0.095CuO4Wen1, Qi2, Li3 et al. 2012Phys. Rev. BSelf Cite438551View full textAdd to dashboardCite

“…(In fact, it is a surprisingly good description given that we believe that the Josephson coupling is changing in an anomalous fashion in this temperature range due to the underlying structural transition. 30 ) In the fit, T c varies from 31.6 K at 1 T to 30.9 K at 9 T. From the fitted value of A = 1.3 × 10 3 T, we obtain the estimate J ⊥c0 ∼ 1.3 × 10 6 A/cm 2 , which is of the same magnitude as that found by Tinkham 46 in fitting similar data for YBa 2 Cu 3 O 6+x with T c = 91 K.…”

“…We have characterized this behavior with neutron diffraction, thermal conductivity, and thermopower in the following paper, 30 which we will refer to as paper II. A consequence of the transition is a reduction of the interlayer Josephson coupling in the LTLO phase, 31 resulting in the sharp structure in ρ ⊥ near 27 K when modest H ⊥ is applied, 30 as apparent in Fig. 1(a) and (b).…”

Reconciliation of local and long-range tilt correlations in underdopedLa2−xBaxCuO4(0≤xBožin1, Zhong2, Knox3 et al. 2015Phys. Rev. BSelf Cite297190View full textAdd to dashboardCite

“…Both powder [8,15] and single-crystal [16][17][18] diffraction studies clearly demonstrate that the transition to the low-temperature structure, involving a change in tilt direction of the CuO 6 octahedra, is of first order. A surprisingly different perspective is given by a pair-distribution-function (PDF) analysis of neutron scattering measurements [19].…”

Transport properties of stripe-ordered high Tc cuprates

“…While stripe order should certainly modify the nominal Fermi surface, the empirical fact that the antinodal states are gapped means that the impact of stripe order is not readily detected by ARPES. The onset of a coherent antinodal gap below T co associated with PDW superconductivity [20,52] provides another possible mechanism for changes in the thermopower and Hall effect [51]. The onset of a field-symmetric Nernst signal in LBCO x = 1/8 [93] provides a new mystery, although a polar Kerr effect study provides supporting evidence for time-reversal symmetry breaking [102].…”

“…In the case of LBCO x = 1/8, however, where the negative thermopower occurs at zero field, angle-resolved photoemission measurements [49] indicate the presence of a substantial gap for the antinodal states, so that it seems unlikely that such states contribute directly to the negative thermopower [50]. Alternatively, Wen et al [51] have argued that the asymmetry of the antinodal states about the Fermi level in the normal state may be responsible for the large positive value of S ab ; the development of a PDW gap symmetric about E F in the antinodal region [52] might eliminate that large positive contribution, leaving behind a residual negative S ab due to ungapped nodal-arc states.…”