Reinvestigation of crystal symmetry and fluctuations in La${}_2$CuO${}_4$

Abstract

New surprises continue to be revealed about La${}_2$CuO${}_4$, the parent compound of the original cuprate superconductor. Here we present neutron scattering evidence that the structural symmetry is lower than commonly assumed. The static distortion results in anisotropic Cu-O bonds within the CuO${}_2$ planes; such anisotropy is relevant to pinning charge stripes in hole-doped samples. Associated with the extra structural modulation is a soft phonon mode. If this phonon were to soften completely, the resulting change in CuO${}_6$ octahedral tilts would lead to weak ferromagnetism. Hence, we suggest that this mode may be the "chiral" phonon inferred from recent studies of the thermal Hall effect. We also note the absence of interaction between the antiferromagnetic spin waves and low-energy optical phonons, in contrast to what is observed in hole-doped samples.

12 pages, 10 figures; accepted version

References in corpus (13)

• Mantid - Data Analysis and Visualization Package for Neutron Scattering and $\mu SR$ Experiments
• Charge density wave fluctuations in La2-xSrxCuO4 and their competition with superconductivity
• Giant thermal Hall conductivity from neutral excitations in the pseudogap phase of cuprates
• Phonons become chiral in the pseudogap phase of cuprates
• Rotated stripe order and its competition with superconductivity in La${}_{1.88}$Sr${}_{0.12}$CuO${}_4$
• Cuprate superconductors as viewed through a striped lens
• Crystal structure and high-field magnetism of La2CuO4
• Thermal Hall conductivity in the cuprate Mott insulators Nd${}_2$CuO${}_4$ and Sr${}_2$CuO${}_2$Cl${}_2$
• 2D orbital-like magnetic order in $\mathrm{L}{\mathrm{a}}_{2-\mathrm{x}}\mathrm{S}{\mathrm{r}}_{\mathrm{x}}\mathrm{Cu}{\mathrm{O}}_4$
• Anomalous mirror symmetry breaking in a model insulating cuprate Sr${}_2$CuO${}_2$Cl${}_2$
• Consideration of Thermal Hall Effect in Undoped Cuprates
• Electron-phonon coupling and superconductivity in the doped topological-crystalline insulator (Pb${}_{0.5}$Sn${}_{0.5}$)${}_{1-x}$In${}_x$Te
• Gapless spin excitations in superconducting La${}_{2-x}$Ca${}_{1+x}$Cu${}_2$O${}_6$ with $T_c$ up to 55 K

Cited by in corpus (8)

• Strongly-overdoped La${}_{2-x}$Sr${}_x$CuO${}_4$: Evidence for Josephson-coupled grains of strongly-correlated superconductor
• Effect of the electronic charge gap on LO bond-stretching phonons in undoped La${}_2$CuO${}_4$ calculated using LDA+U
• Thermal Hall Effect in the Kitaev-Heisenberg System with Spin-Phonon Coupling
• Crystal Symmetry of Stripe Ordered La1.88Sr0.12CuO4
• Structural origins of the infamous "Low Temperature Orthorhombic" to "Low Temperature Tetragonal" phase transition in high-Tc cuprates
• The hidden competing phase revealed by first-principles calculations of phonon instability in the nearly optimally doped cuprate La${}_{1.875}$Sr${}_{0.125}$CuO${}_4$
• Spin canting and lattice symmetry in La${}_2$CuO${}_4$
• Charge density waves and pinning by lattice anisotropy in 214 cuprates