Research: Probing stripe order in a cuprate superconductor with uniaxial stress

High-temperature superconductivity in cuprates appears when mobile charge carriers are doped into the copper-oxygen plane. In undoped compounds, there is one charge carrier per Cu site, and these localise to form a robust antiferromagnetic state; adding charge carriers destroys this state and leads to superconductivity. In La_2-xBa_xCuO₄, when the charge carrier doping reaches 1/8 per Cu site, another state with suppressed superconductivity appears: a stripe state, in which there are static lines of antiferromagnetic order and charge within each CuO₂ sheet. This stripe ordered state is finely balanced: high temperature superconductivity is restored with only a small shift in doping away from 1/8. In this work we show how delicate and finely-tuned the stripe state is: with a uniaxial stress of only 60 MPa – a very low pressure for modifying the electronic properties of inorganic compounds – the stripe state is suppressed and high-temperature superconductivity restored. That the stripe order is suppressed is a key result of this paper: an alternative possibility is that the stripes would be re-oriented in a slight way.  Muon spin rotation is a technique that identifies the strength and the volume fraction of magnetic order. In the figure, the oscillation of the spin polarization of muons implanted into the sample is a rigorous indicator of magnetic order, and it can be seen that the amplitude of this oscillation is suppressed as stress is applied.

Z. Guguchia, D. Das, C. N. Wang, T. Adachi, N. Kitajima, M. Elender, F. Brückner, S. Ghosh, V. Grinenko, T. Shiroka, M. Müller, C. Mudry, C. Baines, M. Bartkowiak, Y. Koike, A. Amato, J. M. Tranquada, H.-H. Klauss, C. W. Hicks, H. Luetkens,
Using Uniaxial Stress to Probe the Relationship between Competing Superconducting States in a Cuprate with Spin-stripe Order,
Phys. Rev. Lett. 125, 097005 (2020) (arXiv)