Uniaxial strain tuning of competing superconductiv­ity and nanoscale magnetic order in La2-xBaxCuO4

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.

Publication: Z. Guguchia et al., Phys. Rev. Lett. 125, 097005 (August 2020)