engleski

Charge stripe melting in cuprates: an experimental study

We present the experimental detection of a previously unseen electronic phase in the cuprate Eu-LSCO (La2-x-yEuySrxCuO4 , with y = 0.2), an intermediate between the well-known charge stripe ordered phase and the Fermi liquid. While its origin remains unknown, our experimental investigation employing several techniques reveals surprising properties of the new phase. We have used nuclear quadrupole resonance (NQR) of copper nuclei in the Cu-O planes of high quality Eu-LSCO single crystals to obtain information on the local electronic dynamics, detecting a decrease of signal intensity (partial 'wipeout' effect) in the new phase. This is indicative of strong spin fluctuations, as already observed in other charge- and spin-ordered cuprates, and the partial signal decrease hints at significant nanoscale inhomogeneity of the electron system. Insight into collective electronic behaviour is obtained from nonlinear conductivity measurements performed in a specially constructed high-sensitivity probe. Nonlinear conductivity shows a divergence at the temperature corresponding to the onset of the intermediate phase, and since all linear transport coefficients are smooth close to the onset temperature, this suggests that the nature of the order in the intermediate phase is highly unusual. While Eu-LSCO was chosen as a model system due to prominent charge stripe order and the absence of interfering structural transitions, the observation of the unconventional intermediate phase could be of much broader importance for the physics of cuprates. Although evidence mounts that 'stripe-like' electronic phases are an essential ingredient of cuprate physics, unambiguously detecting them has been notoriously difficult if long-range translational order is absent. Our combination of experimental techniques enabled us to study just such a phase in unprecedented detail, uncovering its extraordinary properties.

cuprates ; charge order ; nematic phase

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