Charge Condensation and Lattice Coupling Drives Stripe Formation in Nickelates

Y. Shen, G. Fabbris, H. Miao, Y. Cao, D. Meyers, D. G. Mazzone, T. A. Assefa, X. M. Chen, K. Kisslinger, D. Prabhakaran, A. T. Boothroyd, J. M. Tranquada, W. Hu, A. M. Barbour, S. B. Wilkins, C. Mazzoli, I. K. Robinson, and M. P. M. Dean

Phys. Rev. Lett. 126, 177601 – Published 30 April 2021

Abstract

Revealing the predominant driving force behind symmetry breaking in correlated materials is sometimes a formidable task due to the intertwined nature of different degrees of freedom. This is the case for ${La}_{2 - x} {Sr}_{x} {NiO}_{4 + δ}$ , in which coupled incommensurate charge and spin stripes form at low temperatures. Here, we use resonant x-ray photon correlation spectroscopy to study the temporal stability and domain memory of the charge and spin stripes in ${La}_{2 - x} {Sr}_{x} {NiO}_{4 + δ}$ . Although spin stripes are more spatially correlated, charge stripes maintain a better temporal stability against temperature change. More intriguingly, charge order shows robust domain memory with thermal cycling up to 250 K, far above the ordering temperature. These results demonstrate the pinning of charge stripes to the lattice and that charge condensation is the predominant factor in the formation of stripe orders in nickelates.

Received 27 October 2020
Accepted 31 March 2021
Corrected 10 May 2021

DOI:https://doi.org/10.1103/PhysRevLett.126.177601

Physics Subject Headings (PhySH)

Charge order Magnetic order

Complex oxides

Coherent X-ray scattering

Condensed Matter, Materials & Applied Physics

Corrections

10 May 2021

Correction: The middle initial of the seventh author was missing and has been fixed.

Authors & Affiliations

Y. Shen^1,*, G. Fabbris ^1,2, H. Miao ^1,3, Y. Cao^1,4, D. Meyers^1,5, D. G. Mazzone ^1,6, T. A. Assefa ¹, X. M. Chen¹, K. Kisslinger⁷, D. Prabhakaran⁸, A. T. Boothroyd⁸, J. M. Tranquada ¹, W. Hu⁹, A. M. Barbour⁹, S. B. Wilkins⁹, C. Mazzoli⁹, I. K. Robinson¹, and M. P. M. Dean ^1,†

¹Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
²Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA
³Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
⁴Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
⁵Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, USA
⁶Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
⁷Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA
⁸Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, United Kingdom
⁹National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA

^*yshen@bnl.gov
^†mdean@bnl.gov

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Vol. 126, Iss. 17 — 30 April 2021

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Images

Figure 1
Experimental configuration and CO and SO superlattice peaks. (a) The instrumental setup for the measurements at CSX. The x-ray beam is set to the Ni $L_{3}$ -edge energy and tuned in order to maximize the strength of the CO and SO intensity [39]. It then propagates through the pinhole and is scattered by the LSNO sample onto the detector. For the domain memory study, a $0.5 − μ m$ -thick Pt mask was deposited on the sample [39]. (b) An optical micrograph of the Pt mask on the (110) surface of a LSNO single crystal. (c) Temperature dependence of the correlation lengths along $[H, H, 0]$ and $[0, 0, L]$ directions. The correlation length is defined as $ξ = d / HWHM$ , where $HWHM$ stands for half width at half maximum in reciprocal lattice units and $d$ is the unit cell size in the appropriate direction [44]. (d) Temperature dependence of the peak heights evaluated from fitting of the CO and SO superlattice peaks, which are normalized according to their values at 60 K. The signals were fitted with a three-dimensional Lorentzian function. (e) Incommensurability defined by the peak position of the CO $Q$ vector as a function of the temperature. The shaded areas indicate the onset temperature range for CO and SO.
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Figure 2
Speckle patterns of CO and SO. (a),(b) Representative detector images around the CO and SO superlattice peaks measured with a $10 μ m$ pinhole. The white pixels arise from the beamstop or detector errors and are omitted from the data. (c), (d) Line cuts through the horizontal red dashed lines in (a) and (b). The envelope of the peak is estimated by smoothing and fitting processes that are shown as red and orange lines, respectively. The black dashed lines are uniform fluorescent background evaluated from fittings.
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Figure 3
Temporal stability of CO and SO. (a),(b) Time dependence of the intermediate scattering functions at different temperatures. The solid lines are guides to the eye. (c),(d) The scattering functions after certain time delays.
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Figure 4
Domain memory in CO but not SO. (a),(b) Representative speckle images before and after thermal cyclings, which are indicated by the curved arrows. The open circles stand for the cycling temperatures $T_{cycle}$ . For each measurement, we collected images at 70 K, changed the temperature to $T_{cycle}$ , and waited for 10 min. Then the sample was cooled back to 70 K and equilibrated for 30 min before collecting another image. For both the heating and cooling processes, the temperature ramping rate was fixed to $4 K / \min$ . The white bar in the first speckle image indicates $10^{- 3} Å^{- 1}$ . (c) Temperature dependence of the normalized speckle cross-correlation function $ξ_{CC}$ . The solid and dashed lines are guides to the eye. The shaded area indicates the range of CO and SO transition temperatures.
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