scholarly journals Direct Visualization of Spatial Inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4

2019 ◽  
Vol 4 (3) ◽  
pp. 77 ◽  
Author(s):  
Gaetano Campi ◽  
Nicola Poccia ◽  
Boby Joseph ◽  
Antonio Bianconi ◽  
Shrawan Mishra ◽  
...  
Keyword(s):  
Phase Separation ◽  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Spatial Inhomogeneity ◽  
Strongly Correlated ◽  
Strongly Correlated Electron ◽  
Scale Free ◽  
Spin Order ◽  
Correlated Electron

In several strongly correlated electron systems, the short range ordering of defects, charge and local lattice distortions are found to show complex inhomogeneous spatial distributions. There is growing evidence that such inhomogeneity plays a fundamental role in unique functionality of quantum complex materials. La1.72Sr0.28NiO4 is a prototypical strongly correlated perovskite showing spin stripes order. In this work we present the spatial distribution of the spin order inhomogeneity by applying micro X-ray diffraction to La1.72Sr0.28NiO4, mapping the spin-density-wave order below the 120 K onset temperature. We find that the spin-density-wave order shows the formation of nanoscale puddles with large spatial fluctuations. The nano-puddle density changes on the microscopic scale forming a multiscale phase separation extending from nanoscale to micron scale with scale-free distribution. Indeed spin-density-wave striped puddles are disconnected by spatial regions with negligible spin-density-wave order. The present work highlights the complex spatial nanoscale phase separation of spin stripes in nickelate perovskites and opens new perspectives of local spin order control by strain.

Phase Separation in a Spin Density Wave State of Twisted Bilayer Graphene

JETP Letters ◽  
2020 ◽  
Vol 112 (10) ◽  
pp. 651-656
Author(s):  
A. O. Sboychakov ◽  
A. V. Rozhkov ◽  
K. I. Kugel ◽  
A. L. Rakhmanov
Keyword(s):  
Phase Separation ◽  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Bilayer Graphene ◽  
Wave State ◽  
Twisted Bilayer Graphene

scholarly journals The Ancient Romans’ Route to Charge Density Waves in Cuprates

2019 ◽  
Vol 4 (2) ◽  
pp. 60 ◽  
Author(s):  
Sergio Caprara
Keyword(s):  
Charge Density ◽  
Density Wave ◽  
Metallic Phase ◽  
Charge Density Waves ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Density Waves ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron

An account is given of the main steps that led the research group in Rome, to which the author belongs, to the formulation of the charge-density-wave scenario for high- T c superconducting cuprates. The early finding of the generic tendency of strongly correlated electron systems with short range interactions to undergo electron phase separation was subsequently contrasted with the homogenizing effect of the long-range Coulomb interaction. The two effects can find a compromise in the formation of incommensurate charge density waves. These charge density waves are inherently dynamical and are overdamped as a consequence of the possibility to decay in electron-hole pairs, yet tend to maintain a (quantum) critical character, which is mirrored in their marked momentum and frequency dependence and in their strong variation with temperature and doping. These dynamical incommensurate charge density waves act as mediators of pairing lading to high- T c superconductivity, and provide the scattering mechanism that produces the observed violation of the Fermi-liquid paradigm in the metallic phase.

scholarly journals Nanoscale Phase Separation of Incommensurate and Quasi-Commensurate Spin Stripes in Low Temperature Spin Glass of La2−xSrxNiO4

2021 ◽  
Vol 6 (4) ◽  
pp. 45
Author(s):  
Gaetano Campi ◽  
Antonio Bianconi ◽  
Alessandro Ricci
Keyword(s):  
Phase Separation ◽  
Low Temperature ◽  
Spatial Organization ◽  
Density Wave ◽  
Spin Density Wave ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Strongly Correlated ◽  
Nanoscale Phase Separation ◽  
Striped Phases

While spin striped phases in La2−xSrxNiO4+y for 0.25 < x < 0.33 are the archetypal case of a 1D spin density wave (SDW) phase in doped antiferromagnetic strongly correlated perovskites, few information is available on the SDW spatial organization. In this context, we have measured the spatial variation of the wave vector of the SDW reflection profile by scanning micro X-ray diffractions with a coherent beam. We obtained evidence of a SDW order–disorder transition by lowering a high temperature phase (T > 50 K) to a low temperature phase (T < 50 K). We have identified quasi-commensurate spin stripe puddles in the ordered phase at 50 < T < 70 K, while the low temperature spin glassy phase presents a nanoscale phase separation of T = 30 K, with the coexistence of quasi-commensurate and incommensurate spin stripe puddles assigned to the interplay of quantum frustration and strong electronic correlations.

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