Inverse order-disorder transition of charge stripes

Abstract

We report an unusual transition behavior of charge stripes in La 1.67 Sr 0.33 NiO 4 using x-ray scattering. The segregated holes in La 1.67 Sr 0.33 NiO 4 are observed to form anisotropic stripes in the a × b plane of the crystal space below the transition temperature T 238 K, and at the same time, display an unusual inverse order-disorder transition along the c axis. Using a phenomenological Landau theory, we show that this inverse transition is due to the interlayer coupling between the charge and spin orders. This discovery points to the importance of the interlayer correlations in the strongly correlated electrons system. Doped Mott insulators have served as a rich playground for strongly correlated electron systems, yet the physics is still not fully comprehended. The complexity results from the interplay between competing orders, such as charge, spin, orbital, and lattice, and the strong quantum fluctuations [1]. In the model system of high-T c superconductor La 2 CuO 4 , substitution of La with Sr or Ba induces segregated holes that form unidirectional self-organized electronic stripes in the a × b plane of the crystal space [2]. Experimentally, such a phenomenon has been observed in neutron, x-ray, and electron diffractions, and it is shown that transport behavior depends strongly on the hole concentration [3,4]. These ordered electronic phases are understood to arise due to the Coulomb-frustrated separation of electronic domains at the nanoscale [5,6]. In these phases, there exist locally Mott insulating regions with magnetic (spin) order, separated by more metallic regions with higher concentrations of doped holes. Taking the in-plane fluctuations into consideration, these ordered charges could form the exotic electronic liquid-crystal phases [7,8]. This intralayer coupling between the ordered charges and spins has been widely discussed and observed in Cu-and Fe-based * chd@mail.tku.edu.tw † yjkao@phys.ntu.edu.tw superconductors [9][10][11][12]. It is natural to ask what role the interlayer coupling between the charge and spin orders in different planes plays in these systems [13,14].Using x-ray scattering measurements on single-crystal samples of La 2−x Sr x NiO 4 (LSNO), we report an unusual inverse order-disorder transition due to the interlayer coupling of the in-plane charges and spins. It is well established that there can exist both smectic and striped-liquid phases of in-plane charge and spin ordering in LSNO [15][16][17][18]. LSNO has a tetragonal structure [ Fig. 1(a)], and is isostructural with the superconducting cuprate LSCO. Both LSNO and LSCO are antiferromagnetic (AFM) Mott insulators in the absence of hole doping. While LSCO becomes a high-T c superconductor for small amounts of hole doping, LSNO remains insulating for doping levels of up to 90% [19].In LSNO the doped holes condense, leaving, within each two-dimensional (2D) NiO layer, an alternating pattern of AFM domains (spin stripes) separated by charge stripes [ Fig. 1(b)]. In the reciprocal space of the tetragonal crystal structur...

Finite-temperature Wigner solid and other phases of ripplonic polarons on a helium film

“…This sort of transition, known as "freezing by heating" transition, has been predicted for mesoscopic systems 49,50 and recently demonstrated for colloids driven by a non-uniform force 51 . This counter-intuitive behavior does not violate principles of thermodynamics and has been observed both in non-equilibrium and equilibrium systems, see, e. g., 52,53 .…”

Real Space Imaging of Spin Stripe Domain Fluctuations in a Complex Oxide

“…Usually, the measured SO or CO stripes show limited spatial correlation, implying the presence of stripe domains. Based on a phenomenological Landau and cluster models, the spin and lattice coupling are predicted to play a fundamental role in stabilizing SO stripes [5,[21][22][23]. Recent x-ray photon correlation spectroscopy (XPCS) measurements have observed slow fluctuations of SO stripes in particular LSNO crystals [24,25].…”