Spins, stripes, and superconductivity in hole-doped cuprates

Abstract

Abstract. One of the major themes in correlated electron physics over the last quarter century has been the problem of high-temperature superconductivity in hole-doped copper-oxide compounds. Fundamental to this problem is the competition between antiferromagnetic spin correlations, a symptom of strong Coulomb interactions, and the kinetic energy of the doped carriers, which favors delocalization. After discussing some of the early challenges in the field, I describe the experimental picture provided by a variety of spectroscopic and transport techniques. Then I turn to the technique of neutron scattering, and discuss how it is used to determine spin correlations, especially in model systems of quantum magnetism. Neutron scattering and complementary techniques have determined the extent to which antiferromagnetic spin correlations survive in the cuprate superconductors. One experimental case involves the ordering of spin and charge stripes. I first consider related measurements on model compounds, such as La 2−x Sr x NiO 4+δ , and then discuss the case of La 2−x Ba x CuO 4 . In the latter system, recent transport studies have demonstrated that quasi-two-dimensional superconductivity coexists with the stripe order, but with frustrated phase order between the layers. This has led to new concepts for the coexistence of spin order and superconductivity. While the relevance of stripe correlations to high-temperature superconductivity remains a subject of controversy, there is no question that stripes are an intriguing example of electron matter that results from strong correlations.Keywords: superconductivity, antiferromagnetism, charge order, stripes, cuprates, nickelates, neutron scattering PACS: 78.70.Nx OPENING REMARKSCuprate superconductivity is a fascinating field, with an enormous literature. There have been a great many measurements done on a wide variety of cuprate families. There are numerous theoretical perspectives on the nature of these materials and on the mechanism of superconductivity.I approach this topic not as an unbiased outside observer, but as a participant who has been around from the beginning. My purpose here is not to present a balanced review of all work and perspectives in the field, as there would be too much to cover. Instead, I will present one story about hole-doped cuprates, based largely on experiment and especially on neutron scattering studies. Since one of the main advantages of neutrons is their ability to follow dynamic antiferromagnetic spin correlations, it should come as no surprise that they will play a key role in the story.I have tried to cite sufficient references (especially review articles) so that the curious reader can find further information and potentially a starting point in searching the broader literature. I have not attempted to cite all relevant work, as that would have been

Stacked charge stripes in the quasi-2D trilayer nickelate La 4 Ni 3 O 8

“…We also find similar signatures in transport, magnetic, and thermodynamic data measured on La-438 crystals as those reported in the unambiguously identified charge stripe phase LSNO-1/3 (7,16,27,49). Fig.…”

“…Many mixed valent TMOs adopt insulating "charge ordered" states, in which an inhomogeneous but long-range ordered configuration of the charge density condenses from a uniform metallic state (5). The real space pattern of charge order varies by material (6)(7)(8)(9), but a typically observed motif is some variety of charge stripes. Such stripes have been observed in cobaltites (10)(11)(12), cuprates (13)(14)(15), nickelates (16)(17)(18)(19), and manganites (20)(21)(22), albeit with highly materials-dependent configurations that hinge on a balance among Coulomb, lattice, and magnetic exchange energies.…”

“…Instead of superconductivity, however, the ground state of such quasi-2D, octahedrally coordinated nickelates is marked by static charge and spin stripes, with a threefold superlattice (SL) periodicity for compositions near x = 1/3 [La 5/3 Sr 1/3 NiO 4 (LSNO-1/3)] found to be particularly stable (7). Despite this ubiquitous behavior for octahedrally coordinated nickelates, Anisimov et al (29) have suggested that Ni 1+ in a square planar coordination with O ions can form an S = 1/2 antiferromagnetic (AFM) insulator that may be doped with low-spin (S = 0) Ni 2+ holes to yield a superconductor.…”

Temperature and doping induced instabilities of the repulsive Hubbard model on the Lieb lattice

“…11. This state resembles the diagonal stripe order [72,73], where the direction of the stripes is at an angle to the lattice bonds.…”

Measurements of Stationary Josephson Current between High- Tc Oxides as a Tool to Detect Charge Density Waves

“…But they are so complex that researchers are forced to consider them separately in order to find the key concepts and express key ideas explaining the huge totality of experimental data. General discussion and the analysis of high-T c -oxide superconductivity can be found in comprehensive reviews [21,25,42,50,53,65,73,75,78,80,86,89,104]. In particular, the main questions to be solved are as follows: (i) Is superconductivity in cuprates a conventional one based on the Cooper pairing concept?…”