MC phase diagram for Eq. (1) without disorder at low temperatures. Instead of presenting a three dimensional phase diagram we have chosen to present a two dimensional cut along for simplicity. Five regions are observed: AF, -SC, stripes, coexisting , coexisting , and metallic (a). MC phase diagram including temperature along “Path 1” (b). MC phase diagram along “Path 2” (c). Lattice sizes in all cases are and . (From Ref. 11).
Schematic representation of Sr doping. A chemical dopant (Sr) will not only disorder one site in the -plane, but also neighboring ones, motivating the introduction of “plaquette”-like disorder configurations that affect nearby sites (right/bottom square).
MC phase diagram for model Eq. (1) including quenched disorder (lattices studies are (results shown) and ). Shown are and vs. number of impurities (equal to number of holes). The SC and AF regions with short-range order (dashed lines), and as obtained from the PG (dot-dashed line) are also indicated (a). DOS at points , , and of (a), with a PG (b); (from Ref. 11).
MC phase diagram of model Eq. (5) at . The clean case (, solid lines) is bicritical-like, but with disorder a clustered region between SC and AF opens as well (from Ref. 11).
MC snapshots are shown at (a) and (b), both at and , using the same quenched-disorder configuration. Colors (or shades of gray) indicate the SC phase, while intensities are proportional to . The AF order parameter is not shown. The multiple-color nature of the left snapshot reflects a SC phase randomly distributed (i.e., an overall non-SC state). However, a small external field rapidly aligns those phases, leading to a coherent state as shown on the right.
vs. (see text) on a lattice, with and , at the five points — indicated on the right panel. A “colossal” effect is observed in and , where the state is “clustered.” A much milder (linear) effect occurs far from the SC phase ( and ) (a). The points in the phase diagram where was plotted (b). (From Ref. 11).
MC phase diagram [for Eq. (5)] at . Parameters are , , , with one layer (solid colors) and two layers (dashed line). The addition of an extra layer increases the critical temperature of the superconductor as well as the Néel temperature (a). vs. for , , and clusters. Shown are results with and without disorder (b).
, evaluated via MC, on an lattice for (a) (SC state); , coexisting AF/SC state (b); (AF) (c), and (d) , striped state (from Ref. 15).
Experimental ARPES spectra for LSCO with and . Note the development of a (flat) second high-intensity branch near and the emergence of a strongly dispersive signal at the Fermi level as the system is doped away from the half-filled insulator (reproduced from Ref. 36).
Distribution of for a single configuration of classical fields, corresponding to a SC region of size (a), (b), (c), or (d) on a lattice (i.e., 30%, 15%, 10%, or 5% SC, respectively). Shown is vs. along (from Ref. 15).
Schematic representation of the phase diagrams that our models show in the dirty limit. Of particular interest is the glassy region, proposed to be a mixture of SC and AF clusters, and the , where local order starts upon cooling. This phase diagram has formal similarities with those proposed before for manganites with antiferromagnetism vs. ferromagnetism competition,12,13 and certainly it is in excellent agreement with the experimental phase diagram of LSCO (a). Schematic representation of the “glassy” state that separates the SC and AF regions. The SC clusters (dark regions) usually have different phases (b).
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