Physics Seminar:Chiral Spin-Glass Phases, Fibrous Microreentrances
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  • Physics Seminar:Chiral Spin-Glass Phases, Fibrous Microreentrances

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Title:Chiral Spin-Glass Phases, Fibrous Microreentrances, Nano-Controlled Frustration, and Multiple Chaos

Time: 13:40-

Date: November,16

Place: FENS G032

Speaker: A.Nihat Berker

 A spin-glass phase is obtained, for the first time, from competing chirality interactions and comes with novel phase transition phenomena.[1] The global phase diagram of this frozen-disordered chiral 3-state Potts system in d=3 spatial dimensions is calculated by renormalization-group theory, in temperature, chirality concentration p, and chirality-breaking concentration c, with distinct determination of phase chaos and phase-boundary chaos. The system has ferromagnetic, left-chiral, right-chiral, chiral spin-glass, and disordered phases. The phase boundaries to the ferromagnetic, left- and right-chiral phases show, differently, an unusual, fibrous patchwork (microreentrances) of all four (ferromagnetic, left-chiral, right-chiral, chiral spin-glass) ordered phases, especially in the multicritical region. The chaotic behavior of the interactions under scale change are determined in the chiral spin-glass phase and on the boundary between the chiral spin-glass and disordered phases, showing Lyapunov exponents in magnitudes unexpectedly reversed from ferromagnetic-antiferromagnetic spin-glass systems. The latter, in which ferromagnetic and antiferromagnetic interactions do not match and local odd-clock degrees of freedom inject entropy, are also studied by renormalization-group theory in various integer and fractional spatial dimensions.[2]  We show that with nano-rearrangements of ferromagnetic and antiferromagnetic interactions, the interaction non-matching (aka frustration) can be tuned without changing the material components. Thus, the spin-glass phase never before seen in d=2 dimensions has been obtained and, in the opposite direction, the spin-glass phase always seen in three dimensions has been removed. In the spin-glass phase in even-q-state clock spin models, we show the equivalence of the chaotic distribution of interactions at a given position appearing under consecutive scale changes and the chaotic distribution of interactions in all positions of the system at a given scale.  A universality has been found across the different q values.  In odd-q-state clock spin models, differently, asymmetric phase diagrams, as in quantum spin-glass systems, and many phases in which every point is a critical point have been found.  23 sequenced hierarchical models have been solved and the lower-critical dimension where the spin-glass phase disappears has been precisely determined with the non-simple non-integer value of 2.5210 [3], which also appears to be obeyed by chiral spin-glass ordering.  In very recent work [4], ferromagnetic/antiferromagnetic right/left chiral clock spin-glass systems have been studied, showing rather rich phase diagram sequences, one example of which is shown below.  In this connection, an obtained phase diagram morphing video movie will be shown.

[1] T. Çağlar and A.N. Berker, Phys. Rev. E 94, 032121 (2016).

[2] E. Ilker and A.N. Berker, Phys. Rev. E 87, 032124 (2013); 89, 042139 (2014); 90, 062112 (2014).

[3] M. Demirtaş, A. Tuncer, and A.N. Berker, Phys. Rev. E 92, 022136 (2015).

[4] T. Çağlar and A.N. Berker, manuscript in preparation (2016).