APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016;
Baltimore, Maryland
Session A3: Recent Progress on 'Order by Disorder' Phenomena
8:00 AM–11:00 AM,
Monday, March 14, 2016
Room: Ballroom III
Sponsoring
Units:
DCMP GMAG
Chair: Israel Klich, University of Virginia
Abstract ID: BAPS.2016.MAR.A3.3
Abstract: A3.00003 : The many faces of order-by-disorder in rare-earth pyrochlore magnets
9:12 AM–9:48 AM
Preview Abstract
Abstract
Author:
Michel J P Gingras
(University of Waterloo)
Order-by-disorder (ObD) is a concept of central importance in the field of frustrated magnetism.
Saddled with large accidental degeneracies, a subset of states,
those that support the largest quantum and/or thermal fluctuations,
may be selected to form true long-range order.
More formally, one often begins describing a system
in terms of some order parameter $m$ with the low-energy
description framed in terms of an effective action
$\Gamma(m)$. In each ObD scenario, one starts from
an artificial limit where there is an accidental degeneracy;
that is the effective action at this point, $\Gamma_0(m)$, has an accidental
symmetry. One may then view ObD phenomena as cases where
the corrections to $\Gamma_0(m)$ arise through some form of
fluctuation corrections, may they be thermal, quantum or virtual, towards an enlarged higher energy Hilbert space.
In the rare-earth pyrochlore oxides, of formula $R_2$$M_2$O$_7$,
the trivalent magnetic rare-earth ions $R^{3+}$
(e.g $R=$Gd, Er, Yb; $M=$Ti, Sn is
non-magnetic) reside on a three-dimensional pyrochlore lattice of corner-sharing tetrahedra.
This architecture is prone to a high degree of magnetic frustration, with the
$R_2M_2$O$_7$ pyrochlore materials having been found over the past twenty years to display
a gamut of exotic phenomena. In this talk, I will discuss three such phenomena:
(i) the intermediate partially-ordered
multiple-$k$ state between $0.7$K and $1$K in the Gd$_2$Ti$_2$O$_7$ Heisenberg
antiferromagnet~\footnote{$\,$PRL \textbf{114}, 130601 (2015)}, (ii) the ordered $\psi_2$ state selection in the $XY$ Er$_2$Ti$_2$O$_7$ antiferromagnet~\footnote{$\,$arXiv:1510.04292} and (iii) the
puzzling high sample sensitivity of the Yb$_2$Ti$_2$O$_7$ ``quantum spin ice'' candidate~\footnote{$\,$arXiv:1505.05499}.
I will argue that in all three cases, some form of fluctuation corrections to their simplest
$\Gamma_0(m)$ description play a significant role in the state selection and experimentally observed behaviors.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2016.MAR.A3.3