Nematic quantum phases in the bilayer honeycomb antiferromagnet

Abstract

The spin−1/2 Heisenberg antiferromagnet on the honeycomb bilayer lattice is shown to display a rich variety of semiclassical and genuinely quantum phases, controlled by the interplay between intralayer frustration and interlayer exchange. Employing a complementary set of techniques, comprising spin rotationally invariant Schwinger boson mean field theory, bond operators, and series expansions we unveil the quantum phase diagram, analyzing low-energy excitations and order parameters. By virtue of Schwinger bosons we scan the complete range of exchange parameters, covering both long range ordered as well as quantum disordered ground states and reveal the existence of an extended, frustration induced lattice nematic phase in a range of intermediate exchange unexplored so far. * Electronic address: zhanghao@iphy.ac.cn † Electronic address: lamas@fisica.unlp.edu.ar ‡ Electronic address: w.brenig@tu-bs.de

Series expansion studies of the $J_1$-$J_2$-Heisenberg bilayer

“…Combining this with the critical line from the resummed SE, it is very tempting to speculate that the single-layer QSL, anticipated on the line 1 J1 = 0, is confined to the lower part of this hourglass and terminates within its constriction. This is very reminiscent of a somewhat similar situation of a QSL surrounded by a QDM and two reentrant LRO phases in the frustrated honeycomb bilayer Heisenberg model [50].…”

“…4 (b). Even more surprising, such a phase, separating QDM from magnetic spiral states has been found also in the frustrated honeycomb bilayer Heisenberg model [50], where the intervening phase displayed nematic character. Consolidating our present findings by resummation or higher-order SE remains an open question beyond this work.…”

“…While in some cases the reduction of the dimer exchange may lead to condensation of triplons into sought-for quantum phases of some non-dimerized original model, bilayer systems host their own unique set of physics. For this reason, a variety of bilayer systems have previously been studied under various objectives, e.g., uncovering rich phase diagrams [49][50][51][52][53], examining the crossing to 3D bulk materials [54], investigating effects of disorder [55] and hole doping [56] or analyzing emergent bound states [57] and topological excitations [58]. On the material side, an extensive number of systems exist, which are related to this theme, including Li 2 VOSiO 4 [45], BaCuSi 2 O 6 [59,60], TlCuCl 3 [61], Ba 3 Mn 2 O 8 [62], and SrCu 2 (BO 3 ) 2 [63].…”

Exploring neural network training strategies to determine phase transitions in frustrated magnetic models

“…The transfer learning results presented in this work indicate that neural networks, in particular convolutional networks, can be adequate generic classifiers, exhibiting high performance when properly trained in minimal architectures, even in cases of high degeneracy such as the frustrated systems already analyzed. We plan to apply similar methods to other frustrated models at classical [44] and quantum level [45][46][47].…”