Incomplete Devil’s Staircase in the Magnetization Curve ofSrCu2(BO3)2

Abstract

We report on NMR and torque measurements on the frustrated quasi-two-dimensional spin-dimer system SrCu(2)(BO(3))(2) in magnetic fields up to 34 T that reveal a sequence of magnetization plateaus at 1/8, 2/15, 1/6, and 1/4 of the saturation and two incommensurate phases below and above the 1/6 plateau. The magnetic structures determined by NMR involve a stripe order of triplets in all plateaus, suggesting that the incommensurate phases originate from proliferation of domain walls. We propose that the magnetization process of SrCu(2)(BO(3))(2) is best described as an incomplete devil's staircase.

Crystals of Bound States in the Magnetization Plateaus of the Shastry-Sutherland Model

“…It is also shown that the crystals formed by the bound states naturally explain the sequence of magnetization plateaus observed in SrCu 2 (BO 3 ) 2 . In particular, the 2/15 plateau is made of a simple and regular pattern of bound states, in contrast to the more complicated patterns of triplets which were previously suggested [12,21,24].Method -Our results have been obtained with infinite projected entangled-pair states (iPEPS) -a variational tensornetwork ansatz to represent a two-dimensional wave function in the thermodynamic limit [31][32][33]. It consists of a cell of tensors which is periodically repeated on the lattice, where in the present work we use one tensor per dimer.…”

“…It is also shown that the crystals formed by the bound states naturally explain the sequence of magnetization plateaus observed in SrCu 2 (BO 3 ) 2 . In particular, the 2/15 plateau is made of a simple and regular pattern of bound states, in contrast to the more complicated patterns of triplets which were previously suggested [12,21,24].…”

“…4(d)) has clearly a lower energy than the previously proposed candidates of triplet crystals [12,21,24].…”

“…A famous example is the Shastry-Sutherland model (SSM) [2], which is believed to accurately capture the physics of the orthogonal-dimer antiferromagnet SrCu 2 (BO 3 ) 2 . A big effort has been invested in understanding the appearance of various magnetization plateaus observed in experiments [3][4][5][6][7][8][9][10][11][12][13]. Early on it was found that the SSM has almost localized triplet excitations [5,14] which suggests that each plateau corresponds to a particular crystal of localized triplets.…”

“…Two triplet crystals have been proposed: the diamond pattern shown in Fig. 2(a) with basis vectors v 1 = (2, −2) and v 2 = (2, 2) [12,20,24], and a rhomboid pattern defined by v 1 = (2, −2) and v 2 = (3, 1) [6,7,10,20] (see also Supplemental Material [44]). In Fig.…”