Magnetization of ${\mathrm{SrCu}}_2({\mathrm{BO}}_3{)}_2$ in Ultrahigh Magnetic Fields up to 118 T

The magnetization process of the orthogonal-dimer antiferromagnet ${\mathrm{SrCu}}_2({\mathrm{BO}}_3{)}_2$ is investigated in high magnetic fields of up to 118 T. A $1/2$ plateau is clearly observed in the field range 84 to 108 T in addition to $1/8$, $1/4$, and $1/3$ plateaus at lower fields. Using a combination of state-of-the-art numerical simulations, the main features of the high-field magnetization, a $1/2$ plateau of width 24 T, a $1/3$ plateau of width 34 T, and no $2/5$ plateau, are shown to agree quantitatively with the Shastry-Sutherland model if the ratio of inter- to intradimer exchange interactions $J^{\prime }/J=0.63$. It is further predicted that the intermediate phase between the $1/3$ and $1/2$ plateaus is not uniform but consists of a $1/3$ supersolid followed by a $2/5$ supersolid and possibly a domain-wall phase, with a reentrance into the $1/3$ supersolid above the $1/2$ plateau.

Figure 1

Pickup coil signal proportional to the time derivative of the magnetization ($dM/dt$) plotted as a function of time. The magnetic field waveform $H(t)$ is also shown.

Figure 2

The magnetization curve at 2.1 K up to 109 T (shot $A$). Applied fields $H$ are parallel to the $c$ axis of the crystal. The magnetic field derivative of the magnetization ($dM/dH$) curve is displayed as a function of magnetic field $H$. The dotted curve is the magnetization curve reported previously [13]. The $dM/dH$ curve of another measurement up to 118 T (shot $B$) is plotted in the inset.

Figure 3

Phase diagram of the Shastry-Sutherland model in a magnetic field obtained with iPEPS.

Figure 4

Comparison between the experimental magnetization curve and the iPEPS simulation results for $J^{\prime }/J=0.63$. The extent of the $1/3$ and $1/2$ plateaus predicted by the other methods is shown on top of the plateaus.