Capacitance measurements of chargons in the spin-liquid candidate YCu₃(OH)₆Br₂[Br_1−y(OH)_y] using pulsed magnetic fields of up to 73 T and temperatures down to 0.5 K

The observation of de Haas-van Alphen-type oscillations in YCOB (YCu₃(OH)₆Br₂[Br_1−y(OH)_y]), a kagome-lattice Mott insulator with a 3-eV charge gap, has attracted a great deal of attention. The oscillations provide strong evidence for fermionic spinons in a spin liquid that exists near the 1/9 magnetization plateau. An important contribution to this effect is an effective gauge field; even though the spinon is charge neutral, its motion is accompanied by a backflow of orbital chargon current, which couples to the external magnetic field. In order to study the chargons in more detail, we have performed capacitance measurements on YCOB single crystals in pulsed magnetic fields of up to 73 T and at temperatures down to 500 mK. The field range enables capacitance features close to the 1/9 magnetization plateau to be compared directly with those around the 1/3 plateau, which has a different origin. The talk will describe the methods used for sensitive capacitance measurements in the extreme environment of pulsed magnetic fields and show how the features in the capacitance data reflect the underlying spinon statistics.