Dielectric and transient electrical response of SmB6 single crystals

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We report results from an in–plane and out–of–plane impedance study on SmB6 single crystals, performed at low temperatures and over a wide frequency range. A universal equivalent circuit describes the dielectric behavior of this system across the transition, from surface to bulk dominated electrical conduction between 2 and 10 K. We identify the resistive, capacitive, and inductive contributions to the impedance. The equivalent inductance, obtained from fits to experimental data, drops drastically with increasing temperature, as the bulk starts to control electrical conduction. Self–sustained voltage oscillations, observed below 6 K across small crystals when biased with a dc current, point to a large SmB6 self–capacitance, likely brought by the surface states.