# Quantum Oscillations of Electrical Resistivity in an Insulator

## TL;DR

This paper reports the discovery of quantum oscillations in the electrical resistivity of the insulator YbB12, indicating the presence of a Fermi surface and strongly correlated electrons despite its insulating behavior.

## Contribution

It demonstrates that an insulator can exhibit quantum oscillations typically associated with metals, revealing a bipartite ground state with both insulating and metallic properties.

## Key findings

- Quantum oscillations observed in YbB12 resistivity.
- Resistivity oscillations follow Fermi liquid temperature dependence.
- Presence of large effective masses indicating strongly correlated electrons.

## Abstract

In metals, orbital motions of conduction electrons on the Fermi surface are quantized in magnetic fields, which is manifested by quantum oscillations in electrical resistivity. This Landau quantization is generally absent in insulators. Here we report a notable exception in an insulator, ytterbium dodecaboride (YbB12). Despite much larger than that of metals, the resistivity of YbB12 exhibits profound quantum oscillations. This unconventional oscillation is shown to arise from the insulating bulk, yet the temperature dependence of their amplitude follows the conventional Fermi liquid theory of metals. The large effective masses indicate the presence of Fermi surface consisting of strongly correlated electrons. Our result reveals a mysterious bipartite ground state of YbB12: it is both a charge insulator and a strongly correlated metal.