Signature of large-gap quantum spin Hall state in the layered mineral jacutingaite

Quantum spin Hall (QSH) insulators are materials that feature an insulating bulk and host edge states protected by time-reversal symmetry. The helical locking of spin and momentum in these states suppresses backscattering of charge carriers, promising applications from low-power electronics to quantum computing. A major challenge for applications is the identification of large gap QSH materials, which would enable room temperature dissipationless transport in their edge states. Here we show that the layered mineral jacutingaite (Pt$_2$HgSe$_3$) is a candidate QSH material, realizing the long sought after the Kane-Mele insulator. Using scanning tunneling microscopy, we measure a band gap of 110 meV, above room temperature, and identify the hallmark edge states. By calculating the $\mathbb{Z}_2$ invariant, we confirm the topological nature of the gap. Being a layered mineral, it is stable in air and can be thinned down to a few atomic layers by mechanical exfoliation. Furthermore, we demonstrate that it can be integrated into heterostructures with other two-dimensional materials. This adds a topological insulator to the 2D quantum material library, greatly expanding the possibilities for tuning 2D electron systems using stacks of layered materials.