# Dual quantum confinement and anisotropic spin splitting in the multi-valley semimetal PtSe$_2$

## TL;DR

This study reveals how quantum well states and anisotropic spin splittings form at the surface of the semimetal PtSe₂, influenced by complex band bending and carrier types, offering new insights into surface electronic structures.

## Contribution

It demonstrates the formation of multiple Fermi surfaces with anisotropic Rashba-like spin splittings and the impact of non-monotonic band bending in a semimetal surface.

## Key findings

- Multiple Fermi surfaces with anisotropic spin splitting observed.
- Non-monotonic band bending with electron and hole regions identified.
- Enhanced spin splitting due to spatially-segregated carriers.

## Abstract

We investigate the electronic structure of a two-dimensional electron gas created at the surface of the multi-valley semimetal 1T-PtSe$_2$. Using angle-resolved photoemission and first-principles-based surface space charge calculations, we show how the induced quantum well subband states form multiple Fermi surfaces which exhibit highly anisotropic Rashba-like spin splittings. We further show how the presence of both electron- and hole-like bulk carriers causes the near-surface band bending potential to develop an unusual non-monotonic form, with spatially-segregated electron accumulation and hole accumulation regions, which in turn amplifies the induced spin splitting. Our results thus demonstrate the novel environment that semimetals provide for tailoring electrostatically-induced potential profiles and their corresponding quantum subband states