# Giant spin-splitting and gap renormalization driven by trions in single-layer WS$_2$/h-BN heterostructures

## TL;DR

This study demonstrates that electron doping in single-layer WS$_2$/h-BN heterostructures causes giant spin-splitting and band gap renormalization due to trion formation, revealing tunable electronic and spintronic properties in 2D materials.

## Contribution

It reveals the significant impact of trions on spin-orbit splitting and band gap in 2D heterostructures, a novel insight into many-body effects in these systems.

## Key findings

- Giant renormalization of spin-orbit splitting from 430 meV to 660 meV.
- Band gap reduction of at least 325 meV upon doping.
- Trionic quasiparticles significantly influence electronic properties.

## Abstract

In two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), new electronic phenomena such as tunable band gaps and strongly bound excitons and trions emerge from strong many-body effects, beyond spin-orbit coupling- and lattice symmetry-induced spin and valley degrees of freedom. Combining single-layer (SL) TMDs with other 2D materials in van der Waals heterostructures offers an intriguing means of controlling the electronic properties through these many-body effects via engineered interlayer interactions. Here, we employ micro-focused angle-resolved photoemission spectroscopy (microARPES) and in-situ surface doping to manipulate the electronic structure of SL WS$_2$ on hexagonal boron nitride (WS$_2$/h-BN). Upon electron doping, we observe an unexpected giant renormalization of the SL WS$_2$ valence band (VB) spin-orbit splitting from 430~meV to 660~meV, together with a band gap reduction of at least 325~meV, attributed to the formation of trionic quasiparticles. These findings suggest that the electronic, spintronic and excitonic properties are widely tunable in 2D TMD/h-BN heterostructures, as these are intimately linked to the quasiparticle dynamics of the materials.