# Towards atomically-thin regime in bulk 4H-NbSe2 with interlayer disorder

## TL;DR

This paper explores how layer disorder in 4H-NbSe2 affects its electronic properties, mimicking those of atomically thin materials.

## Contribution

The study reveals that interlayer disorder in 4H-NbSe2 enhances resistivity anisotropy and superconducting properties.

## Key findings

- 4H-NbSe2 exhibits highly disordered layer stacking, reducing interlayer coherence.
- The disorder increases resistivity anisotropy and the superconducting upper critical field compared to 2Ha-NbSe2.
- Layer disorder in 4H-NbSe2 promotes quasi-two-dimensional electronic behavior in bulk crystals.

## Abstract

Polytypism in transition metal dichalcogenides (TMDs) introduces an additional degree of freedom for tailoring the electronic properties of layered van der Waals materials. Polytypes with larger unit cells, spanning four or six layers, can be viewed as natural homostructures, since their atomic composition remains identical across the layers. The resultant crystalline environments can potentially give rise to exotic electronic states, earning these materials recent attention. In this study, we examine structural and charge transport properties of metallic and superconducting 4Ha-NbSe2. We find that the compound has a highly disordered stacking of layers, which impedes interlayer coherence, as demonstrated by detailed out-of-plane resistivity measurements, and effectively tunes the bulk system towards an atomically thin limit. The disordered structure largely accounts for the enhanced resistivity anisotropy and superconducting upper critical field, when compared to 2Ha-NbSe2. This phenomenon can be exploited to promote quasi-two-dimensional physics in bulk crystals, and our study also underscores the importance of thorough structural characterization when investigating large-unit-cell polytypes of TMDs.