# Transport phenomena in a free-standing two-dimensional sodium sheet

## TL;DR

This study predicts that 2D sodium is a thermodynamically stable material with unique electronic transport properties, including high electrical and thermal conductivity, making it promising for future device applications.

## Contribution

First-principles calculations demonstrate that 2D Na is stable and exhibits distinctive transport properties, expanding the family of 2D materials with potential electronic applications.

## Key findings

- Intrinsic resistivity of doped 2D Na is 1.4 times larger than graphene at room temperature.
- Electronic thermal conductivity of 2D Na exceeds that of bulk sodium at 300 K.
- Wiedemann-Franz law holds for 2D Na with a Lorenz number of 2.41×10^{-8} V^2/deg^2.

## Abstract

The advances in the growth techniques provide numerous scope to explore the possibilities of new 2D materials for potential applications. With the aid of first-principle calculations we show that 2D Na can be a new addition to the family of thermodynamically stable 2D materials for device applications. Not surprisingly, due to half-occupied $3s$ orbital 2D Na possesses the features of the 2D electron gas (2DEG). The transport properties are examined based on the accurate solution of Boltzmann transport equation. With practically tunable carrier density in 2D materials, the intrinsic electrical resistivity of electron doped 2D Na is $\sim$ 1.4 times larger than that of graphene and falls below the latter 450 K onwards. The Bloch-Gr\"uneisen temperature is almost constant at 50 K, independent of the type or density of the charge carriers. The electronic thermal conductivity of pure 2D Na is $\sim$ 1.24 times larger than that of its bulk counterpart at 300 K. The Wiedemann-Franz law stands tall in 2D Na with calculated Lorenz number 2.41 $\times 10^{-8} V^2/deg^2$ at room temperature. The transport mechanism presented here is expected to occur in all Na like systems with a clean Fermi surface.