Superconducting Two-Dimensional Metal-Organic Framework

TL;DR

This paper predicts superconductivity in organic metal-organic frameworks, specifically Cu-BHT, with higher critical temperatures in 2D monolayers compared to bulk, revealing new mechanisms for 2D organic superconductors.

Contribution

It introduces the first prediction of superconductivity in 2D organic metal-organic frameworks using first-principles calculations, highlighting a novel out-of-plane vibrational mechanism for T_c enhancement.

Findings

Cu-BHT is a BCS superconductor with T_c of 4.43 K in monolayer form.

Monolayer Cu-BHT has higher T_c than bulk, which is 1.58 K.

T_c enhancement is due to out-of-plane soft-mode vibrations, not interfacial effects.

Abstract

Superconductivity is a fascinating quantum phenomenon characterized by zero electrical resistance and the Meissner effect. To date, several distinct families of superconductors (SCs) have been discovered. These include three-dimensional (3D) bulk SCs in both inorganic and organic materials as well as two-dimensional (2D) thin film SCs but only in $inorganic$ materials. Here we predict superconductivity in 2D and 3D $organic$ metal-organic frameworks by using first-principles calculations. We show that the highly conductive and recently synthesized Cu-benzenehexathial (BHT) is a Bardeen-Cooper-Schrieffer SC. Remarkably, the monolayer Cu-BHT has a critical temperature ($T_{c}$) of 4.43 K while $T_{c}$ of bulk Cu-BHT is 1.58 K. Different from the enhanced $T_{c}$ in 2D inorganic SCs which is induced by interfacial effects, the $T_{c}$ enhancement in this 2D organic SC is revealed to be the out-of-plane soft-mode vibrations, analogous to surface mode enhancement originally proposed by $Ginzburg$. Our findings not only shed new light on better understanding 2D superconductivity, but also open a new direction to search for SCs by interface engineering with organic materials.