Enhancing the superconducting transition temperature of BaSi2 by structural tuning

TL;DR

This study combines experimental and theoretical approaches to demonstrate that flattening silicon sheets in BaSi2 enhances its superconducting transition temperature from 4 K to 8.7 K, revealing a structural tuning mechanism.

Contribution

It introduces a method to increase Tc in BaSi2 by controlling silicon sheet buckling, supported by ab-initio calculations.

Findings

Superconducting Tc increased from 4 K to 8.7 K with structural tuning.

Buckling of silicon sheets significantly affects electronic and phononic properties.

Structural control can be used to tune superconductivity in layered materials.

Abstract

We present a joint experimental and theoretical study of the superconducting phase of the layered binary silicide BaSi2. Compared with the layered AlB2 structure of graphite or diboride-like superconductors, in the hexagonal structure of binary silicides the sp3 arrangement of silicon atoms leads to corrugated sheets. Through a high-pressure synthesis procedure we are able to modify the buckling of these sheets, obtaining the enhancement of the superconducting transition temperature from 4 K to 8.7 K when the silicon planes flatten out. By performing ab-initio calculations based on density functional theory we explain how the electronic and phononic properties of the system are strongly affected by changes in the buckling. This mechanism is likely present in other intercalated layered superconductors, opening the way to the tuning of superconductivity through the control of internal structural parameters.