Magnetic molecule tunnel heterojunctions

TL;DR

This paper investigates magnetic molecule heterojunctions with CoPc films, revealing quantum tunneling and spin-related features crucial for quantum information devices.

Contribution

It provides the first detailed characterization of magnetic molecule heterojunctions with superconducting and tunneling properties, highlighting quantum effects.

Findings

Superconducting gap observed at 6 K.

Quantum tunneling confirmed through I-V characteristics.

Spin states influence differential conductance features.

Abstract

We characterize molecular magnet heterojunctions in which sublimated CoPc films as thin as 5 nm are sandwiched between transparent conducting bottom-layer indium tin oxide and top-layer soft-landing eutectic GaIn (EGaIn) electrodes. The roughness of the cobalt phthalocyanine (CoPc) films was determined by atomic force microscopy to be on the order of several nanometers, and crystalline ordering of lying-down planar molecules was confirmed by X-ray diffraction. The current-voltage (I-V) characteristics reveal the onset of a superconducting gap at Tc = 6 K, which together with higher temperature fits to a modified Simmons' model, provide incontrovertible evidence for direct quantum mechanical tunneling processes through the magnetic molecules in our heterojunctions. The voltage dependent features in the differential conductance measurements relate to spin states of single molecules or aggregates of molecules and should prove to be important for quantum information device development.