Observation of Yu–Shiba–Rusinov States and Inelastic Tunneling Spectroscopy for Intramolecule Magnetic Exchange Interaction Energy of Terbium Phthalocyanine (TbPc) Species Adsorbed on Superconductor NbSe₂

Abstract

We investigated the spin properties of the terbium phthalocyanine (TbPc) species adsorbed on the superconductor NbSe 2 surface using scanning tunneling microscopy and spectroscopy. TbPc 2 is a molecule in a class of single-molecule magnets (SMMs), and the use of superconductor electrodes attracts attention for the application to the devices using the spin degree of freedom. TbPc is a building block of TbPc 2 and can reveal the spin component’s behavior. In the experiment, TbPc species were placed on the surface of the superconductor NbSe 2 . We measured Yu–Shiba–Rusinov (YSR) states caused by the interaction between the superconducting state and magnetic impurity and inelastic tunneling spectroscopy (IETS) for the spin excitation, below 1 K. We also measured the Kondo state formed by the magnetic singlet formation. We detected the radical spin at the ligand position of the TbPc by the presence of the Kondo peak and demonstrated that the radical spin forms the YSR feature. In addition, the exchange interaction energy ( E ex ) between the spins of the radical ligand (Pc) and the center 4f metal atom (Tb 3+ ) is determined by using the IETS technique. E ex is a critical parameter that determines the blocking temperature, below which the sample behaves as an SMM. IETS results show that the statistical distribution of E ex has peaked at 1.3, 1.6, and 1.9 meV. The energy range is comparable to the recent theoretical calculation result. In addition, we show that the energy variation is correlated with the bonding configuration of TbPc.

Nanostructures as the Substrate for Single-Molecule Magnet Deposition

“…Consequently, it would be compelling to couple them with a preferred type of nanostructure, especially considering that studies have already demonstrated such coupling in the case of metallocene-SWCNT hybrids [ 228 ]. Here, the latest achievements by Komeda and co-workers, concerning the employment of superconducting NbSe substrates for TbPc molecules, are also worth mentioning, although the authors did not include information about the thickness of the used NbSe layer, which made it hard for us to consider it a nanostructure [ 229 , 230 ]. Nevertheless, the coupling of superconducting materials and SMMs seems to be a very appealing and promising route, the exploration of which should be continued.…”

Chirality‐Induced Spin Selectivity: An Enabling Technology for Quantum Applications

“…ii) Quantum gates iii) Chemical engineering of the Hamiltonian [ 7,8,13,30] [ [20][21][22][23] [ 27,31] iv) Quantum algorithms v) Embedded quantum error correction vi) Processability and hybrid structures [28] [ 17, [32][33][34] [ [35][36][37][38][39][40][41][42][43][44] Each column refers to a different achievement/capability. In the different rows, we report the experimental results/schemes, the related molecular structures, and the relevant references.…”

“…[34] Copyright 2022, American Chemical Society). vi) Processability into hybrid structures and organization onto metallic and superconducting surfaces, [35][36][37][38][39][40] tuning their coupling with the substrate, while keeping their magnetic properties and enabling manipulation of electronic [41] and nuclear spins. [42] Color code for molecular structures: C gray; N pale blue, O red, S yellow, V purple, Cu orange, Ni and Cr blue, Tb cyan, lanthanides in (v) green and white.…”

“…perspectives for integration in quantum networks. [50,51] Finally, molecular spins can be processed into hybrid structures and organized on surfaces [35][36][37][38][39][40]43] or within superconducting resonators. [41,42,44] In this context, spin-correlated radical pairs (RPs) generated by photoinduced electron transfer (PET) have also been proposed for quantum information, because of their natural existence in entangled Bell states and the possibility of achieving atomic-scale control and interaction with other degrees of freedom, such as photons, charges and phonons.…”

“…[ 32–34,48,49 ] The ingenious design of the electronic structure has also enabled a promising step toward optical initialization and readout of molecular spin qubits with interesting perspectives for integration in quantum networks. [ 50,51 ] Finally, molecular spins can be processed into hybrid structures and organized on surfaces [ 35–40,43 ] or within superconducting resonators. [ 41,42,44 ]…”