Metasurface-Enhanced Terahertz Magnetic Resonance to Address Molecular Spin Qubits on Surfaces

• Applicant: Lorenzo Tesi, Ph.D.
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 529038510

Technological advances to access Terahertz (THz) frequencies are nowadays of crucial importance for ultra-fast communication, security scanners, identification of materials based on their fingerprint, investigation of molecular vibrations and magnetic excitations. For long time, the lack of efficient sources and detectors prevented to explore this frequency range where radiation-matter interaction is weak. A solution to this limitation was achieved by the realization of artificial (meta)materials able to interact with THz radiation. Among them, metasurfaces, arrays of subwavelength planar resonators, can control electromagnetic waves beyond natural responses, for example concentrating electric fields for ultra-high sensing applications. THz radiation can be used to excite magnetic transitions: THz electron spin resonance (THz ESR) is a powerful and versatile technique for investigating materials with unpaired electron spins that, compared to lower standard frequencies (9-35 GHz), allows a higher spectral resolution and the access to a wider range of materials and phenomena. However, the limited power of THz sources precludes THz ESR experiments on volume-limited samples, which seriously limits its application. The realization of metasurface resonators enhancing magnetic fields in a confined volume would greatly solve this sensitivity issue. The project aims to realize metasurface resonators (MRs) to localize THz magnetic fields in a two-dimensional area, thus allowing detection of volume-limited and thin film samples by THz ESR. Within the project, MRs will be designed, fabricated and exploited in magnetic resonance experiments. As a use case, we will focus on molecular spin qubits (MSQs). The enhanced sensitivity will be exploited to understand how the qubits properties change after deposition on surface, which is an essential step towards the realization of functional quantum devices. In the long term, magnetic metasurfaces will become a widespread tool for surface-sensitive magnetic resonance experiments covering a broad range of applications.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: Terahertz Time Domain Spectrometer ; Thermal Evaporation Chamber
• Instrumentation Group: 6380 Frequenzanalysatoren, Schwingungsanalysatoren ; 8330 Vakuumbedampfungsanlagen und -präparieranlagen für Elektronenmikroskopie