Enhanced Molecular Spin-Photon Coupling at Superconducting Nanoconstrictions

Abstract

We combine top-down and bottom-up nanolithography to optimize the coupling of small molecular spin ensembles to 1.4 GHz on-chip superconducting resonators. Nanoscopic constrictions, fabricated with a focused ion beam at the central transmission line, locally concentrate the microwave magnetic field. Drops of free-radical molecules have been deposited from solution onto the circuits. For the smallest ones, the molecules were delivered at the relevant circuit areas by means of an atomic force microscope. The number of spins N eff effectively coupled to each device was accurately determined combining Scanning Electron and Atomic Force Microscopies. The collective spin-photon coupling constant has been determined for samples with N eff ranging between 2 × 10 6 and 10 12 spins, and for temperatures down to 44 mK. The results show the well-known collective enhancement of the coupling proportional to the square root of N eff . The average coupling of individual spins is enhanced by more than 4 orders of magnitude (from 4 mHz up to above 180 Hz), when the transmission line width is reduced from 400 μm down to 42 nm, and reaches maximum values near 1 kHz for molecules located on the smallest nanoconstrictions.

A dissymmetric [Gd2] coordination molecular dimer hosting six addressable spin qubits

“…These difficulties can possibly be overcome by synthesizing well-organized molecular frameworks, in which all molecules need to be oriented in the same manner and, at the same time, magnetically diluted or sufficiently far away from each other [48][49][50] . In the end, the ideal situation would be to explore the response of individual molecules, either via the application of single-molecule electronics 24,25,28 or by enhancing the current sensitivity of magnetic spectroscopic techniques [51][52][53][54] .…”

Barrier-free reverse-intersystem crossing in organic molecules by strong light-matter coupling

“…Strong light-matter coupling has emerged as a new tool for tailoring molecular properties without touching the chemical structure 8 , 9 . The formed hybrid states, referred to as polaritons, play key roles in modifying the photophysical and photochemical processes in the strong coupling regime 10 – 13 , such as the enhancement of Förster type and vibrational energy transfer 14 – 17 , tilting the ground-state reactivity landscape 18 , 19 , facilitating Bose–Einstein condensation and organic lasing 20 – 25 , reducing energy losses in photovoltaics 26 – 29 , manipulating triplet state dynamics 30 – 33 , maximizing superconducting current 34 and optimization of artificial photosynthesis 35 . In particular, we have previously demonstrated polariton-enhanced RISC in optical cavities by reducing the energy gap between singlet (polariton) and triplet states 36 , the method of which was then adopted to achieve an energy inversion of the two states 37 .…”

Storage and retrieval of microwave pulses with molecular spin ensembles

“…The magnetic coupling and the integration of molecular spins into planar resonant geometries has been extensively investigated [24][25][26][27] . Moreover, the coherent coupling with MW photons has been recently achieved using transition metal-based oxovanadium(IV) complexes 28,29 , as well as organic radicals [29][30][31] embedded into planar resonant geometries, paving the way for the integration of molecular spin ensembles into microwave quantum architectures.…”