nn0c03167_si_001.pdf (981.47 kB)
Enhanced Molecular Spin-Photon Coupling at Superconducting Nanoconstrictions
journal contribution
posted on 2020-06-01, 13:07 authored by Ignacio Gimeno, Wenzel Kersten, María C. Pallarés, Pablo Hermosilla, María José Martínez-Pérez, Mark D. Jenkins, Andreas Angerer, Carlos Sánchez-Azqueta, David Zueco, Johannes Majer, Anabel Lostao, Fernando LuisWe
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 Neff 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 Neff ranging between 2 × 106 and 1012 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 Neff. 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.