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Nanotube Mechanical Resonator, Spin, and Superfluidity

Periodic Reporting for period 3 - NaTuRe (Nanotube Mechanical Resonator, Spin, and Superfluidity)

Reporting period: 2020-01-01 to 2021-06-30

Mechanical resonators based on carbon nanotubes are truly exceptional sensors of mass and force. Our work focuses on nuclear magnetic resonance (NMR) and electron spin resonance (ESR) measurements on atoms and molecules using nanotube resonators. Our aim is to perform magnetic-resonance force microscopy in order to image individual nuclear spins. Achieving this objective will be an unprecedented success in magnetic resonance imaging (MRI). Another aim is to measure molecular electron spins in a regime where the magnetic noise of the environment is reduced to an unprecedented level in order to see whether nature can provide molecular electronic spins endowed with long dephasing time, a subject of great interest in quantum technology. Another direction of research is to use nanotube resonators as a completely new experimental approach to investigate helium superfluidity. We probe helium superfluidity adsorbed onto the suspended nanotube. NaTuRe is a highly-interdisciplinary project with possible implications in quantum science, opto-mechanics, nano-science, structural biology, and low-temperature physics.
We developed new methods for the detection of mechanical vibrations down to helium temperature. We report on an ultrasensitive scheme based on a RLC resonator and a low-temperature amplifier to detect nanotube vibrations. This enables us to measure nanotube mechanical resonators with an unpreceded level. We demonstrate 4.3zN/sqrt(Hz) force sensitivity, which is the best force sensitivity achieved thus far with a mechanical resonator. This a major advance towards the detection of individual nuclear spins.

We are developing a new process in order to fabricate a nanotube mechanical resonator bridging a superconducting radio-frequency coplanar wave-guide. This process consists in transferring a nanotube on top of a chip containing the wave-guide. This fabrication process is primordial for the detection of the electron spins of molecules adsorbed on the nanotube.

We realize the long-standing goal of using electrons to cool a resonator near the quantum regime. We achieve a population number of 4.6 quanta. The resonator is about 20% of the time in the quantum ground state. The cooling method is simple yet powerful. It consists in applying a DC current of electrons through a suspended carbon nanotube. We anticipate that this new cooling scheme will be used by many groups in the world because of its simplicity.

Carbon Nanotube resonators have shown to be excellent sensing devices for the study of new physical phenomena at the nanoscale (e.g. spin physics, quantum electron transport, surface science, and light-matter interaction). Superfluid helium is known as a great system for the study of phase transitions, in particular for understanding transitions in two and three dimensions. By combining these two systems, it is possible to study various phenomena at the nanoscale, such as adsorption, supersolidity and superfluidity. We were able to build helium superfluid films with a number of atomic layers in a perfectly controlled manner. These helium multilayers adsorbed on a nanotube are of unprecedented quality compared to previous works. Such findings could open a new pathway into the field of topological phase transitions, aiming to carry out novel research of quantum fluids and solids in reduced geometry.
We have developed a new protocol to couple resonantly nuclear spins and nanotube mechanical vibrations. We are running experiments to see whether this protocol may allow us to detect single nuclear spins.

We are fabricating devices where a nanotube mechanical resonator is bridging a superconducting radio-frequency coplanar wave-guide. This fabrication process is primordial for the detection of the electron spins of molecules adsorbed on the nanotube.

The new devices and the new detection methods that we developed within this project are fantastic. It enables us to study the electron-vibration coupling in a completely new way. For this reason, we will be able to study electron-phonon interaction in regimes that have never been explored thus far.