Ultralow-loss diamond nanomechanics enabled by van der Waals self-assembly

Achieving ultralow-loss mechanical system is central to quantum science and precision measurements, as dissipation inherently limits sensitivity by introducing fluctuations into measurement systems according to the fluctuation-dissipation theorem. A prominent example is application of crystalline mirror coatings in gravitational-wave detectors such as LIGO, where reducing thermal-mechanical noise significantly enhances detection precision. Nanomechanical oscillators have recently emerged as promising platforms for exploring macroscopic quantum phenomena and precision sensing. However, surface stiction intrinsic to nanoscale structures hinders the achievement of ultralow acoustic losses obtained via dissipation dilution in high-aspect-ratio structures. Here, we transform this longstanding obstacle into a robust solution for tension-enabled dissipation dilution, via a novel liquid assisted van der Waals (vdW) self-assembly method. Leveraging intrinsic nanoscale surface interactions, we achieve controlled tensile stresses up to 1.3 GPa in single-crystal diamond—an ideal but notoriously difficult material to strain-engineer—without introducing additional interface losses. We demonstrate mechanical quality factors exceeding 100 million and an estimated force sensitivity of S_F^1/2=0.5 aN/Hz^1/2 at 5 K, surpassing state-of-the-art systems at comparable aspect ratios. This versatile approach, broadly applicable to other crystalline materials, opens new avenues for ultra precise quantum sensing, tests of quantum gravity, and hybrid quantum systems.