Nanoscale real-time detection of quantum vortices at millikelvin temperatures

Abstract

Since we still lack a theory of classical turbulence, attention has focused on the conceptually simpler turbulence in quantum fluids. Reaching a better understanding of the quantum case may provide additional insight into the classical counterpart. That said, we have hitherto lacked detectors capable of the real-time, non-invasive probing of the wide range of length scales involved in quantum turbulence. Here we demonstrate the real-time detection of quantum vortices by a nanoscale resonant beam in superfluid 4He at 10 mK. Essentially, we trap a single vortex along the length of a nanobeam and observe the transitions as a vortex is either trapped or released, detected through the shift in the beam resonant frequency. By exciting a tuning fork, we control the ambient vortex density and follow its influence on the vortex capture and release rates demonstrating that these devices are capable of probing turbulence on the micron scale.

Dimensional control of tunneling two-level systems in nanoelectromechanical resonators

“…We have studied the intrinsic damping mechanisms in magnetomotively driven aluminum nanomechanical resonators of various sizes at millikelvin temperatures. The resonators can be used as ultrasensitive sensors in a wide range of applications, e.g., in studying superfluids [13,49] including quantized vortices [12], and the correct interpretation of the results requires a good understanding of the underlying device properties. The most significant mechanisms are found to be the damping due to the TTLSs and the magnetomotive damping.…”

“…Micro-and nanoelectromechanical systems (MEMS and NEMS, respectively) are also emerging in studies of the superfluids 3 He and 4 He [3][4][5][6][7][8][9], where they hold promise for superior sensitivity and spatial resolution over the immersed quartz tuning forks [10] and vibrating wires [11] routinely used in cryogenic research. Measuring the dynamics of a single quantized vortex in the superfluids is feasible with NEMS resonators [12,13]. Detailed analysis of such high-precision measurements requires a thorough understanding of the intrinsic damping mechanisms of the devices.…”

Fully suspended nano-beams for quantum fluids

“…Currently, a broad variety of devices has already been implemented to probe quantum liquids down to ultra-low temperatures. Restricting the discussion to mechanical objects immersed in the fluids, one can cite: microspheres [6], vibrating wires [7,8], quartz tuning forks [9][10][11], microelectromechanical (MEMS) [12] and nanoelectromechanical (NEMS) [13][14][15][16] systems. All of these tools have their advantages and disadvantages.…”

“…When making a suspended beam NEMS device on a chip, there is in practice a finite distance to the underlying substrate [13][14][15][16]. This means that the moving sensor can couple to the chip surface through the fluid it is probing: a finite size effect that can be relevant (or even dominant), depending on the fluid characteristics.…”

Dimensional control of tunneling two level systems in nanoelectromechanical resonators

“…Micro-and nanoelectromechanical systems (MEMS and NEMS, respectively) are also emerging in studies of the superfluids 3 He and 4 He [3][4][5][6][7][8][9], where they hold promise for superior sensitivity and spatial resolution over the immersed quartz tuning forks [10] and vibrating wires [11] routinely used in cryogenic research. Measuring the dynamics of a single quantized vortex in the superfluids is feasible with the NEMS resonators [12,13]. Detailed analysis of such high-precision measurements require thorough understanding of the intrinsic damping mechanisms of the devices.…”