8 research outputs found
Nano-acoustic resonator with ultralong phonon lifetime
The energy damping time in a mechanical resonator is critical to many precision metrology applications, such as timekeeping and force measurements. We present measurements of the phonon lifetime of a microwave-frequency, nanoscale silicon acoustic cavity incorporating a phononic bandgap acoustic shield. Using pulsed laser light to excite a colocalized optical mode of the cavity, we measured the internal acoustic modes with single-phonon sensitivity down to millikelvin temperatures, yielding a phonon lifetime of up to τ_(ph,0) ≈ 1.5 seconds (quality factor Q = 5 × 10¹⁰) and a coherence time of τ_(coh,0) ≈ 130 microseconds for bandgap-shielded cavities. These acoustically engineered nanoscale structures provide a window into the material origins of quantum noise and have potential applications ranging from tests of various collapse models of quantum mechanics to miniature quantum memory elements in hybrid superconducting quantum circuits
Nano-acoustic resonator with ultralong phonon lifetime
The energy damping time in a mechanical resonator is critical to many precision metrology applications, such as timekeeping and force measurements. We present measurements of the phonon lifetime of a microwave-frequency, nanoscale silicon acoustic cavity incorporating a phononic bandgap acoustic shield. Using pulsed laser light to excite a colocalized optical mode of the cavity, we measured the internal acoustic modes with single-phonon sensitivity down to millikelvin temperatures, yielding a phonon lifetime of up to τ_(ph,0) ≈ 1.5 seconds (quality factor Q = 5 × 10¹⁰) and a coherence time of τ_(coh,0) ≈ 130 microseconds for bandgap-shielded cavities. These acoustically engineered nanoscale structures provide a window into the material origins of quantum noise and have potential applications ranging from tests of various collapse models of quantum mechanics to miniature quantum memory elements in hybrid superconducting quantum circuits
Phononic bandgap nano-acoustic cavity with ultralong phonon lifetime
We present measurements at millikelvin temperatures of the
microwave-frequency acoustic properties of a crystalline silicon nanobeam
cavity incorporating a phononic bandgap clamping structure for acoustic
confinement. Utilizing pulsed laser light to excite a co-localized optical mode
of the nanobeam cavity, we measure the dynamics of cavity acoustic modes with
single-phonon sensitivity. Energy ringdown measurements for the fundamental
5 GHz acoustic mode of the cavity shows an exponential increase in phonon
lifetime versus number of periods in the phononic bandgap shield, increasing up
to τ_(ph,0) ≈ 1.5~seconds. This ultralong lifetime, corresponding to an
effective phonon propagation length of several kilometers, is found to be
consistent with damping from non-resonant two-level system defects on the
surface of the silicon device. Potential applications of these ultra-coherent
nanoscale mechanical resonators range from tests of various collapse models of
quantum mechanics to miniature quantum memory elements in hybrid
superconducting quantum circuits
Dynamic Hosts for High-Performance Li–S Batteries Studied by Cryogenic Transmission Electron Microscopy and in Situ X‑ray Diffraction
Developing
a high-performance sulfur host is central to the commercialization
and general development of lithium–sulfur batteries. Here,
for the first time, we propose the concept of dynamic hosts for lithium–sulfur
batteries and elucidate the mechanism through which TiS<sub>2</sub> acts in such a fashion, using in situ X-ray diffraction and cryogenic
scanning transmission electron microscopy (cryo-STEM). A TiS<sub>2</sub>–S composite electrode delivered a reversible capacity of
1120 mAh g<sup>–1</sup> at 0.3 C after 200 cycles with a capacity
retention of 97.0% and capacities of 886 and 613 mAh g<sup>–1</sup> at 1.0 C up to 200 and 1000 cycles, respectively. Our results indicate
that it is Li<sub><i>x</i></sub>TiS<sub>2</sub> (0 < <i>x</i> ≤ 1), rather than TiS<sub>2</sub>, that effectively
traps polysulfides and catalytically decomposes Li<sub>2</sub>S