arXiv subjects

Srisaran Venkatachalam

Publications and source records attributed to Srisaran Venkatachalam.

5 recordsLinked to original sources

arXiv2024

Imaging nanomechanical vibrations and manipulating parametric mode coupling via scanning microwave microscopy

In this study, we present a novel platform based on scanning microwave microscopy for manipulating and detecting tiny vibrations of nanoelectromechanical resonators using a single metallic tip. The tip is placed on the top of a grounded silicon nitride membrane, acting as a movable top gate of the coupled resonator. We demonstrate its ability to map mechanical modes and investigate mechanical damping effects in a capacitive coupling scheme, based on its spatial resolution. We also manipulate the energy transfer coherently between the mode of the scanning tip and the underlying silicon nitride membrane, via parametric coupling. Typical features of optomechanics, such as anti-damping and electromechanically induced transparency, have been observed. Since the microwave optomechanical technology is fully compatible with quantum electronics and very low temperature conditions, it should provide a powerful tool for studying phonon tunnelling between two spatially separated vibrating elements, which could potentially be applied to quantum sensing.

physics.app-ph↗

arXiv2022

Stochastic switching and squeeze of hysteresis window in nonlinear responses of silicon nitride membrane nanoelectromechanical resonators

In this work, we present the effects of stochastic force generated by white noise on the nonlinear dynamics of a circular silicon nitride membrane. By tuning the membrane to the Duffing nonlinear region, detected signals switching between low- and high- amplitudes have been observed. They are generated by noise-assisted random jumps between bistable states at room temperature and exhibit high sensitivity to the driving frequency. Through artificially heating different mechanical vibration modes by external input of white noise, the switching rate exhibits exponential dependence on the effective temperature and follows with Kramer's law. Furthermore, both the measured switching rate and activation energy exhibit sensitivity to the width of the hysteresis window in nonlinear response and the driving force, which is in qualitative agreement with the theoretical descriptions. Besides, white noise-induced hysteresis window squeezing and bifurcation point shifting have also been observed, which are attributed to the stochastic force modulation of the spring constant of the membrane. These studies are essential for the generation and manipulation of stochastic switching effects, paving the way to explore new functions based on probability distributions in nanomechanical resonators.

physics.app-ph↗

arXiv2022

Capacitively coupled distinct mechanical resonators for room temperature phonon-cavity electromechanics

Coupled electromechanical resonators that can be independently driven/detected and easily integrated with external circuits are essential for exploring mechanical modes based signal processing. Here, we present a room temperature phonon-cavity electromechanical system, consisting of two distinct resonators: a silicon nitride electromechanical drum capacitively coupled to an aluminum one. We demonstrate electromechanically induced transparency and amplification in a two-tone driving scheme and observe the phonon-cavity force affecting the mechanical damping rates of both movable objects. We also develop an analytical model based on linearly coupled motion equations, which captures the optomechanical features in the classical limit and enables to fit quantitatively our measurements. Our results open up new possibilities in the study of phonon-cavity based signal processing in the classical and potentially in the future in the quantum regimes.

cond-mat.mes-hall↗

arXiv2021

Microwave optomechanical measurement of non-metallized SiN strings at mK temperatures

The mechanical properties of amorphous materials (glasses) at low temperatures are dominated by effects of low energy excitations that are thought to be atomic-scale tunneling two level systems (TTLS). In nanometer-scale glass samples, the temperature dependence of the sound speed and dissipation is modified relative to that of bulk glass samples. In addition to this size effect, the usual presence of a polycrystalline metal in nanomechanical resonators leads to a further departure from the well-studied behavior of insulating bulk glass. We report a dual chip optomechanical measurement technique used to characterize non-metallized amorphous SiN strings at low temperatures. A harp consisting of SiN strings of width 350 nm and lengths 40 to 80 $μ$m is coupled to an Al superconducting microwave cavity on a separate chip. The strings are driven dielectrically and their motion is detected via its modulation of the microwave resonance frequency.

cond-mat.mes-hall↗

arXiv2021

High-Q silicon nitride drum resonators strongly coupled to gates

Silicon nitride (SiN) mechanical resonators with high quality mechanical properties are attractive for fundamental research and applications. However, it is challenging to maintain these mechanical properties while achieving strong coupling to an electrical circuit for efficient on-chip integration. Here, we present a SiN drum resonator covered with an aluminum thin film, enabling large capacitive coupling to a suspended top-gate. Implementing the full electrical measurement scheme, we demonstrate a high quality factor ~ 1E4 (comparable to that of bare drums at room temperature) and present our ability to detect ? 10 mechanical modes at low temperature. The drum resonator is also coupled to a microwave cavity, so that we can perform optomechanical sideband pumping with a fairly good coupling strength G and demonstrate mechanical parametric amplification. This SiN drum resonator design provides efficient electrical integration and exhibits promising features for exploring mode coupling and signal processing.

physics.app-ph↗