arXiv subjects

Maximilian J. Seitner

Publications and source records attributed to Maximilian J. Seitner.

9 recordsLinked to original sources

arXiv2016

Parametric oscillation, frequency mixing and injection locking of strongly coupled nanomechanical resonator modes

We study locking phenomena of two strongly coupled, high-quality factor nanomechanical resonator modes subject to a common parametric drive at a single drive frequency. By controlled dielectric gradient forces we tune the resonance frequencies of the flexural in-plane and out-of-plane oscillation of the high stress silicon nitride string through their mutual avoided crossing. For the case of the strong common parametric drive signal-idler generation via parametric oscillation is observed, analogously to the framework of nonlinear optical effects in an optical parametric oscillator. Frequency tuning of the signal and idler resonances is demonstrated. When the resonance frequencies of signal and idler get closer to each other, partial injection locking, injection pulling and complete injection locking to half of the drive frequency occurs depending on the pump strength. Furthermore, satellite resonances, symmetrically off-set from signal and idler by their beat-note, are observed which can be attributed to degenerate four-wave-mixing in the highly nonlinear mechanical oscillations.

cond-mat.mes-hall↗

arXiv2016

Finite time Stückelberg interferometry with nanomechanical modes

Stückelberg interferometry describes the interference of two strongly coupled modes during a double passage through an avoided energy level crossing. In this work, we experimentally investigate finite time effects in Stückelberg interference and provide an exact analytical solution of the Stückelberg problem. Approximating this solution in distinct limits reveals uncharted parameter regimes of Stückelberg interferometry. Experimentally, we study these regimes using a purely classical, strongly coupled nanomechanical two-mode system of high quality factor. The classical two-mode system consists of the in-plane and out-of-plane fundamental flexural mode of a high stress silicon nitride string resonator, coupled via electric gradient fields. The dielectric control and microwave cavity enhanced universal transduction of the nanoelectromechanical system allows for the experimental access to all theoretically predicted Stückelberg parameter regimes. We exploit our experimental and theoretical findings by studying the onset of Stückelberg interference in dependence of the characteristic system control parameters and obtain characteristic excitation oscillations between the two modes even without the explicit need of traversing the avoided crossing. The presented theory is not limited to classical mechanical two-mode systems but can be applied to every strongly coupled (quantum) two-level system, for example a spin-1/2 system or superconducting qubit.

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arXiv2016

Classical Stückelberg interferometry of a nanomechanical two-mode system at room temperature

The transition from classical to quantum mechanics has intrigued scientists in the past and remains one of the most fundamental conceptual challenges in state-of-the-art physics. Beyond the quantum mechanical correspondence principle, quantum-classical analogies have attracted considerable interest. In this work, we present classical two-mode interference for a nanomechanical two-mode system, realizing classical Stückelberg interferometry. In the past, Stückelberg interferometry has been investigated exclusively in quantum mechanical two-level systems. Here, we experimentally demonstrate a classical analog of Stückelberg interferometry taking advantage of coherent energy exchange between two-strongly coupled, high quality factor nanomechanical resonator modes. Furthermore, we provide an exact theoretical solution for the double passage Stückelberg problem which reveals the analogy of the return probabilities in the quantum mechanical and the classical version of the problem. This result qualifies classical two-mode systems at large as a testbed for quantum mechanical interferometry.

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arXiv2015

A universal platform for magnetostriction measurements in thin films

We present a universal nanomechanical sensing platform for the investigation of magnetostriction in thin films. It is based on a doubly-clamped silicon nitride nanobeam resonator covered with a thin magnetostrictive film. Changing the magnetization direction within the film plane by an applied magnetic field generates a magnetostrictive stress and thus changes the resonance frequency of the nanobeam. A measurement of the resulting resonance frequency shift, e.g. by optical interferometry, allows to quantitatively determine the magnetostriction constants of the thin film. We use this method to determine the magnetostriction constants of a 10nm thick polycrystalline cobalt film, showing very good agreement with literature values. The presented technique can be useful in particular for the precise measurement of magnetostriction in a variety of (conducting and insulating) thin films, which can be deposited by e.g. electron beam deposition, thermal evaporation or sputtering.

cond-mat.mes-hall↗

arXiv2014

Damping of metallized bilayer nanomechanical resonators at room temperature

We investigate the influence of gold thin-films subsequently deposited on a set of initially bare, doubly clamped, high-stress silicon nitride string resonators at room temperature. Analytical expressions for resonance frequency, quality factor and damping for both in- and out-of-plane flexural modes of the bilayer system are derived, which allows for the determination of effective elastic parameters of the composite structure from our experimental data. We find the inverse quality factor to scale linearly with the gold film thickness, indicating that the overall damping is governed by losses in the metal. Correspondingly, the mechanical linewidth increases by more than one order of magnitude compared to the bare silicon nitride string resonator. Furthermore, we extract mechanical quality factors of the gold film for both flexural modes and show that they can be enhanced by complete deposition of the metal in a single step, suggesting that surface and interface losses play a vital role in metal thin-films.

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arXiv2013

Signatures of two-level defects in the temperature-dependent damping of nanomechanical silicon nitride resonators

The damping rates of high quality factor nanomechanical resonators are well beyond intrinsic limits. Here, we explore the underlying microscopic loss mechanisms by investigating the temperature-dependent damping of the fundamental and third harmonic transverse flexural mode of a doubly clamped silicon nitride string. It exhibits characteristic maxima reminiscent of two-level defects typical for amorphous materials. Coupling to those defects relaxes the momentum selection rules, allowing energy transfer from discrete long wavelength resonator modes to the high frequency phonon environment.

cond-mat.mes-hall↗

arXiv2012

Coherent control of a nanomechanical two-level system

The Bloch sphere is a generic picture describing a coupled two-level system and the coherent dynamics of its superposition states under control of electromagnetic fields. It is commonly employed to visualise a broad variety of phenomena ranging from spin ensembles and atoms to quantum dots and superconducting circuits. The underlying Bloch equations describe the state evolution of the two-level system and allow characterising both energy and phase relaxation processes in a simple yet powerful manner. Here we demonstrate the realisation of a nanomechanical two-level system which is driven by radio frequency signals. It allows to extend the above Bloch sphere formalism to nanoelectromechanical systems. Our realisation is based on the two orthogonal fundamental flexural modes of a high quality factor nanostring resonator which are strongly coupled by a dielectric gradient field. Full Bloch sphere control is demonstrated via Rabi, Ramsey and Hahn echo experiments. This allows manipulating the classical superposition state of the coupled modes in amplitude and phase and enables deep insight into the decoherence mechanisms of nanomechanical systems. We have determined the energy relaxation time T1 and phase relaxation times T2 and T2*, and find them all to be equal. This not only indicates that energy relaxation is the dominating source of decoherence, but also demonstrates that reversible dephasing processes are negligible in such collective mechanical modes. We thus conclude that not only T1 but also T2 can be increased by engineering larger mechanical quality factors. After a series of ground-breaking experiments on ground state cooling and non-classical signatures of nanomechanical resonators in recent years, this is of particular interest in the context of quantum information processing.

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arXiv2012

Frequency and Q-factor control of nanomechanical resonators

We present an integrated scheme for dielectric drive and read-out of high-Q nanomechanical resonators which enables tuning of both the resonance frequency and quality factor with an applied DC voltage. A simple model for altering these quantities is derived, incorporating the resonator's complex electric polarizability and position in an inhomogeneous electric field, which agrees very well with the experimental findings as well as FEM simulations. By comparing two sample geometries we are able to show that careful electrode design can determine the direction of frequency tuning of flexural in- and out-of-plane modes of a string resonator. Furthermore we demonstrate that the mechanical quality factor can be voltage reduced more than fivefold.

cond-mat.mes-hall↗

arXiv2012

Non-adiabatic dynamics of two strongly coupled nanomechanical resonator modes

The Landau-Zener transition is a fundamental concept for dynamical quantum systems and has been studied in numerous fields of physics. Here we present a classical mechanical model system exhibiting analogous behaviour using two inversely tuneable, strongly coupled modes of the same nanomechanical beam resonator. In the adiabatic limit, the anticrossing between the two modes is observed and the coupling strength extracted. Sweeping an initialized mode across the coupling region allows mapping of the progression from diabatic to adiabatic transitions as a function of the sweep rate.

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