Project A07: Physical Review Letter 2017

Parametric Oscillation, Frequency Mixing, and Injection Locking of Strongly Coupled Nanomechanical Resonator Modes

Enforcing discipline on nanomechanical vibration

When one strongly shakes a pendulum close to its resonance frequency, it eventually locks to the shaking, i.e. tightly follows the applied force. Here we investigate such phenomena for two orthogonal vibrations of a nanomechanical string resonator which is five hundred times smaller than a human hair and embedded in an all...

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Project A01: Physical Review 2017 (Editors' Suggestion)

Acoustic waves undetectable by transient reflectivity measurements

In laser ultrasonics, ultrashort light pulses generate coherent acoustic pulses of picosecond duration via multiple possible physical mechanisms, involving optoacoustic conversion processes. These wide-band GHz acoustic signals are optically detected at the sample surfaces by ultrafast time-delayed probe light pulses. When the coherent acoustic pulses in GaAS are detected via the Brillouin scattering of probe light pulses of 400...

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Project A07: New Journal of Physics 2017

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 investigate finite-time effects in Stückelberg interferometry and discuss the exact analytical solution of the double passage Stückelberg problem by expanding the finite-time solution of the Landau–Zener problem. Approximating the return probability amplitudes of the...

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Project C04: Nature Communincations 2017

Correlation Driven Transport Asymmetries Through Coupled Spins in a Tunnel Junction

Spin–spin correlations are fundamental to many material properties because they favor certain ground states and are key in numerous models that describe the behavior of strongly correlated materials. While the sum of collective correlations usually lead to a macroscopically measurable change in properties, a direct quantification of correlations in atomic scale systems is difficult.
Using a scanning tunneling...

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Project C13/C14 - Chem. Eur. Journal

Redox-Active Tetraruthenium Macrocycles Built from 1,4-Divinylphenylene-Bridged Diruthenium Complexes

Metallamacrocylic tetraruthenium complexes were generated by treatment of 1,4-divinylphenylene-bridged diruthenium complexes with functionalized 1,3-benzene dicarboxylic acids and characterized by HR ESI-MS and multinuclear NMR spectroscopy. Every divinylphenylene diruthenium subunit is oxidized in two consecutive one-electron steps with half-wave potential splittings in the range of 250 to 330...

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Project B08: Nature Photonics 2017

Sub-cycle optical phase control of nanotunnelling in the single-electron regime

The high peak electric fields provided by single-cycle light pulses can be harnessed to manipulate and control charge motion in solid-state systems, resulting in electron emission out of metals and semiconductors or high harmonics generation in dielectrics. These processes are of a non-perturbative character and require precise reproducibility of the electric-field profile.
Here, we vary the carrier-envelope phase of...

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Project B02: Nano Letters 2016

Coupling of Excitons and Discrete Acoustic Phonons in Vibrationally Isolated Quantum Emitters

The photoluminescence emission by mesoscopic condensed matter is ultimately dictated by the fine-structure splitting of the fundamental exciton into optically allowed and dipole-forbidden states. In epitaxially grown semiconductor quantum dots, nonradiative equilibration between the fine-structure levels is mediated by bulk acoustic phonons, resulting in asymmetric spectral broadening of the excitonic...

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Project B02: ACS Macro Letters 2016

CdSe/CdS—conjugated polymer core–shell hybrid nanoparticles by a grafting-from approach

Hybrid particles consisting of II–VI semiconductor quantum dots and conjugated polymers are increasingly relevant, but access is limited by the usual step-growth nature of polymer formation. We report on a grafting-from approach by controlled Pd(II)-mediated polymerization to yield CdSe/CdS nanocrystals with a defined number of polyfluorene chains grown from their surface, as concluded from MALDI-TOF...

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Project B06 - Physical Review 2016

Long-range photon-mediated gate scheme between nuclear spin qubits in diamond

Defect centers in diamond are exceptional solid-state quantum systems that can have exceedingly long electron and nuclear spin coherence times. So far, single-qubit gates for the nitrogen nuclear spin, a two-qubit gate with a nitrogen-vacancy (NV) center electron spin, and entanglement between nearby nitrogen nuclear spins have been demonstrated.
Here, we develop a scheme to implement a universal two-qubit gate...

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Project A01 - J. Appl. Phys. 2016

Finite element analysis of surface modes in phononic crystal waveguides

The study of surface modes in phononic crystal waveguides in the hypersonic regime is a burgeoning field with a large number of possible applications. By using the finite element method, the band structure and the corresponding transmission spectrum of surface acoustic waves in phononic crystal waveguides generated by line defects in a silicon pillar-substrate system were calculated and investigated.
The bandgaps are caused...

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