155 research outputs found
Electromechanically induced absorption in a circuit nano-electromechanical system
A detailed analysis of electromechanically induced absorption (EMIA) in a
circuit nano-electromechanical hybrid system consisting of a superconducting
microwave resonator coupled to a nanomechanical beam is presented. By
performing two-tone spectroscopy experiments we have studied EMIA as a function
of the drive power over a wide range of drive and probe tone detunings. We find
good quantitative agreement between experiment and theoretical modeling based
on the Hamiltonian formulation of a generic electromechanical system. We show
that the absorption of microwave signals in an extremely narrow frequency band
(\Delta\omega/2\pi <5 Hz) around the cavity resonance of about 6 GHz can be
adjusted over a range of more than 25 dB on varying the drive tone power by a
factor of two. Possible applications of this phenomenon include notch filters
to cut out extremely narrow frequency bands (< Hz) of a much broader band of
the order of MHz defined by the resonance width of the microwave cavity. The
amount of absorption as well as the filtered frequency is tunable over the full
width of the microwave resonance by adjusting the power and frequency of the
drive field. At high drive power we observe parametric microwave amplification
with the nanomechanical resonator. Due to the very low loss rate of the
nanomechanical beam the drive power range for parametric amplification is
narrow, since the beam rapidly starts to perform self-oscillations.Comment: 16 pages, 5 figure
Determination of effective mechanical properties of a double-layer beam by means of a nano-electromechanical transducer
We investigate the mechanical properties of a doubly-clamped, double-layer
nanobeam embedded into an electromechanical system. The nanobeam consists of a
highly pre-stressed silicon nitride and a superconducting niobium layer. By
measuring the mechanical displacement spectral density both in the linear and
the nonlinear Duffing regime, we determine the pre-stress and the effective
Young's modulus of the nanobeam. An analytical double-layer model
quantitatively corroborates the measured values. This suggests that this model
can be used to design mechanical multilayer systems for electro- and
optomechanical devices, including materials controllable by external parameters
such as piezoelectric, magnetrostrictive, or in more general multiferroic
materials.Comment: 4 pages, 4 figures, 1 supplemental materia
Solid-state magnetic traps and lattices
We propose and analyze magnetic traps and lattices for electrons in
semiconductors. We provide a general theoretical framework and show that
thermally stable traps can be generated by magnetically driving the particle's
internal spin transition, akin to optical dipole traps for ultra-cold atoms.
Next we discuss in detail periodic arrays of magnetic traps, i.e. magnetic
lattices, as a platform for quantum simulation of exotic Hubbard models, with
lattice parameters that can be tuned in real time. Our scheme can be readily
implemented in state-of-the-art experiments, as we particularize for two
specific setups, one based on a superconducting circuit and another one based
on surface acoustic waves.Comment: 18 pages, 8 figure
Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dots
We report on the development and testing of a coplanar stripline antenna that
is designed for integration in a magneto-photoluminescence experiment to allow
coherent control of individual electron spins confined in single self-assembled
semiconductor quantum dots. We discuss the design criteria for such a structure
which is multi-functional in the sense that it serves not only as microwave
delivery but also as electrical top gate and shadow mask for the single quantum
dot spectroscopy. We present test measurements on hydrogenated amorphous
silicon, demonstrating electrically detected magnetic resonance using the
in-plane component of the oscillating magnetic field created by the coplanar
stripline antenna necessary due to the particular geometry of the quantum dot
spectroscopy. From reference measurements using a commercial electron spin
resonance setup in combination with finite element calculations simulating the
field distribution in the structure, we obtain an average magnetic field of
~0.2mT at the position where the quantum dots would be integrated into the
device. The corresponding pi-pulse time of ~0.3us fully meets the requirements
set by the high sensitivity optical spin read-out scheme developed for the
quantum dot
Electrically detected magnetic resonance using radio-frequency reflectometry
The authors demonstrate readout of electrically detected magnetic resonance
at radio frequencies by means of an LCR tank circuit. Applied to a silicon
field-effect transistor at milli-kelvin temperatures, this method shows a
25-fold increased signal-to-noise ratio of the conduction band electron spin
resonance and a higher operational bandwidth of > 300 kHz compared to the kHz
bandwidth of conventional readout techniques. This increase in temporal
resolution provides a method for future direct observations of spin dynamics in
the electrical device characteristics.Comment: 9 pages, 3 figure
Observation of extremely slow hole spin relaxation in self-assembled quantum dots
We report the measurement of extremely slow hole spin relaxation dynamics in
small ensembles of self-assembled InGaAs quantum dots. Individual spin
orientated holes are optically created in the lowest orbital state of each dot
and read out after a defined storage time using spin memory devices. The
resulting luminescence signal exhibits a pronounced polarization memory effect
that vanishes for long storage times. The hole spin relaxation dynamics are
measured as a function of external magnetic field and lattice temperature. We
show that hole spin relaxation can occur over remarkably long timescales in
strongly confined quantum dots (up to ~270 us), as predicted by recent theory.
Our findings are supported by calculations that reproduce both the observed
magnetic field and temperature dependencies. The results suggest that hole spin
relaxation in strongly confined quantum dots is due to spin orbit mediated
phonon scattering between Zeeman levels, in marked contrast to higher
dimensional nanostructures where it is limited by valence band mixing.Comment: Published by Physical Review
Electrically-detected magnetic resonance in ion-implanted Si:P nanostructures
We present the results of electrically-detected magnetic resonance (EDMR)
experiments on silicon with ion-implanted phosphorus nanostructures, performed
at 5 K. The devices consist of high-dose implanted metallic leads with a square
gap, into which Phosphorus is implanted at a non-metallic dose corresponding to
10^17 cm^-3. By restricting this secondary implant to a 100 nm x 100 nm region,
the EDMR signal from less than 100 donors is detected. This technique provides
a pathway to the study of single donor spins in semiconductors, which is
relevant to a number of proposals for quantum information processing.Comment: 9 pages, 3 figure
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
Phosphorus donors in highly strained silicon
The hyperfine interaction of phosphorus donors in fully strained Si thin
films grown on virtual SiGe substrates with is
determined via electrically detected magnetic resonance. For highly strained
epilayers, hyperfine interactions as low as 0.8 mT are observed, significantly
below the limit predicted by valley repopulation. Within a Green's function
approach, density functional theory (DFT) shows that the additional reduction
is caused by the volume increase of the unit cell and a local relaxation of the
Si ligands of the P donor.Comment: 12 pages, 3 figure
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