1,172 research outputs found
Fermionic topological quantum states as tensor networks
Tensor network states, and in particular projected entangled pair states, play an important role in the description of strongly correlated quantum lattice systems. They do not only serve as variational states in numerical simulation methods, but also provide a framework for classifying phases of quantum matter and capture notions of topological order in a stringent and rigorous language. The rapid development in this field for spin models and bosonic systems has not yet been mirrored by an analogous development for fermionic models. In this work, we introduce a tensor network formalism capable of capturing notions of topological order for quantum systems with fermionic components. At the heart of the formalism are axioms of fermionic matrix-product operator injectivity, stable under concatenation. Building upon that, we formulate a Grassmann number tensor network ansatz for the ground state of fermionic twisted quantum double models. A specific focus is put on the paradigmatic example of the fermionic toric code. This work shows that the program of describing topologically ordered systems using tensor networks carries over to fermionic models
Localization of bosonic atoms by fermionic impurities in a 3d optical lattice
We observe a localized phase of ultracold bosonic quantum gases in a
3-dimensional optical lattice induced by a small contribution of fermionic
atoms acting as impurities in a Fermi-Bose quantum gas mixture. In particular
we study the dependence of this transition on the fermionic 40K impurity
concentration by a comparison to the corresponding superfluid to Mott insulator
transition in a pure bosonic 87Rb gas and find a significant shift in the
transition parameter. The observed shift is larger than expected based on a
mean-field argument, which is a strong indication that disorder-related effects
play a significant role.Comment: 4 pages, 4 figure
Intensity interferometry of single x-ray pulses from a synchrotron storage ring
We report on measurements of second-order intensity correlations at the high
brilliance storage ring PETRA III using a prototype of the newly developed
Adaptive Gain Integrating Pixel Detector (AGIPD). The detector recorded
individual synchrotron radiation pulses with an x-ray photon energy of 14.4 keV
and repetition rate of about 5 MHz. The second-order intensity correlation
function was measured simultaneously at different spatial separations that
allowed to determine the transverse coherence length at these x-ray energies.
The measured values are in a good agreement with theoretical simulations based
on the Gaussian Schell-model.Comment: 16 pages, 6 figures, 42 reference
Miscellanea in the Brāhmī Script from the Berezovsky and Krotkov Collections (IOM, RAS) with an appendix: ВФ-4190
Descriptive and Comparative Linguistic
Ab initio and nuclear inelastic scattering studies of FeSi/GaAs heterostructures
The structure and dynamical properties of the FeSi/GaAs(001) interface
are investigated by density functional theory and nuclear inelastic scattering
measurements. The stability of four different atomic configurations of the
FeSi/GaAs multilayers is analyzed by calculating the formation energies and
phonon dispersion curves. The differences in charge density, magnetization, and
electronic density of states between the configurations are examined. Our
calculations unveil that magnetic moments of the Fe atoms tend to align in a
plane parallel to the interface, along the [110] direction of the FeSi
crystallographic unit cell. In some configurations, the spin polarization of
interface layers is larger than that of bulk FeSi. The effect of the
interface on element-specific and layer-resolved phonon density of states is
discussed. The Fe-partial phonon density of states measured for the FeSi
layer thickness of three monolayers is compared with theoretical results
obtained for each interface atomic configuration. The best agreement is found
for one of the configurations with a mixed Fe-Si interface layer, which
reproduces the anomalous enhancement of the phonon density of states below 10
meVComment: 14 pages, 9 figures, 4 table
Reflections in Systemic Family Psychotherapy and Adult Mental Health Services in the South East of Ireland; and beyond.
Systemic Family Psychotherapy (SFP) has been involved in the Carlow Kilkenny South Tipperary Adult Mental Services since 1994: in the main this involved meeting with service users, their families, couples and friends. However, from 2012 to 2019 five SFPs retired. This occurred when decisions were made by some Mental Health Management not to replace those SFPs that retired: thereby reducing the number of SFPs in the Southeast Adult Mental Health Services (AMHS); presumably due to funding difficulties at that time. However, as the months and years went by it became oblivious that two AMHSs were not going to employ SPTs. It was obvious that the AMHS in Waterford had never employed any SFT, and Wexford AMHS has only employed a half-time SFT for four Community Mental Teams. Consequently, this had an impact on the availability of SFPs in AMHSs in the south east AMHSs. However, on the other hand, the Carlow Kilkenny AMHS continues to be supported from Management and colleagues; SFTs since 1997. This is obvious as all Community Mental Health Teams refer service users attends the AMHSs in Carlow and Kilkenny, as well as their families/partners/friends for SFP. This article will try to ascertain how this came about, and what can be done to influences AMHS managers’ and concerning supporting SFPs.
Key words: Family Therapy; Families; Mental Health Services; Family Meetings; Context in family therapy
Structural and magnetic properties of co-sputtered Fe0.8C0.2 thin films
We studied the structural and magnetic properties of \FeC~thin films
deposited by co-sputtering of Fe and C targets in a direct current magnetron
sputtering (dcMS) process at a substrate temperature (\Ts) of 300, 523 and
773\,K. The structure and morphology was measured using x-ray diffraction
(XRD), x-ray absorption near edge spectroscopy (XANES) at Fe and C
-edges and atomic/magnetic force microscopy (AFM, MFM), respectively. An
ultrathin (3\,nm) \FeC~layer, placed between relatively thick
\FeC~layers was used to estimate Fe self-diffusion taking place during growth
at different \Ts~using depth profiling measurements. Such \FeC~layer was
also used for Fe conversion electron M\"{o}ssbauer spectroscopy (CEMS)
and nuclear resonance scattering (NRS) measurements, yielding the magnetic
structure of this ultrathin layer. We found from XRD measurements that the
structure formed at low \Ts~(300\,K) is analogous to Fe-based amorphous alloy
and at high \Ts~(773\,K), pre-dominantly a \tifc~phase has been formed.
Interestingly, at an intermediate \Ts~(523\,K), a clear presence of
\tefc~(along with \tifc~and Fe) can be seen from the NRS spectra. The
microstructure obtained from AFM images was found to be in agreement with XRD
results. MFM images also agrees well with NRS results as the presence of
multi-magnetic components can be clearly seen in the sample grown at \Ts~=
523\,K. The information about the hybridization between Fe and C, obtained from
Fe and C -edges XANES also supports the results obtained from other
measurements. In essence, from this work, experimental realization of \tefc~has
been demonstrated. It can be anticipated that by further fine-tuning the
deposition conditions, even single phase \tefc~phase can be realized which
hitherto remains an experimental challenge.Comment: 11 pages, 9 figure
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