Search results for "Phonon"
showing 10 items of 466 documents
Quantum Sensors Assisted by Spontaneous Symmetry Breaking for Detecting Very Small Forces
2015
We propose a quantum-sensing scheme for measuring weak forces based on a symmetry-breaking adiabatic transition in the quantum Rabi model. We show that the system described by the Rabi Hamiltonian can serve as a sensor for extremely weak forces with sensitivity beyond the yoctonewton (yN) per sqrt (Hz) range. We propose an implementation of this sensing protocol using a single trapped ion. A major advantage of our scheme is that the force detection is performed by projective measurement of the population of the spin states at the end of the transition, instead of the far slower phonon number measurement used hitherto.
Quasi-elastic reactions: an interplay of reaction dynamics and nuclear structure
2011
Multinucleon transfer reactions have been investigated in 40Ar+208Pb with the Prisma+Clara set-up. The experimental differential cross sections of different neutron transfer channels have been obtained at three different angular settings taking into account the transmission through the spectrometer. The experimental yields of the excited states have been determined via particle-γ coincidences. In odd Ar isotopes, we reported a signif cant population of 11/2− states, reached via neutron transfer. Their structure matches a stretched conf guration of the valence neutron coupled to vibration quanta.
Phononic crystals: Harnessing the propagation of sound, elastic waves, and phonons
2016
Comptes Rendus Physique - In Press.Proof corrected by the author Available online since jeudi 3 mars 2016
Resonant Raman scattering in quantum wells in high magnetic fields: Deformation-potential interaction.
1992
A theoretical study of one-phonon resonant Raman scattering in a quantum well (QW) in high magnetic fields has been performed. The Raman profiles are calculated as a function of magnetic field, quantum-well thickness, and laser frequency. The basic theory is first developed assuming parabolic masses in the plane perpendicular to the growth direction of the QW. Selection rules for deformation-potential-allowed scattering are given and a compact analytical expression for the Raman-scattering efficiency is obtained for infinite barriers. The double-resonance conditions are derived as a function of the magnetic field or well thickness. In a second part of the work, the heavy-hole\char21{}light-…
Electric-field-induced Raman scattering in GaAs: Franz-Keldysh oscillations
1995
We have studied the influence of strong electric fields on the Raman scattering intensity from LO phonons in GaAs (100) at room temperature using laser excitation energies above the fundamental ${\mathit{E}}_{0}$ gap. Striking oscillations are found in the scattering intensity for configurations where either the deformation potential or Fr\"ohlich electron-phonon interaction contribute. The oscillations in the deformation-potential-mediated scattering intensity can be related to Franz-Keldysh oscillations derived from the ${\mathit{E}}_{0}$ gap, whereas a more complicated mechanism has to be invoked for processes where Fr\"ohlich interaction is responsible.
Surface Segregation Entropy of Protons and Oxygen Vacancies in BaZrO3
2016
The perovskite BaZrO3 has attracted considerable attention in the recent decade due to its high temperature proton conducting properties, and possible application as electrolyte in intermediate temperature fuel cells and electrolyzers. In this contribution, we performed, for the first time, first-principles calculations of the phonon contribution to the defect thermodynamics of the ZrO2 terminated (001) surface of BaZrO3. The approach allows us to determine both the segregation enthalpy and entropy of defects, which we apply to two fundamental defects in BaZrO3; fully charged oxygen vacancies (vO••) and protonic defects (OHO•). The calculations show that both defects exhibit favorable segre…
Phonon-induced polariton superlattices
2006
We show that the coherent interaction between microcavity polaritons and externally stimulated acoustic phonons forms a tunable polariton superlattice with a folded energy dispersion determined by the phonon population and wavelength. Under high phonon concentration, the strong confinement of the optical and excitonic polariton components in the phonon potential creates weakly coupled polariton wires with a virtually flat energy dispersion.
The influence of quantum fluctuations on phase transition temperature in disordered ferroelectrics
2014
We consider the disordered ferroelectric, where the impurity dipoles interact via quantum optical phonons. We show that quantum fluctuations are amplified by the effects of disorder so that they can be important up to the ferroelectric phase transition temperature. In this paper, we calculate the ferroelectric phase transition temperature as a function of impurity dipole concentration. We show that quantum effects change the character of concentrational dependence of . Namely, they cause the discontinuity in so that the critical concentration is reached abruptly. We have shown that quantum effects inhibit the ferroelectricity so that larger (than that in purely classical disordered ferroele…
Orbital dimerization inNaTiSi2O6:An orbital analogue of the spin-Peierls phase transition
2004
We measure the Raman scattering spectra of NaTiSi2O6, analyze the vibrational properties, and study the origin of the phase transition in this compound. In this quasi-one-dimensional S = 1/2 system we observe anomalous high-temperature phonon broadenings, and large changes of the phonon energies and line-widths across the phase transition temperature of 210 K. These results, combined with theoretical considerations, indicate that the phonon anomalies originate from an orbital order-disorder type of phase transition. We find that the high temperature dynamical Jahn-Teller phase of NaTiSi2O6 exhibits a spontaneous breaking of translational symmetry into a dimerized, Jahn-Teller distorted, orb…
Transition to ballistic regime for heat transport in helium II
2014
The size-dependent and flux-dependent effective thermal conductivity of narrow capillaries filled with superfluid helium is analyzed from a thermodynamic continuum perspective. The classical Landau evaluation of the effective thermal conductivity of quiescent superfluid, or the Gorter-Mellinck regime of turbulent superfluids, are extended to describe the transition to ballistic regime in narrow channels wherein the radius $R$ is comparable to (or smaller than) the phonon mean-free path $\ell$ in superfluid helium. To do so we start from an extended equation for the heat flux incorporating non-local terms, and take into consideration a heat slip flow along the walls of the tube. This leads f…