The Experts below are selected from a list of 129 Experts worldwide ranked by ideXlab platform
P. Villanueva-pérez - One of the best experts on this subject based on the ideXlab platform.
-
Time reversal violation from the entangled B ^ 0 $ \overline B $ ^ 0
Journal of High Energy Physics, 2012Co-Authors: J. Bernabéu, F. Martínez-vidal, P. Villanueva-pérezAbstract:We discuss the concepts and methodology to implement an experiment probing directly Time Reversal ( T ) non-invariance, without any experimental connection to CP violation, by the exchange of in and out states. The idea relies on the B ^0 $ \overline B $ ^0 entanglement and decay time information available at B factories. The flavor or CP tag of the state of the still living neutral meson by the first decay of its orthogonal partner overcomes the problem of irreversibility for unstable systems, which prevents direct tests of T with Incoherent Particle states. T violation in the time evolution between the two decays means experimentally a difference between the rates for the time-ordered (ℓ^+ X , J/ ψ K _S ) and ( J/ ψ K _L, ℓ^− X ) decays, and three other independent asymmetries. The proposed strategy has been applied to simulated data samples of similar size and features to those currently available, from which we estimate the significance of the expected discovery to reach many standard deviations.
-
Time Reversal Violation from the entangled B0-antiB0 system
Journal of High Energy Physics, 2012Co-Authors: J. Bernabéu, F. Martínez-vidal, P. Villanueva-pérezAbstract:We discuss the concepts and methodology to implement an experiment probing directly Time Reversal (T) non-invariance, without any experimental connection to CP violation, by the exchange of "in" and "out" states. The idea relies on the B0-antiB0 entanglement and decay time information available at B factories. The flavor or CP tag of the state of the still living neutral meson by the first decay of its orthogonal partner overcomes the problem of irreversibility for unstable systems, which prevents direct tests of T with Incoherent Particle states. T violation in the time evolution between the two decays means experimentally a difference between the intensities for the time-ordered (l^+ X, J/psi K_S) and (J/psi K_L, l^- X) decays, and three other independent asymmetries. The proposed strategy has been applied to simulated data samples of similar size and features to those currently available, from which we estimate the significance of the expected discovery to reach many standard deviations.
M Minola - One of the best experts on this subject based on the ideXlab platform.
-
crossover from collective to Incoherent spin excitations in superconducting cuprates probed by detuned resonant inelastic x ray scattering
Physical Review Letters, 2017Co-Authors: M Minola, G Dellea, H Gretarsson, Yingying Peng, Y Lu, M W Haverkort, Ying Ding, Xingjiang Zhou, Darren C Peets, L ChauviereAbstract:: Spin excitations in the overdoped high temperature superconductors Tl_{2}Ba_{2}CuO_{6+δ} and (Bi,Pb)_{2}(Sr,La)_{2}CuO_{6+δ} were investigated by resonant inelastic x-ray scattering (RIXS) as functions of doping and detuning of the incoming photon energy above the Cu-L_{3} absorption peak. The RIXS spectra at optimal doping are dominated by a paramagnon feature with peak energy independent of photon energy, similar to prior results on underdoped cuprates. Beyond optimal doping, the RIXS data indicate a sharp crossover to a regime with a strong contribution from Incoherent Particle-hole excitations whose maximum shows a fluorescencelike shift upon detuning. The spectra of both compound families are closely similar, and their salient features are reproduced by exact-diagonalization calculations of the single-band Hubbard model on a finite cluster. The results are discussed in the light of recent transport experiments indicating a quantum phase transition near optimal doping.
-
collective nature of spin excitations in superconducting cuprates probed by resonant inelastic x ray scattering
Physical Review Letters, 2015Co-Authors: M Minola, G Dellea, H Gretarsson, Yingying Peng, Y Lu, J Porras, T Loew, F Yakhou, N B Brookes, Yaobo HuangAbstract:We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+x}$ over a wide range of doping levels ($0.1\ensuremath{\le}x\ensuremath{\le}1$). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all $x$. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from Incoherent Particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.
-
collective nature of spin excitations in superconducting cuprates probed by resonant inelastic x ray scattering
arXiv: Superconductivity, 2015Co-Authors: M Minola, G Dellea, H Gretarsson, Yingying Peng, Y Lu, J Porras, T Loew, F Yakhou, N B Brookes, Yaobo HuangAbstract:We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa2Cu3O6+x over a wide range of doping levels (0.1 < x < 1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from Incoherent Particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002(2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.
Martin Panholzer - One of the best experts on this subject based on the ideXlab platform.
-
Observation of a roton collective mode in a two-dimensional Fermi liquid
Nature, 2012Co-Authors: Henri Godfrin, Matthias Meschke, Hans-jochen Lauter, Ahmad Sultan, Helga M. Böhm, Eckhard Krotscheck, Martin PanholzerAbstract:Understanding the dynamics of correlated many-body quantum systems is a challenge for modern physics. Owing to the simplicity of their Hamiltonians, ^4He (bosons) and ^3He (fermions) have served as model systems for strongly interacting quantum fluids, with substantial efforts devoted to their understanding. An important milestone was the direct observation of the collective phonon–roton mode in liquid ^4He by neutron scattering, verifying Landau’s prediction^ 1 and his fruitful concept of elementary excitations. In a Fermi system, collective density fluctuations (known as ‘zero-sound’ in ^3He, and ‘plasmons’ in charged systems) and Incoherent Particle–hole excitations are observed. At small wavevectors and energies, both types of excitation are described by Landau’s theory of Fermi liquids^ 2 , 3 . At higher wavevectors, the collective mode enters the Particle–hole band, where it is strongly damped. The dynamics of Fermi liquids at high wavevectors was thus believed to be essentially Incoherent. Here we report inelastic neutron scattering measurements of a monolayer of liquid ^3He, observing a roton-like excitation. We find that the collective density mode reappears as a well defined excitation at momentum transfers larger than twice the Fermi momentum. We thus observe unexpected collective behaviour of a Fermi many-body system in the regime beyond the scope of Landau’s theory. A satisfactory interpretation of the measured spectra is obtained using a dynamic many-body theory^ 4 . Collective modes, such as phonons (lattice vibrations) and plasmons (plasma oscillations) are fundamental concepts for the description of interacting Particles. In a Fermi system such as ^3He, collective density fluctuations (known as zero-sound) and Incoherent Particle–hole excitations are observed. At small energies, both types of excitations are described by Landau's theory of Fermi liquids. At higher energies, the collective mode disappears, resulting in essentially Incoherent dynamics. The authors report measurements of a monolayer of liquid ^3He that contradict this picture, showing that a collective excitation does exist at high energies. They explain this unexpected behaviour with a theory that extends the scope of the original Landau framework. Neutron scattering measurements of a monolayer of liquid ^3He reveal an unexpected collective excitation at high wavevectors, which is described well by a dynamic many-body theory of Fermi liquids.
-
Roton collective mode observed in a two-dimensional Fermi liquid
Nature, 2012Co-Authors: Henri Godfrin, Matthias Meschke, Hans-jochen Lauter, Ahmad Sultan, Helga M. Böhm, Eckhard Krotscheck, Martin PanholzerAbstract:Understanding the dynamics of correlated many-body quantum systems has been a challenge for modern physics. Due to the simplicity of their Hamiltonian, 4He (bosons) and 3He (fermions) have served as paradigm for strongly interacting quantum fluids. For this reason, substantial efforts have been devoted to their understanding. An important milestone was the direct observation of the collective "phonon-roton" mode in liquid 4He by neutron scattering, verifying Landau's prediction and his fruitful concept of elementary excitations. In a Fermi system, collective density fluctuations ("zero-sound" in 3He, "plasmons" in charged systems) as well as Incoherent Particle-hole (PH) excitations are observed. At small wave-vectors and energies, both types of excitations are described by Landau's theory of Fermi liquids. At higher wavevectors, the collective mode enters the PH band, where it is strongly damped. The dynamics of Fermi liquids at high wave-vectors was thus believed to be essentially Incoherent. We report here the first observation of a roton-like excitation in a Fermi liquid, obtained in a monolayer of liquid 3He, studied by inelastic neutron scattering. We find that the collective density mode reappears as a well-defined excitation at momentum transfers larger than twice the Fermi momentum. We thus observe unexpected collective behaviour of a Fermi many-body system in the region outside the scope of Landau's theory. A satisfactory interpretation of the measured spectra is obtained within a novel dynamic many-body theory.
Bohdan Mariański - One of the best experts on this subject based on the ideXlab platform.
-
Multistep proton scattering—towards higher energies
Nuclear Physics, 2002Co-Authors: P. Demetriou, A. Marcinkowski, Bohdan MariańskiAbstract:Abstract The multistep direct theory of Feshbach, Kerman and Koonin is applied to the analysis of nucleon inelastic scattering to the continuum. The one-step cross sections include contributions of Incoherent Particle-hole and collective excitations in the continuum. The multistep formalism is used with the non-DWBA matrix elements that involve the biorthogonally conjugated distorted waves. The multistep direct cross sections are combined with multistep compound and compound nucleus cross sections to give a complete analysis of proton inelastic scattering by iron at energies 29 MeV, 39 MeV and 62 MeV. The results show large contributions from the two-, three- and four-step reactions. A good agreement with experiment is obtained at all energies.
-
Cross Sections for Multistep Direct Reactions
Journal of Nuclear Science and Technology, 2002Co-Authors: Paraskevi Demetriou, Andrzej Marcikowski, Bohdan MariańskiAbstract:Inelastic scattering and charge-exchange reactions have been analysed at energies ranging from 14 to 27 MeV using the modified multistep direct reaction theory (MSD) of Feshbach, Kerman and Koonin.1) The modified theory considers the non-DWBA matrix elements in the MSD cross section formulae and includes both Incoherent Particle- hole excitations and coherent collective excitations in the continuum, according to the prescription of. 2,3) The results show important contributions from multistep processes at all energies considered.
Yaobo Huang - One of the best experts on this subject based on the ideXlab platform.
-
collective nature of spin excitations in superconducting cuprates probed by resonant inelastic x ray scattering
Physical Review Letters, 2015Co-Authors: M Minola, G Dellea, H Gretarsson, Yingying Peng, Y Lu, J Porras, T Loew, F Yakhou, N B Brookes, Yaobo HuangAbstract:We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6+x}$ over a wide range of doping levels ($0.1\ensuremath{\le}x\ensuremath{\le}1$). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all $x$. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from Incoherent Particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002 (2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.
-
collective nature of spin excitations in superconducting cuprates probed by resonant inelastic x ray scattering
arXiv: Superconductivity, 2015Co-Authors: M Minola, G Dellea, H Gretarsson, Yingying Peng, Y Lu, J Porras, T Loew, F Yakhou, N B Brookes, Yaobo HuangAbstract:We used resonant inelastic x-ray scattering (RIXS) with and without analysis of the scattered photon polarization, to study dispersive spin excitations in the high temperature superconductor YBa2Cu3O6+x over a wide range of doping levels (0.1 < x < 1). The excitation profiles were carefully monitored as the incident photon energy was detuned from the resonant condition, and the spin excitation energy was found to be independent of detuning for all x. These findings demonstrate that the largest fraction of the spin-flip RIXS profiles in doped cuprates arises from magnetic collective modes, rather than from Incoherent Particle-hole excitations as recently suggested theoretically [Benjamin et al. Phys. Rev. Lett. 112, 247002(2014)]. Implications for the theoretical description of the electron system in the cuprates are discussed.
