997 resultados para Quantum spin Hall insulator


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This article discusses the prospects of quantum psychiatry from a Bohmian point of view, which provides an ontological interpretation of quantum theory, and extends such ontology to include mind. At first, we discuss the more general relevance of quantum theory to psychopathology. The basic idea is that because quantum theory emphasizes the role of wholeness, it might be relevant to psychopathology, where breakdown of unity in the mental domain is a key feature. We then discuss the role of information in psychopathology, and consider the connections with quantum theory in this area. In particular, we discuss David Bohm’s notion of active information, which arises in the ontological interpretation of quantum theory, and is suggested to play a fundamental role as the bridge between mind and matter. Some such bridge is needed if we are to understand how subtle mental properties are able to influence more manifest physical properties in the brain (all the way to the molecular and possibly microtubular level), and how changes in those possibly quantum‐level physical processes are able to influence higher cognitive functions. We also consider the implications of the notion of active information for psychopathology. The prospects of implementing the Bohmian scheme in neuroquantal terms are then briefly considered. Finally, we discuss some possible therapeutic implications of Bohm’s approach to information and the relation of mind and matter.

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This article discusses the prospects of quantum psychiatry from a Bohmian point of view, which provides an ontological interpretation of quantum theory, and extends such ontology to include mind. At first, we discuss the more general relevance of quantum theory to psychopathology. The basic idea is that because quantum theory emphasizes the role of wholeness, it might be relevant to psychopathology, where breakdown of unity in the mental domain is a key feature. We then discuss the role of information in psychopathology, and consider the connections with quantum theory in this area. In particular, we discuss David Bohm’s notion of active information, which arises in the ontological interpretation of quantum theory, and is suggested to play a fundamental role as the bridge between mind and matter. Some such bridge is needed if we are to understand how subtle mental properties are able to influence more manifest physical properties in the brain (all the way to the molecular and possibly microtubular level), and how changes in those possibly quantum‐level physical processes are able to influence higher cognitive functions. We also consider the implications of the notion of active information for psychopathology. The prospects of implementing the Bohmian scheme in neuroquantal terms are then briefly considered. Finally, we discuss some possible therapeutic implications of Bohm’s approach to information and the relation of mind and matter.

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Separated local field (SLF) spectroscopy is a powerful technique to measure heteronuclear dipolar couplings. The method provides site-specific dipolar couplings for oriented samples such as membrane proteins oriented in lipid bilayers and liquid crystals. A majority of the SLF techniques utilize the well-known Polarization Inversion Spin Exchange at Magic Angle (PISEMA) pulse scheme which employs spin exchange at the magic angle under Hartmann-Hahn match. Though PISEMA provides a relatively large scaling factor for the heteronuclear dipolar coupling and a better resolution along the dipolar dimension, it has a few shortcomings. One of the major problems with PISEMA is that the sequence is very much sensitive to proton carrier offset and the measured dipolar coupling changes dramatically with the change in the carrier frequency. The study presented here focuses on modified PISEMA sequences which are relatively insensitive to proton offsets over a large range. In the proposed sequences, the proton magnetization is cycled through two quadrants while the effective field is cycled through either two or four quadrants. The modified sequences have been named as 2(n)-SEMA where n represents the number of quadrants the effective field is cycled through. Experiments carried out on a liquid crystal and a single crystal of a model peptide demonstrate the usefulness of the modified sequences. A systematic study under various offsets and Hartmann-Hahn mismatch conditions has been carried out and the performance is compared with PISEMA under similar conditions.

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The variations in certain spin-Hamiltonian parameters of the Cu++ ion in dibarium copper formate tetrahydrate with temperature have been studied. Optical absorption investigations on single crystals of the salt at room temperature and 90° K. are reported. The results are discussed in terms of a model in which vibronic mixing of certain electron levels of the Cu++ ion play an important role.

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In this paper, an attempt is made to study the influence of external light waves on the thermoelectric power under strong magnetic field (TPSM) in ultrathin films (UFs), quantum wires (QWs) and quantum dots (QDs) of optoelectronic materials whose unperturbed dispersion relation of the conduction electrons are defined by three and two band models of Kane together with parabolic energy bands on the basis of newly formulated electron dispersion laws in each case. We have plotted the TPSM as functions of film thickness, electron concentration, light intensity and wavelength for UFs, QWs and ODs of InSb, GaAs, Hg1-xCdxTe and In1-xGaxAsyP1-y respectively. It appears from the figures that for UFs, the TPSM increases with increasing thickness in quantum steps, decreases with increasing electron degeneracy exhibiting entirely different types of oscillations and changes with both light intensity and wavelength and these two latter types of plots are the direct signature of light waves on opto-TPSM. For QWs, the opto-TPSM exhibits rectangular oscillations with increasing thickness and shows enhanced spiky oscillations with electron concentration per unit length. For QDs, the opto-TPSM increases with increasing film thickness exhibiting trapezoidal variations which occurs during quantum jumps and the length and breadth of the trapezoids are totally dependent on energy band constants. Under the condition of non-degeneracy, the results of opto-TPSM gets simplified into the well-known form of classical TPSM equation which the function of three constants only and being invariant of the signature of band structure.

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The electron spin resonance in undiluted single crystals of cupric acid fluoride has been investigated at room temperature with microwaves of frequency 9625 Mc/s. The anisotropy in the g value has been measured in three orthogonal planes. The principal g values gave gshort parallel = 2.410 ± 0.010, gperpendicular = 2.090 ± 0.010. The linewidth shows anisotropy with orientation. The exchange frequency has been estimated to be approximately 0.08 cm-1.The powdered specimen shows asymmetry in the line shape.

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A density-functional approach on the hexagonal graphene lattice is developed using an exact numerical solution to the Hubbard model as the reference system. Both nearest-neighbour and up to third nearest-neighbour hoppings are considered and exchange-correlation potentials within the local density approximation are parameterized for both variants. The method is used to calculate the ground-state energy and density of graphene flakes and infinite graphene sheet. The results are found to agree with exact diagonalization for small systems, also if local impurities are present. In addition, correct ground-state spin is found in the case of large triangular and bowtie flakes out of the scope of exact diagonalization methods.

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We reformulate and extend our recently introduced quantum kinetic theory for interacting fermion and scalar fields. Our formalism is based on the coherent quasiparticle approximation (cQPA) where nonlocal coherence information is encoded in new spectral solutions at off-shell momenta. We derive explicit forms for the cQPA propagators in the homogeneous background and show that the collision integrals involving the new coherence propagators need to be resummed to all orders in gradient expansion. We perform this resummation and derive generalized momentum space Feynman rules including coherent propagators and modified vertex rules for a Yukawa interaction. As a result we are able to set up self-consistent quantum Boltzmann equations for both fermion and scalar fields. We present several examples of diagrammatic calculations and numerical applications including a simple toy model for coherent baryogenesis.

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Following the path-integral approach we show that the Schwarz-Hora effect is a one-electron quantum-mechanical phenomenon in that the de Broglie wave associated with a single electron is modulated by the oscillating electric field. The treatment brings out the crucial role played by the crystal in providing a discontinuity in the longitudinal component of the electric field. The expression derived for the resulting current density shows the appropriate oscillatory behaviour in time and distance. The possibility of there being a temporal counterpart of Aharonov-Bohm effect is briefly discussed in this context.

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Following Weisskopf, the kinematics of quantum mechanics is shown to lead to a modified charge distribution for a test electron embedded in the Fermi-Dirac vacuum with interesting consequences.

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A theory of the insulator-metal transition in transition-metal compounds is developed in terms of the collapse of the effective energy gap which is a function of the thermally excited electron-hole pairs. This dependence is shown to arise from the hole-lattice interaction. The reaction of the lattice is found to be equivalent to generating an internal positive pressure (strain). Estimates show that the observed typical behaviour of the conductivity jump and the change of volume at the transition temperature can be explained by the present theory.