8 research outputs found
The Origin of the Pseudogap in Underdoped HTSC
Here the Origin of the pseudogap in HTSC is attributed to the modulated
antiferromagnetic (AFM) phase, whose preliminary version has been sketched
recently by the present author [1](arXiv:0901.3896v2 (cond.-mat.sup-con)).
Starting from the t-J Hamiltonian, I show that the formal failure of the
perturbation theory leads to a transformation to the pseudogap phase. This
phase is characterized by the aggregation of the holes into rows and columns,
which in turn results in two internal fields. The first is the modulated AFM
field, whose main evidence comes from Neutron scattering experiments. The
second internal field is made up by the checkerboard charge density waves that
have been observed by Scanning Tunneling Measurements. The present paper deals
mainly with the internal field of the first type, and discusses the second type
only tentatively. Formalism is derived that yields the ground state, the
internal field, the Hamiltonian, and the propagators of the condensed phase.
Our results resolve the presumably inherent self contradictory concept of
pseudogap. It is shown that the excitation energy spectrum is gapless despite
the order parameter that is inherent to the condensed system. In addition, it
is shown qualitatively that our model predicts "Fermi surface" that is in
agreement with experiment
Principles of the Field Theory of High Temperature Superconductivity in Underdoped Copper-Oxides
Here I extend my last work about the origin of the pseudo-gaps in underdoped
cuprates (arXiv: cond-mat. 1011.3206), to include the mechanism of
superconductivity. This is done by adapting the formalism of the double
correlations in systems with nested Fermi surfaces to the semi one dimensional
system of strings of holes. It is proposed that magnetic interaction is crucial
for the establishment of the pseudogap and the high temperature
superconductivity. It is shown that superconductivity disturbs the completeness
of the strings of holes, and creates fluctuations in their shapes. This, in
turn, reduces the magnetic interaction and the pseudogap order.Comment: This paper has been withdrawn by the author. 27 page
J-PARC Neutrino Beamline Upgrade Technical Design Report
In this document, technical details of the upgrade plan of the J-PARC neutrino beamline for the extension of the T2K experiment are described. T2K has proposed to accumulate data corresponding to 2Ă1022 protons-on-target in the next decade, aiming at an initial observation of CP violation with 3Ï or higher significance in the case of maximal CP violation. Methods to increase the neutrino beam intensity, which are necessary to achieve the proposed data increase, are described
J-PARC neutrino beamline upgrade technical design report
In this document, technical details of the upgrade plan of the J-PARC neutrino beamline for the extension of the T2K experiment are described. T2K has proposed to accumulate data corresponding to protons-on-target in the next decade, aiming at an initial observation of CP violation with or higher significance in the case of maximal CP violation. Methods to increase the neutrino beam intensity, which are necessary to achieve the proposed data increase, are described
Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples
International audienceSamples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed seventeen Ryugu samples measuring 1-8 mm. CO 2 -bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryuguâs parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and Ca, Al-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed by aqueous alteration reactions at low temperature, high pH, and water/rock ratios < 1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate Ryuguâs parent body formed ~ 2 million years after the beginning of Solar System formation
Ultrafast optical spectroscopy of strongly correlated materials and high-temperature superconductors: a non-equilibrium approach
In the last two decades non-equilibrium spectroscopies have evolved from avant-garde studies to crucial tools for expanding our understanding of the physics of strongly correlated materials. The possibility of obtaining simultaneously spectroscopic and temporal information has led to insights that are complementary to (and in several cases beyond) those attainable by studying the matter at equilibrium. From this perspective, multiple phase transitions and new orders arising from competing interactions are benchmark examples where the interplay among electrons, lattice and spin dynamics can be disentangled because of the different timescales that characterize the recovery of the initial ground state. For example, the nature of the broken-symmetry phases and of the bosonic excitations that mediate the electronic interactions, eventually leading to superconductivity or other exotic states, can be revealed by observing the sub-picosecond dynamics of impulsively excited states. Furthermore, recent experimental and theoretical developments have made it possible to monitor the time-evolution of both the single-particle and collective excitations under extreme conditions, such as those arising from strong and selective photo-stimulation. These developments are opening the way for new, non-equilibrium phenomena that can eventually be induced and manipulated by short laser pulses. Here, we review the most recent achievements in the experimental and theoretical studies of the non-equilibrium electronic, optical, structural and magnetic properties of correlated materials. The focus will be mainly on the prototypical case of correlated oxides that exhibit unconventional superconductivity or other exotic phases. The discussion will also extend to other topical systems, such as iron-based and organic superconductors, (Formula presented.) and charge-transfer insulators. With this review, the dramatically growing demand for novel experimental tools and theoretical methods, models and concepts, will clearly emerge. In particular, the necessity of extending the actual experimental capabilities and the numerical and analytic tools to microscopically treat the non-equilibrium phenomena beyond the simple phenomenological approaches represents one of the most challenging new frontiers in physics