Loading

Error: Cannot Load Popup Box

Hit List

Title:

Fluctuating charge density waves in the Hubbard model

Author:

Description:

The charge susceptibility of the two-dimensional repulsive Hubbard model is investigated using the diagram technique developed for the case of strong correlations. In this technique, a power series in the hopping constant is used. It is shown that once the Fermi level crosses one of the Hubbard subbands a sharp peak appears in the momentum depen...

The charge susceptibility of the two-dimensional repulsive Hubbard model is investigated using the diagram technique developed for the case of strong correlations. In this technique, a power series in the hopping constant is used. It is shown that once the Fermi level crosses one of the Hubbard subbands a sharp peak appears in the momentum dependence of the static susceptibility. With further departure from half-filling the peak transforms to a ridge around the $\Gamma$ point. In the considered range $0\leq|1-\bar{n}|\alt 0.2$ of the electron filling $\bar{n}$ the static susceptibility is finite which points to the absence of the long-range charge ordering. However, for $|1-\bar{n}|\approx 0.12$ the susceptibility maxima are located halfway between the center and the boundaries of the Brillouin zone. In this case an interaction of carriers with tetragonal distortions can stabilize the charge density wave with the wavelength of four lattice spacings, as observed experimentally in the low-temperature tetragonal phase of lanthanum cuprates. In the range of parameters inherent in cuprate perovskites the character of the susceptibility evolution with $\bar{n}$ depends only weakly on the ratio of the nearest-neighbor hopping constant to the Hubbard repulsion and on details of the initial band structure. The location of the susceptibility maxima in the Brillouin zone is mainly determined by the value of $\bar{n}$. ; Comment: 8 pages, 4 figures Minimize

Year of Publication:

2007-12-28

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons

Condensed Matter - Strongly Correlated Electrons Minimize

DDC:

530 Physics *(computed)*

Content Provider:

My Lists:

My Tags:

Notes:

Title:

Low-frequency incommensurate magnetic response in strongly correlated systems

Author:

Description:

It is shown that in the t-J model of Cu-O planes at low frequencies the dynamic spin structure factor is peaked at incommensurate wave vectors (1/2+-delta,1/2)$, (1/2,1/2+-delta). The incommensurability is connected with the momentum dependencies of the magnon frequency and damping near the antiferromagnetic wave vector. The behavior of the inco...

It is shown that in the t-J model of Cu-O planes at low frequencies the dynamic spin structure factor is peaked at incommensurate wave vectors (1/2+-delta,1/2)$, (1/2,1/2+-delta). The incommensurability is connected with the momentum dependencies of the magnon frequency and damping near the antiferromagnetic wave vector. The behavior of the incommensurate peaks is similar to that observed in La_{2-x}(Ba,Sr)_xCuO_{4+y} and YBa_2Cu_3O_{7-y}: for hole concentrations 0.02<x<=0.12 we find that delta is nearly proportional to x, while for x>0.12 it tends to saturation. The incommensurability disappears with increasing temperature. Generally the incommensurate magnetic response is not accompanied by an inhomogeneity of the carrier density. ; Comment: 4 pages, 4 figures Minimize

Year of Publication:

2004-02-20

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity Minimize

Content Provider:

My Lists:

My Tags:

Notes:

Title:

Temperature behavior of the magnon modes of the square lattice antiferromagnet

Author:

Description:

A spin-wave theory of short-range order in the square lattice Heisenberg antiferromagnet is formulated. With growing temperature from T=0 a gapless mode is shown to arise simultaneously with opening a gap in the conventional spin-wave mode. The spectral intensity is redistributed from the latter mode to the former. For low temperatures the theor...

A spin-wave theory of short-range order in the square lattice Heisenberg antiferromagnet is formulated. With growing temperature from T=0 a gapless mode is shown to arise simultaneously with opening a gap in the conventional spin-wave mode. The spectral intensity is redistributed from the latter mode to the former. For low temperatures the theory reproduces results of the modified spin-wave theory by M.Takahashi, J.E.Hirsch et al. and without fitting parameters gives values of observables in good agreement with Monte Carlo results in the temperature range 0 <= T < 0.8J where J is the exchange constant. ; Comment: 12 pages, 2 figures Minimize

Year of Publication:

1999-05-24

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Statistical Mechanics

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Statistical Mechanics Minimize

Content Provider:

My Lists:

My Tags:

Notes:

Title:

Pseudogaps and magnetic properties of the two-dimensional t-J model

Author:

Description:

We apply the modified spin-wave theory with the constraint of zero staggered magnetization to investigate normal-state spectral and magnetic properties of the 2D t-J model in the paramagnetic state. A set of self-energy equations for hole and magnon Green's functions is solved numerically in the self-consistent Born approximation. The constraint...

We apply the modified spin-wave theory with the constraint of zero staggered magnetization to investigate normal-state spectral and magnetic properties of the 2D t-J model in the paramagnetic state. A set of self-energy equations for hole and magnon Green's functions is solved numerically in the self-consistent Born approximation. The constraint can be fulfilled in the ranges of hole concentrations 0.02 < x < 0.17 and temperatures T < 150 K. In this region the hole spectrum differs from a conventional metallic spectrum which is manifested in the variation with x of the quasiparticle weights of states and in the violation of Luttinger's theorem. With decreasing x from x = 0.17 hidden parts appear in the hole Fermi surface which can be interpreted as the opening of a pseudogap near (pi,0). Obtained size, symmetry and concentration dependence of the pseudogap are in agreement with photoemission data in Bi2212. Calculated temperature dependencies of the spin correlation length, spin-lattice relaxation times at the Cu and O sites, and static susceptibility are typical for the quantum disordered regime with a pseudogap in the spectrum of magnetic excitations. These quantities are in qualitative and in some cases in quantitative agreement with experiment in underdoped YBa2Cu3O(6+y). At x > 0.12 the considered phase borders the phase of conventional metal. ; Comment: 25 pages, 12 Postscript figures, uses psfig.sty Minimize

Year of Publication:

1998-08-08

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity Minimize

DDC:

530 Physics *(computed)*

Content Provider:

My Lists:

My Tags:

Notes:

Title:

Magnetic susceptibility in the pseudogap phase of cuprate perovskites

Author:

Description:

We calculate the magnetic susceptibility in the pseudogap phase of cuprates using the two-dimensional $t-J$ model and the Mori projection operator technique. In this phase, the Fermi arcs lead to a quasi-elastic incommensurate magnetic response for low temperatures. The theory accounts for the reorientation of the susceptibility maxima from the ...

We calculate the magnetic susceptibility in the pseudogap phase of cuprates using the two-dimensional $t-J$ model and the Mori projection operator technique. In this phase, the Fermi arcs lead to a quasi-elastic incommensurate magnetic response for low temperatures. The theory accounts for the reorientation of the susceptibility maxima from the axial to the diagonal direction occurring at small hole concentrations in La$_{2-x}$Sr$_x$CuO$_4$. A small cusp of the hole dispersion near the Fermi level, which is connected with the spin-polaron band, affords the growth of the maxima with decreasing frequency. As in the superconducting phase, the susceptibility maxima have an hourglass dispersion. The assumption of the phase separation into regions of superconducting and pseudogap phases in underdoped cuprates explains the lack of the superconducting gap in their susceptibility. The observed rapid change of widths of the susceptibility maxima with frequency is related to the contribution of the pseudogap phase. This contribution may also explain the strengthening of the quasi-elastic response by modest magnetic fields and by small impurity concentrations. ; Comment: 11 pages, 7 figures Minimize

Year of Publication:

2011-12-06

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons

Condensed Matter - Strongly Correlated Electrons Minimize

DDC:

530 Physics *(computed)*

Content Provider:

My Lists:

My Tags:

Notes:

Title:

Peculiarities of the spectrum of strongly correlated electrons

Author:

Description:

Hole and spin Green's functions of the two-dimensional t-J model of the Cu-O planes are calculated in an approximation which retains the rotation symmetry in the paramagnetic state and has no presumed magnetic ordering. In this approximation Green's functions are represented by continued fractions which are interrupted by decouplings with a vert...

Hole and spin Green's functions of the two-dimensional t-J model of the Cu-O planes are calculated in an approximation which retains the rotation symmetry in the paramagnetic state and has no presumed magnetic ordering. In this approximation Green's functions are represented by continued fractions which are interrupted by decouplings with a vertex correction determined from the constraint of zero site magnetization in the paramagnetic state. Obtained results are shown to be in good agreement with Monte Carlo and exact diagonalization data. The calculated spectra demonstrate a pseudogap and a band splitting which are similar to those observed in Bi-based cuprate perovskites. ; Comment: 10 pages, 5 figures, Proceedings of the NATO ARW "New Trends in Superconductivity", Yalta, Ukraine, 16-20 Sept. 2001 Minimize

Year of Publication:

2001-08-29

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity Minimize

Content Provider:

My Lists:

My Tags:

Notes:

Title:

Mechanisms of the magnetic incommensurability in p-type cuprate perovskites

Author:

Description:

We use the t-J model and Mori projection operator formalism for calculating the magnetic susceptibility of p-type cuprates in the superconducting and pseudogap phases. The lack of extended tails in the peaks of the hole spectral function was shown to provide an incommensurate low-frequency response with hole dispersions derived from photoemissio...

We use the t-J model and Mori projection operator formalism for calculating the magnetic susceptibility of p-type cuprates in the superconducting and pseudogap phases. The lack of extended tails in the peaks of the hole spectral function was shown to provide an incommensurate low-frequency response with hole dispersions derived from photoemission. The theory reproduces the hourglass dispersion of the susceptibility maxima with the upper branch reflecting the dispersion of localized spin excitations and the lower branch being due to incommensurate maxima of their damping. The intensive resonance peak appears when the hourglass waist falls below the bottom of the electron-hole continuum. In the pseudogap phase, the Fermi arcs lead to a quasi-elastic incommensurate response for low temperatures. This result explains the lack of the superconducting gap in the susceptibility of phase-separated underdoped lanthanum cuprates. It may also explain the strengthening of the quasi-elastic response by magnetic fields and impurities. The theory accounts for the magnetic stripe reorientation from the axial to diagonal direction at low hole concentrations. ; Comment: 9 pages, 5 figures, Proc. of ICSM2012, Istanbul Minimize

Year of Publication:

2012-08-20

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons

Condensed Matter - Strongly Correlated Electrons Minimize

DDC:

530 Physics *(computed)*

Content Provider:

My Lists:

My Tags:

Notes:

Title:

The rotationally invariant approximation for the two-dimensional t-J model

Author:

Description:

Using the description in terms of the Hubbard operators hole and spin Green's functions of the two-dimensional t-J model are calculated in an approximation which retains the rotation symmetry of the spin susceptibility in the paramagnetic state and has no predefined magnetic ordering. In this approximation, Green's functions are represented by c...

Using the description in terms of the Hubbard operators hole and spin Green's functions of the two-dimensional t-J model are calculated in an approximation which retains the rotation symmetry of the spin susceptibility in the paramagnetic state and has no predefined magnetic ordering. In this approximation, Green's functions are represented by continued fractions which are interrupted with the help of the decoupling corrected by the constraint of zero site magnetization in the paramagnetic state. Results obtained in this approach for an undoped 32x32 lattice (the Heisenberg model) and for one hole in a 4x4 lattice are in good agreement with Monte Carlo and exact diagonalization data, respectively. In the limit of heavy doping the hole spectrum described by the obtained formulas acquires features of the spectrum of weakly correlated excitations. ; Comment: 14 pages, 3 figures, submitted to Phys. Rev. B Minimize

Year of Publication:

2002-01-29

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity

Condensed Matter - Strongly Correlated Electrons ; Condensed Matter - Superconductivity Minimize

DDC:

530 Physics *(computed)*

Content Provider:

My Lists:

My Tags:

Notes:

Title:

One-loop approximation for the Heisenberg antiferromagnet

Author:

Description:

We use the diagram technique for spin operators to calculate Green's functions and observables of the spin-1/2 quantum Heisenberg antiferromagnet on a square lattice. The first corrections to the self-energy and interaction are taken into account in the chain diagrams. The approximation reproduces main results of Takahashi's modified spin-wave t...

We use the diagram technique for spin operators to calculate Green's functions and observables of the spin-1/2 quantum Heisenberg antiferromagnet on a square lattice. The first corrections to the self-energy and interaction are taken into account in the chain diagrams. The approximation reproduces main results of Takahashi's modified spin-wave theory [Phys. Rev. B 40, 2494 (1989)] and is applicable in a wider temperature range. The energy per spin calculated in this approximation is in good agreement with the Monte Carlo and small-cluster exact-diagonalization calculations in the range 0 <= T < 1.2J where J is the exchange constant. For the static uniform susceptibility the agreement is good for T < 0.6J and becomes somewhat worse for higher temperatures. Nevertheless the approximation is able to reproduce the maximum in the temperature dependence of the susceptibility near T = 0.9J. ; Comment: 15 pages, 6 ps figures Minimize

Year of Publication:

2000-10-19

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons

Condensed Matter - Strongly Correlated Electrons Minimize

DDC:

541 Physical chemistry *(computed)*

Content Provider:

My Lists:

My Tags:

Notes:

Title:

Magnetic incommensurability and fluctuating charge density waves in the repulsive Hubbard model

Author:

Description:

Magnetic and charge susceptibilities of the two-dimensional repulsive Hubbard model are investigated applying a strong coupling diagram technique in which the expansion in powers of the hopping constants is used. For small lattices and high temperatures results are in agreement with Monte Carlo simulations. With the departure from half-filling $...

Magnetic and charge susceptibilities of the two-dimensional repulsive Hubbard model are investigated applying a strong coupling diagram technique in which the expansion in powers of the hopping constants is used. For small lattices and high temperatures results are in agreement with Monte Carlo simulations. With the departure from half-filling $x$ the low-frequency magnetic susceptibility becomes incommensurate and the incommensurability parameter grows with $x$. The incommensurability, its dependence on frequency and on $x$ resemble experimental results in lanthanum cuprates. Also for finite $x$ sharp maxima appear in the static charge susceptibility. The maxima are finite which points to the absence of the long-range charge ordering (static stripes). However, for $x\approx 0.12$ the maxima are located near the momenta $(0,\pm\pi/2)$, $(\pm\pi/2,0)$. In this case an interaction of carriers with tetragonal distortions can stabilize stripes with the wavelength of four lattice spacings, as observed in the low-temperature tetragonal phase of cuprates. As follows from the obtained results, the magnetic incommensurability is not a consequence of the stripes. ; Comment: 4 pages, 3 figures, manuscript for proceefings of LT25 Minimize

Year of Publication:

2008-06-27

Document Type:

text

Subjects:

Condensed Matter - Strongly Correlated Electrons

Condensed Matter - Strongly Correlated Electrons Minimize

DDC:

530 Physics *(computed)*

Content Provider:

My Lists:

My Tags:

Notes:

Currently in BASE: 68,072,316 Documents of 3,307 Content Sources

http://www.base-search.net