arXiv subjects

Ying Zhang

Publications and source records attributed to Ying Zhang.

601 records · Page 34Linked to original sources

arXiv2003

Temperature dependent effective mass renormalization in a Coulomb Fermi liquid

We calculate numerically the quasiparticle effective mass (m*) renormalization as a function of temperature and electron density in two- and three-dimensional electron systems with long-range Coulomb interaction. In two dimensions, the leading temperature correction is linear and positive with the slope being a universal density independent number in the high density limit. We predict an enhancement of the effective mass at low temperatures and a non-monotonic temperature dependence at higher temperatures (T/T_F ~ 0.1) with the peak shifting toward higher temperatures as density decreases. In three dimensions, we find that the effective mass temperature dependence is nonlinear and non-universal, and depends on the electron density in a complicated way. At very high densities, the leading correction is positive, while at lower densities it changes sign and the effective mass decreases monotonically from its zero temperature value with increasing temperature.

cond-mat.str-el↗

arXiv2002

Competing orders in a magnetic field: spin and charge order in the cuprate superconductors

We describe two-dimensional quantum spin fluctuations in a superconducting Abrikosov flux lattice induced by a magnetic field applied to a doped Mott insulator. Complete numerical solutions of a self-consistent large N theory provide detailed information on the phase diagram and on the spatial structure of the dynamic spin spectrum. Our results apply to phases with and without long-range spin density wave order and to the magnetic quantum critical point separating these phases. We discuss the relationship of our results to a number of recent neutron scattering measurements on the cuprate superconductors in the presence of an applied field. We compute the pinning of static charge order by the vortex cores in the `spin gap' phase where the spin order remains dynamically fluctuating, and argue that these results apply to recent scanning tunnelling microscopy (STM) measurements. We show that with a single typical set of values for the coupling constants, our model describes the field dependence of the elastic neutron scattering intensities, the absence of satellite Bragg peaks associated with the vortex lattice in existing neutron scattering observations, and the spatial extent of charge order in STM observations. We mention implications of our theory for NMR experiments. We also present a theoretical discussion of more exotic states that can be built out of the spin and charge order parameters, including spin nematics and phases with `exciton fractionalization'.

cond-mat.str-el↗

arXiv2002

Transitions to equilibrium state in classical ϕ^{4} lattice

Statistical behavior of a classical $ϕ^{4}$ Hamiltonian lattice is investigated from microscopic dynamics. The largest Lyapunov exponent and entropies are considered for manifesting chaos and equipartition behaviors of the system. It is found, for the first time, that for any large while finite system size there exist two critical couplings for the transitions to equipartitions, and the scaling behaviors of these lower and upper critical couplings vs the system size is numerically obtained.

nlin.CD↗

arXiv2001

Chaos in soliton systems and special Lax pairs for chaos systems

In this letter, taking the well known (2+1)-dimensional soliton systems, Davey-Stewartson (DS) model and the asymmetric Nizhnik-Novikov-Veselov (ANNV) model, as two special examples, we show that some types of lower dimensional chaotic behaviors may be found in higher dimensional soliton systems. Especially, we derive the famous Lorenz system and its general form from the DS equation and the ANNV equation. Some types of chaotic soliton solutions can be obtained from analytic expression of higher dimensional soliton systems and the numeric results of lower dimensional chaos systems. On the other hand, by means of the Lax pairs of some soliton systems, a \em lower \rm dimensional chaos system may have some types of \em higher \rm dimensional Lax pairs. An explicit (2+1)-dimensional Lax pair for a (1+1)-dimensional chaotic equation is given.

nlin.PS↗

arXiv2001

(1+1)-dimensional turbulence systems reduced from (2+1)-dimensional Lax integrable dispersive long wave equation

After extending the Clarkson-Kruskal's direct similarity reduction ansatz to a more general form, one may obtain various new types of reduction equations. Especially, some lower dimensional turbulence systems or chaotic systems may be obtained from the general type of similarity reductions of a higher dimensional Lax integrable model. Especially, the Kuramoto-Sivashinsky equation and an arbitrary three order quasilinear equation which includes the Korteweg de-Vries Burgers equation and the general Lorenz equation as two special cases are obtained from the reductions of the (2+1)-dimensional dispersive long wave equation system. Some types of periodic and chaotic solutions of the (2+1)-dimensional dispersive long wave equation system are also discussed.

nlin.SI↗

arXiv2001

Spin ordering quantum transitions of superconductors in a magnetic field

We argue that recent neutron scattering measurements by Lake et. al. (Science 291, 1759 (2001)) of the spin excitation spectrum of LSCO in a magnetic field can be understood in terms of proximity to a phase with co-existing superconductivity and spin density wave order. We present a general theory for such quantum transitions, and argue that their low energy spin fluctuations are controlled by a singular correction from the superflow kinetic energy, acting in the region outside the vortex cores. We propose numerous experimental tests of our theory.

cond-mat.supr-con↗

arXiv2000

Competing orders and quantum criticality in doped antiferromagnets

We use a number of large-N limits to explore the competition between ground states of square lattice doped antiferromagnets which break electromagnetic U(1), time-reversal, or square lattice space group symmetries. Among the states we find are d-, (s+id)-, and (d+id)-wave superconductors, Wigner crystals, Wigner crystals of hole pairs, orbital antiferromagnets (or staggered-flux states), and states with spin-Peierls and bond-centered charge stripe order. In the vicinity of second-order quantum phase transitions between the states, we go beyond the large-N limit by identifying the universal quantum field theories for the critical points, and computing the finite temperature, quantum-critical damping of fermion spectral functions. We identify candidate critical points for the recently observed quantum-critical behavior in photoemission experiments on BSCCO by Valla et al. (Science 285, 2110 (1999)). These involve onset of a charge density wave, or of broken time-reversal symmetry with (d+id) or (s+id) pairing, in a d-wave superconductor. It is not required (although it is allowed) that the stable state in the doped cuprates to be anything other than the d-wave superconductor--the other states need only be stable nearby in parameter space. At finite temperatures, fluctuations associated with these nearby states lead to the observed fermion damping in the vicinity of the nodal points in the Brillouin zone. The cases with broken time-reversal symmetry are appealing because the order parameter is not required to satisfy any special commensurability conditions. The observed absence of inelastic damping of quasiparticles with momenta (pi,k), (k,pi) (with 0 < k < pi) also appears very naturally for the case of a transition to (d+id) order.

cond-mat.str-el↗