arXiv subjects

Shiping Feng

Publications and source records attributed to Shiping Feng.

At least 145 records · Page 8Linked to original sources

arXiv2006

The magnetic nature of superconductivity in doped cuprates

Within the kinetic energy driven superconducting mechanism, the magnetic nature of cuprate superconductors is discussed. It is shown that the superconducting state is controlled by both charge carrier gap function and quasiparticle coherent weight. This quasiparticle coherent weight grows linearly with the hole doping concentration in the underdoped and optimally doped regimes, and then decreases with doping in the overdoped regime, which leads to that the maximal superconducting transition temperature occurs around the optimal doping, and then decreases in both underdoped and overdoped regimes. Within this framework, we calculate the dynamical spin structure factor of cuprate superconductors, and reproduce all main features of inelastic neutron scattering experiments, including the energy dependence of the incommensurate magnetic scattering at both low and high energies and commensurate resonance at intermediate energy.

cond-mat.supr-con↗

arXiv2005

Periodicity of the giant vortex states in mesoscopic superconducting rings

The giant vortex states of a multiply connected superconductor, with radius comparable to the penetration depth and the coherence length, are theoretically investigated based on the nonlinear Ginzburg-Landau theory, in which the induced magnetic field by the super-currents is accurately taken into account. The solutions of Ginzburg-Landau equations are found to be actually independent of the angular momentum L in a gauge invariant point of view, provided that the hole is in the center. Different cases with the paramagnetic current, the diamagnetic current, and the coexistence of the above two, have been studied numerically. The interpretation of the L-independent solutions of Ginzburg-Landau equations is given based on the same principle of Aharonov-Bohm effect, and could be observed by Little-Parks like oscillations near the phase boundary.

cond-mat.supr-con↗

arXiv2005

Enhancement of superconducting transition temperature by the additional second neighbor hopping t' in the t-J model

Within the kinetic energy driven superconducting mechanism, the effect of the additional second neighbor hopping t' on the superconducting state of the t-J model is discussed. It is shown that t' plays an important role in enhancing the superconducting transition temperature of the t-J model. It is also shown that the superconducting-state of cuprate superconductors is the conventional Bardeen-Cooper-Schrieffer like, so that the basic Bardeen-Cooper-Schrieffer formalism is still valid in quantitatively reproducing the doping dependence of the superconducting gap parameter and superconducting transition temperature, and electron spectral function at $(π,0)$ point, although the pairing mechanism is driven by the kinetic energy by exchanging dressed spin excitations.

cond-mat.supr-con↗

arXiv2005

Kinetic energy driven superconductivity in the electron doped cobaltate Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O

Within the charge-spin separation fermion-spin theory, we have shown that the mechanism of superconductivity in the electron doped cobaltate Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O is ascribed to its kinetic energy. The dressed fermions interact occurring directly through the kinetic energy by exchanging magnetic excitations. This interaction leads to a net attractive force between dressed fermions, then the electron Cooper pairs originating from the dressed fermion pairing state are due to the charge-spin recombination, and their condensation reveals the superconducting ground state. The superconducting transition temperature is identical to the dressed fermion pair transition temperature, and is suppressed to a lower temperature due to the strong magnetic frustration. The optimal superconducting transition temperature occurs in the electron doping concentration $δ\approx 0.29$, and then decreases for both underdoped and overdoped regimes, in qualitative agreement with the experimental results.

cond-mat.str-el↗

arXiv2005

Superconductivity in Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O driven by the kinetic energy

Within the charge-spin separation fermion-spin theory, the mechanism of superconductivity in Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O is studied. It is shown that dressed fermions interact occurring directly through the kinetic energy by exchanging magnetic excitations. This interaction leads to a net attractive force between dressed fermions(then the electron Cooper pairs), and their condensation reveals the superconducting ground state. The optimal superconducting transition temperature occurs in the electron doping concentration $δ\approx 0.29$, and then decreases for both underdoped and overdoped regimes, in qualitative agreement with the experimental results.

cond-mat.supr-con↗

arXiv2005

The charge asymmetry in superconductivity of hole- and electron-doped cuprates

Within the t-t'-J model, the charge asymmetry in superconductivity of hole- and electron-doped cuprates is studied based on the kinetic energy driven superconducting mechanism. It is shown that superconductivity appears over a narrow range of doping in electron-doped cuprates, and the superconducting transition temperature displays the same kind of the doping controlled behavior that is observed in the hole-doped case. However, the maximum achievable superconducting transition temperature in the optimal doping in electron-doped cuprates is much lower than that of the hole-doped case due to the electron-hole asymmetry.

cond-mat.supr-con↗

arXiv2005

Doping dependence of charge dynamics in electron-doped cuprates

Within the t-t'-J model, the doping dependence of charge dynamics in electron-doped cuprates is studied. The conductivity spectrum shows a pseudogap structure with a low-energy peak appearing at $ω\sim 0$ and an rather sharp midinfrared peak appearing around $ω\sim 0.3\mid t\mid$, and the resistivity exhibits a crossover from the high temperature metallic-like to low temperature insulating-like behavior in the relatively low doped regime, and a metallic-like behavior in the relatively high doped regime, in qualitative agreement with experiments. Our results also show that these unusual behaviors of the charge dynamics is intriguingly related to the magnetic correlation in the system.

cond-mat.str-el↗

arXiv2005

Thermal conductivity in the doped two-leg ladder antiferromagnet Sr$_{14-x}$Ca$_{x}$Cu$_{24}$O$_{41}$

Within the t-J model, the heat transport of the doped two-leg ladder material Sr$_{14-x}$Ca$_{x}$Cu$_{24}$O$_{41}$ is studied in the doped regime where superconductivity appears under pressure in low temperatures. The energy dependence of the thermal conductivity $κ_{c}(ω)$ shows a low-energy peak, while the temperature dependence of the thermal conductivity $κ_{c}(T)$ is characterized by a broad band. In particular, $κ_{c}(T)$ increases monotonously with increasing temperature at low temperatures $T<0.05J$, and is weakly temperature dependent in the temperature range $0.05J 0.1J$, in qualitative agreement with experiments. Our result also shows that although both dressed holons and spinons are responsible for the thermal conductivity, the contribution from the dressed spinons dominates the heat transport of Sr$_{14-x}$Ca$_{x}$Cu$_{24}$O$_{41}$.

cond-mat.str-el↗

arXiv2004

Interplay between single particle coherence and kinetic energy driven superconductivity in doped cuprates

Within the kinetic energy driven superconducting mechanism, the interplay between the single particle coherence and superconducting instability in doped cuprates is studied. The superconducting transition temperature increases with increasing doping in the underdoped regime, and reaches a maximum in the optimal doping, then decreases in the overdoped regime, however, the values of this superconducting transition temperature in the whole superconducting range are suppressed to low temperature due to the single particle coherence. Within this superconducting mechanism, we calculate the dynamical spin structure factor of cuprate superconductors, and reproduce all main features of inelastic neutron scattering experiments in the superconducting-state.

cond-mat.supr-con↗

arXiv2004

Unusual heat transport in underdoped cuprates

Within the t-J model, the heat transport of the underdoped cuprates is studied based on the fermion-spin theory. It is shown that at low temperatures the energy dependence of the thermal conductivity spectrum consists of two bands. The higher-energy band shows a weak peak, while the low-energy peak is located at a finite energy. This high-energy broad band is severely suppressed with increasing temperatures, and vanishes at higher temperature. It is also shown that the temperature dependence of the thermal conductivity increases monotonously with increasing temperatures, in agreement with experiments.

cond-mat.str-el↗

arXiv2004

Charge transport of electron doped Mott insulators on a triangular lattice

The charge transport of electron doped Mott insulators on a triangular lattice is investigated within the t-J model based on the partial charge-spin separation fermion-spin theory. The conductivity spectrum shows a low-energy peak and the unusual midinfrared band, while the resistivity is characterized by a crossover from the high temperature metallic-like to the low temperature insulating-like behavior, in qualitative agreement with experiments. Our results also show that the mechanism that cause this unusual charge transport is closely related with a competition between the kinetic energy and magnetic energy in the system.

cond-mat.str-el↗

arXiv2004

A gauge invariant dressed holon and spinon description of the normal-state of underdoped cuprates

A partial charge-spin separation fermion-spin theory is developed to study the normal-state properties of the underdoped cuprates. In this approach, the physical electron is decoupled as a gauge invariant dressed holon and spinon, with the dressed holon behaving like a spinful fermion, and represents the charge degree of freedom together with the phase part of the spin degree of freedom, while the dressed spinon is a hard-core boson, and representing the amplitude part of the spin degree of freedom. The electron local constraint for single occupancy is satisfied. Within this approach, the charge and spin dynamics of the underdoped cuprates are studied based on the t-t'-J model. It is shown that the charge dynamics is mainly governed by the scattering from the dressed holons due to the dressed spinon fluctuation, while the scattering from the dressed spinons due to the dressed holon fluctuation dominates the spin dynamics.

cond-mat.str-el↗

arXiv2003

Spin Dynamics for the t-J Model

The spin dynamics at the finite temperature for the t-J model in the underdoped and optimal doped regimes is studied within the fermion-spin theory. It is shown that the dynamical spin structure factor spectrum at the antiferromagnetic wave vector $Q=(π,π)$ are separated as low- and high-frequency parts, respectively, but the high-frequency part is suppressed in the dynamical susceptibility spectrum $χ^{''}(Q,ω)$, while the low-frequency part is the temperature dependent, which are in qualitative agreement with the experiments and numerical simulations.

cond-mat↗

arXiv2003

Coexistence of the Electron Cooper Pair and Antiferromagnetic Short-Range Correlation in Copper Oxide Materials

Within the fermion-spin theory, the physical properties of the electron pairing state in the copper oxide materials are discussed. According to the common form of the electron Cooper pair, it is shown that there is a coexistence of the electron Cooper pair and magnetic short-range correlation, and hence the antiferromagnetic short-range correlation can persist into the superconducting state. Moreover, the mean-field results indicate that the electron pairing state originating from the pure magnetic interaction in the two-dimensional t-J model is the local state, and then does not reveal the true superconducting ground-state.

cond-mat.str-el↗

arXiv2003

Universal Spin Response in Copper Oxide Materials

The spin response in the copper oxide materials at finite temperatures in the underdoped and optimal doped regimes is studied within the framework of the fermion-spin theory. The integrated dynamical spin structure factor is almost temperature independent, the integrated susceptibility shows the particularly universal behavior as $I(ω, T) \propto arctan [ a_{1}ω/T + a_{3}(ω/T)^{3}]$, and the spin-lattice relaxation time is weakly temperature dependent, which are consistent with experiments and numerical simulations.

cond-mat↗

arXiv2003

Anomalous c-axis charge dynamics in copper oxide materials

Within the t-J model, the c-axis charge dynamics of the copper oxide materials in the underdoped and optimally doped regimes is studied by considering the incoherent interlayer hopping. It is shown that the c-axis charge dynamics is mainly governed by the scattering from the in-plane fluctuation. In the optimally doped regime, the c-axis resistivity is a linear in temperatures, and shows the metallic-like behavior for all temperatures, while the c-axis resistivity in the underdoped regime is characterized by a crossover from the high temperature metallic-like behavior to the low temperature semiconducting-like behavior, which are consistent with experiments and numerical simulations.

cond-mat.str-el↗

arXiv2003

Kinetic energy driven superconductivity in doped cuprates

Within the t-J model, the mechanism of superconductivity in doped cuprates is studied based on the partial charge-spin separation fermion-spin theory. It is shown that dressed holons interact occurring directly through the kinetic energy by exchanging dressed spinon excitations, leading to a net attractive force between dressed holons, then the electron Cooper pairs originating from the dressed holon pairing state are due to the charge-spin recombination, and their condensation reveals the superconducting ground-state. The electron superconducting transition temperature is determined by the dressed holon pair transition temperature, and is proportional to the concentration of doped holes in the underdoped regime. With the common form of the electron Cooper pair, we also show that there is a coexistence of the electron Cooper pair and antiferromagnetic short-range correlation, and hence the antiferromagnetic short-range fluctuation can persist into the superconducting state. Our results are qualitatively consistent with experiments.

cond-mat.supr-con↗

arXiv2003

Unusual charge transport and spin response of doped bilayer triangular antiferromagnets

Within the t-J model, the charge transport and spin response of the doped bilayer triangular antiferromagnet are studied by considering the bilayer interaction. Although the bilayer interaction leads to the band splitting in the electronic structure, the qualitative behaviors of the physical properties are the same as in the single layer case. The conductivity spectrum shows the low-energy peak and unusual midinfrared band, the temperature dependent resistivity is characterized by the nonlinearity metallic-like behavior in the higher temperature range, and the deviation from the metallic-like behavior in the lower temperature range, and the commensurate neutron scattering peak near the half-filling is split into six incommensurate peaks in the underdoped regime, with the incommensurability increases with the hole concentration at lower dopings, and saturates at higher dopings.

cond-mat.str-el↗