arXiv subjects

Ying Liang

Publications and source records attributed to Ying Liang.

69 records · Page 4Linked to original sources

arXiv2013

Numerical study of magnetic and pairing correlation in bilayer triangular lattice

By using the determinant Quantum Monte Carlo method, the magnetic and pairing correlation of the Na$_{x}$CoO$_{2}\cdot$yH$_{2}$O system are studied within the Hubbard model on a bilayer triangular lattice. The temperature dependence of spin correlation function and pairing susceptibility with several kinds of symmetries at different electron fillings and inter layer coupling terms are investigated. It is found that the system shows an antiferromagnetic correlation around the half filling, and the $fn$-wave pairing correlation dominates over other kinds of pairing symmetry in the low doping region. As the electron filling decreases away from the half filling, both the ferromagnetic correlation and the $f$-wave paring susceptibility are enhanced and tend to dominate. It is also shown that both the magnetic susceptibility and paring susceptibility decrease as the inter layer coupling increases.

cond-mat.str-el↗

arXiv2013

Topological Superconductors in Correlated Chern Insulators

In this paper, we realize a topological superconductor (TSC) in correlated topological insulator - the interacting spinful Haldane model. We consider the electrons on the Haldane model with on-site negative-U interaction and then study its properties by mean field theory and random-phase-approximation (RPA) approach. We found that in the intermediate interaction region, the ground state becomes a TSC with the Chern number 2. We also study its edge states and the zero modes of the pi-flux.

cond-mat.supr-con↗

arXiv2012

Dynamical spin response of electron doped Mott insulators on a triangular lattice

The spin dynamics of electron doped Mott insulators on a triangular lattice is studied based on the $t-J$ model. It is found that the particularly universal behaviors of integrated dynamical spin structure factor seen in the doped Mott insulators on a square lattice, are absent in the doped Mott insulators on a triangular lattice, indicating the presence of the normal state gap. As a result, the spin-lattice relaxation rate 1/$T_{1}$ divided by $T$ reduces with decreasing temperatures in the temperature region above 0.2$J$$\approx$50K, then follows a Curie-Weiss-like behavior at the temperature less than 50K, in qualitative agreement with experimental observations.

cond-mat.str-el↗

arXiv2012

Superconductivity and magnetic fluctuations in electron-doped cobaltate superconductors

We study the interplay between superconductivity and antiferromagnetic spin fluctuations in electron-doped cobaltate Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O based on the kinetic energy driven superconductivity mechanism. We show that the superconducting state is governed by both charge carrier pairing and quasiparticle coherent, and displays a common dome-shaped phase diagram in agreement with experimental results. By calculating the dynamical spin structure factor, we theoretically find that the magnetic excitation shows a commensurate resonance peak, which locates at antiferromagnetic wave vector $Q (\frac{2π}{3},\frac{2π}{\sqrt{3}})$ for a broad range of low energies, then evolves outward into six incommensurate magnetic scattering peaks with increasing energy. Such commensurate-incommensurate spin resonance excitation should be measured by the inelastic neutron scattering technique (INS). Our present results strongly suggest that magnetic resonance can indeed be one of the fundamental features in doped Mott insulators.

cond-mat.str-el↗

arXiv2012

Particle-Hole Symmetry Protected Zero Modes on Vacancies in the Topological Insulators and Topological Superconductors on the Honeycomb Lattice

In this paper we study the quantum properties of the lattice vacancy in topological band insulators (TBIs) and topological superconductors (TSCs) on honeycomb lattice with particle-hole symmetry. Each vacancy has one zero mode for the Haldane model and two zero modes for the Kane-Mele model. In addition, in TSCs on honeycomb lattice with particle-hole symmetry, we found the existence of the Majorana zero modes around the vacancies. These zero energy modes are protected by particle-hole symmetry of these topological sates.

cond-mat.mes-hall↗

arXiv2012

Composite Spin Liquid in Correlated Topological Insulator - Spin Liquid without Spin-Charge Separation

In this paper, we found a new type of insulator - composite spin liquid which can be regarded as a short range B-type topological spin-density-wave. Composite spin liquid is topological ordered state beyond the classification of traditional spin liquid states. The elementary excitations are the "composite electrons" with both spin degree of freedom and charge degree of freedom, together with topological spin texture. This topological state supports chiral edge mode but no topological degeneracy.

cond-mat.str-el↗

arXiv2011

Topological Spin Density Wave

In this paper, we investigate the topological Hubbard model on honeycomb lattice. By considering the topological properties of the magnetic state, new types of quantum states - A-type and B-type topological spin-density-waves (A-TSDW and B-TSDW) are explored. The low energy physics is solely determined by its Chern-Simons-Hopf gauge field theories with different K-matrices. In the formulism of topological field theory, we found spin-charge separated charge-flux binding effect for A-TSDW and spin-charge synchronized charge-flux binding effect for B-TSDW. In addition, we studied the edge states and quantized Hall effect in different TSDWs.

cond-mat.str-el↗

arXiv2010

Chiral Spin Liquid in Correlated Topological Insulator

In this paper, we investigate the topological Hubbard model - the spinful Haldane model with on-site interaction on honeycomb lattice with spin rotation symmetry by using slave-rotor approach and find that chiral spin liquid exists in such a correlated electron system of the intermediate coupling region. By considering the anyon nature of excitations, chiral spin liquid may be the ground state of the topological Hubbard model. The low energy physics is basically determined by its Chern-Simons gauge theory.

cond-mat.str-el↗

arXiv2008

Density of state and non-magnetic impurity effects in electron-doped cuprates

We analyze the density of state (DOS) and a non-magnetic impurity effect in electron-doped cuprates starting from two different scenarios: the $d_{x^{2}-y^{2}}$-wave superconductivity coexisting with antiferromagnetic spin density wave (SDW) order versus $d_{x^{2}-y^{2}}$-wave superconductivity with a higher harmonic. We find that in both cases the local density of state (LDOS) exhibits two impurity-induced resonance states at low energies. We also find that for the intermediate value of the SDW gap, the DOS looks similar to that obtained from the scenario of the $d_{x^{2}-y^{2}}$-wave gap with a higher harmonic, suggesting the presence of a non-monotonic $d_{x^{2}-y^{2}}$-wave gap. However, if the SDW gap is sufficiently large the DOS looks more conventional s-wave like. This obvious difference from the DOS resulted from the $d_{x^{2}-y^{2}}$-wave gap with a higher harmonic model, could differentiate the two above scenarios and is needed to be proved in the further doping dependence of tunneling spectrum measurement.

cond-mat.str-el↗

arXiv2006

Heat transport of electron-doped Cobaltates

Within the t-J model, the heat transport of electron-doped cobaltates is studied based on the fermion-spin theory. It is shown that the temperature dependent thermal conductivity is characterized by the low temperature peak located at a finite temperature. The thermal conductivity increases monotonously with increasing temperature at low temperatures T $<$ 0.1$J$, and then decreases with increasing temperature for higher temperatures T $>$ 0.1$J$, in qualitative agreement with experimental result observed from Na$_{x}$CoO$_{2}$ .

cond-mat.str-el↗

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↗

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↗

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↗

arXiv2003

Indications of incommensurate spin fluctuations in doped triangular antiferromagnets

The incommensurate spin fluctuation of the doped triangular antiferromagnet is studied within the t-J model. It is shown that the commensurate peak near the half-filling is split into six incommensurate peaks in the underdoped and optimally doped regimes. The incommensurability increases with the hole concentration at lower dopings, and saturates at higher dopings. Although the incommensurability is almost energy independent, the weight of these incommensurate peaks decreases with energy and temperature.

cond-mat.str-el↗