arXiv subjects

Zheng-Cheng Gu

Publications and source records attributed to Zheng-Cheng Gu.

95 records · Page 6Linked to original sources

arXiv2008

Tensor-entanglement renormalization group approach to 2D quantum systems

Traditional mean-field theory is a simple generic approach for understanding various phases. But that approach only applies to symmetry breaking states with short-range entanglement. In this paper, we describe a generic approach for studying 2D quantum phases with long-range entanglement (such as topological phases). Our approach is a variational method that uses tensor product states (also known as projected entangled pair states) as trial wave functions. We use a 2D real space RG algorithm to evaluate expectation values in these wave functions. We demonstrate our algorithm by studying several simple 2D quantum spin models.

cond-mat.str-el↗

arXiv2007

Charge dynamics in the phase string model for high-Tc superconductors

An understanding of the anomalous charge dynamics in the high-Tc cuprates is obtained based on a model study of doped Mott insulators. The high-temperature optical conductivity is found to generally have a two-component structure: a Drude like part followed by a mid-infrared band. The scattering rate associated with the Drude part exhibits a linear-temperature dependence over a wide range of high temperature, while the Drude term gets progressively suppressed below a characteristic energy of magnetic origin as the system enters the pseudogap phase. The high-energy optical conductivity shows a resonancelike feature in an underdoped case and continuously evolves into a 1/ωtail at higher doping, indicating that they share the same physical origin. In particular, such a high-energy component is closely correlated with the ω-peak structure of the density-density correlation function at different momenta, in systematic consistency with exact diagonalization results based on the t-J model. The underlying physics is attributed to the high-energy spin-charge separation in the model, in which the "mode coupling" responsible for the anomalous charge properties is not between the electrons and some collective mode but rather between new charge carriers, holons, and a novel topological gauge field controlled by spin dynamics, as the consequence of the strong short-range electron-electron Coulomb repulsion in the doped Mott insulator.

cond-mat.str-el↗

arXiv2006

A lattice bosonic model as a quantum theory of gravity

A local quantum bosonic model on a lattice is constructed whose low energy excitations are gravitons described by linearized Einstein action. Thus the bosonic model is a quantum theory of gravity, at least at the linear level. We find that the compactification and the discretization of metric tenor are crucial in obtaining a quantum theory of gravity.

gr-qc↗

arXiv2006

Fermion pairing with population imbalance: energy landscape and phase separation in a constrained Hilbert subspace

In this Letter we map out the mean field energy potential landscape of fermion pairing states with population imbalance near broad Feshbach Resonances. We apply the landscape to investigate the nature of phase separation, when the Hilbert space is subject to the constraint of constant population imbalance. We calculate the scattering length dependence of the critical population imbalance for various phase separated states across Feshbach resonances.

cond-mat.other↗

arXiv2005

Upper Pseudogap Phase: Magnetic Characterizations

It is proposed that the upper pseudogap phase (UPP) observed in the high-Tc cuprates correspond to the formation of spin singlet pairing under the bosonic resonating-valence-bond (RVB) description. We present a series of evidence in support of such a scenario based on the calculated magnetic properties including uniform spin susceptibility, spin-lattice and spin-echo relaxation rates, which consistently show that strong spin correlations start to develop upon entering the UPP, being enhanced around the momentum (π, π) while suppressed around (0, 0). The phase diagram in the parameter space of doping concentration, temperature, and external magnetic field, is obtained based on the the bosonic RVB theory. In particular, the competition between the Zeeman splitting and singlet pairing determines a simple relation between the "critical" magnetic field, H_{PG}, and characteristic temperature scale, T0, of the UPP. We also discuss the magnetic behavior in the lower pseudogap phase at a temperature Tv lower than T0, which is characterized by the formation of Cooper pair amplitude where the low-lying spin fluctuations get suppressed at both (0, 0) and (π, π). Properties of the UPP involving charge channels will be also briefly discussed.

cond-mat.str-el↗