arXiv subjects

Chang-De Gong

Publications and source records attributed to Chang-De Gong.

40 records · Page 3Linked to original sources

arXiv2001

Single hole motion in LaMnO$_3$

We study single hole motion in LaMnO$_3$ using the classical approximation for JT lattice distortions, a modified Lang-Firsov approximation for dynamical breathing-mode phonons, and the self-consistent Born approximation (verified by exact diagonalization) for hole-orbital-excitation scattering. We show that in the realistic parameter space for LaMnO$_3$, quantum effects of electron-phonon interaction are small. The quasiparticle bandwidth $W \simeq 2.2J$ in the purely orbital t-J model. It is strikingly broadened to be of order $t$ by strong static Jahn-Teller lattice distortions even when the polaronic band narrowing is taken into account.

cond-mat.str-el↗

arXiv2001

Superconducting condensation energy and neutron resonance in high-Tc superconductors

Based on the slave-boson theory of the two-dimensional $t-t'-J$ model, we calculate the superconducting condensation energy for optimally doped and overdoped high $T_{c}$ cuprates at finite temperatures using a renormalized random phase approximation. The contributions come from the mean-field part and the antiferromagnetic spin fluctuations. In the presence of neutron resonance peak at $(π,π)$, the latter is shown to have similar temperature and doping dependences as the difference in antiferromagnetic (AF) exchange energy between the normal and the superconducting state. This difference has been proposed to be related to the superconducting condensation energy by Scalapino and White. The total condensation energy, however, is about 1/2 smaller than the proposed AF exchange energy difference and shows a more rapid decrease as the temperature rises. The doping dependence of the condensation energy is found to be consistent with experiments. In particular, near zero temperature, our result shows a good quantitative agreement with experiments.

cond-mat.supr-con↗

arXiv2000

Hole spectral functions of LaMnO3

By use of the orbital t-J model, we calculate the photoemission spectra of LaMnO3 using the exact diagonalization technique, and interpret our numerics quite well in the orbital-polaron scenario where the scattering between holes and orbital excitations is treated within the self-consistent Born approximation. The quasiparticle bandwidth is found to be of the order of J and t in the purely Coulombic and Jahn-Teller phononic model, respectively. We suggest that angle-resolved photoemission spectroscopy experiments allow one to distinguish between the orbital-polaron scenario and the Jahn-Teller polaron scenario.

cond-mat.str-el↗

arXiv1999

Impurity effects on the spin excitation spectra in a d-wave superconductor

The effects of nonmagnetic impurity on the spin excitation spectra in a $d_{x^2-y^2}$-wave superconductor are examined, using the self-consistent $t$-matrix approximation. It is shown that the impurity self-energy acts to shift the position of the resonance peak to low frequencies and broaden the peak. While the impurity vertex correction causes a broad spectral weight in the spin gap at the impurity concentrations where no clear resonance peak is observed. The gaplike feature still remains in low frequency region upon the introduction of impurities. Incorporating these two effects, we find that the result is in qualitative agreement with experiments on YBa_{2}(Cu_{1-x}Zn_{x})_{3}O_{6+y}.

cond-mat.supr-con↗