arXiv subjects

Sung-Ho Suck Salk

Publications and source records attributed to Sung-Ho Suck Salk.

32 records · Page 2Linked to original sources

arXiv2000

Holon Pair Bose Condensation in High $T_c$ Cuprates; Symmetry Breaking and Supersymmetry Conditions

Using the t-J Hamiltonian of U(1) slave-boson symmetry, bose condensation is discussed by showing the occurrence of symmetry breaking in the hole doped high $T_c$ cuprates. The symmetry breaking is shown to take place with the d-wave hole pairing, but not with the s-wave hole pairing. Based on a derived supersymmetry Hamiltonian we find that there exists a possibility of supersymmetry conditions in association with the pairing order parameters of both spinon and holon.

cond-mat.supr-con↗

arXiv2000

High $T_c$ Phase Diagram based on the SU(2) Slave-Boson Approach to the t-J Hamiltonian

Based on an improved SU(2) slave-boson approach to the t-J Hamiltonian, we derive a phase diagram of high $T_c$ cuprates which displays both the superconducting and pseudogap phases in the plane of temperature vs. hole doping rate. It is shown that the inclusion of phase fluctuations in the order parameters results in a closer agreement with the observed superconducting temperature(bose condensation line) of an arch shape as a function of hole doping rate.

cond-mat.supr-con↗

arXiv1999

Phase Separation Based on U(1) Slave-boson Functional Integral Approach to the t-J Model

We investigate the phase diagram of phase separation for the hole-doped two dimensional system of antiferromagnetically correlated electrons based on the U(1) slave-boson functional integral approach to the t-J model. We show that the phase separation occurs for all values of J/t, that is, whether $0 < J/t < 1$ or $J/t \geq 1$ with J, the Heisenberg coupling constant and t, the hopping strength. This is consistent with other numerical studies of hole-doped two dimensional antiferromagnets. The phase separation in the physically interesting J region, $0 < J/t \lesssim 0.4$ is examined by introducing hole-hole (holon-holon) repulsive interaction. We find from this study that with high repulsive interaction between holes the phase separation boundary tends to remain robust in this low $J$ region, while in the high J region, J/t > 0.4, the phase separation boundary tends to disappear.

cond-mat.supr-con↗

arXiv1999

Effects of nonmagnetic impurities on optical conductivity in strongly correlated systems

Effects of nonmagnetic impurities on optical conductivity in the systems of antiferromagnetically correlated electrons are examined based on the Lanczos exact diagonalization scheme. As a result of resonant scattering a low-frequency peak in the optical conductivity is predicted to occur in the presence of the nonmagnetic impurities, which is consistent with the observed normal-state optical conductivity of ${\rm YBa_2}({\rm Cu}_{1-x}{\rm Zn}_x)_3{\rm O}_{7-δ}$. In addition, a relatively high and broad peak is found to occur at a high frequency region as a consequence of the Heisenberg interaction between electrons, in agreement with observation in the peak position.

cond-mat.str-el↗

arXiv1999

Functional Schrödinger Representations of Holstein-Primakoff Boson and Slave-Boson Theories for Heisenberg Antiferromagnets

We present functional Schrödinger representations of Holstein-Primakoff boson and slave-boson theories for the Heisenberg Hamiltonian and the $t-J$ Hamiltonian respectively. Based on these representations we obtain the dispersion relations of magnons for two dimensional antiferromagnets. By applying the functional Schrödinger representation of the Holstein-Primakoff boson theory to the Heisenberg Hamiltonian, the exchange energy is correctly predicted and the self-energy of quasi-hole is obtained. From the use of the functional Schrödinger representation of the $t-J$ Hamiltonian it is shown that at half-filling the dispersion relation obtained from the slave-boson theory leads to that obtained from the Holstein-Primakoff boson approach.

cond-mat.str-el↗

arXiv1999

Geometric (Berry) phases and statistical transmutation in the two-dimensional systems of strongly correlated electrons

Focusing on the hole-doped two-dimensional systems of strongly correlated electrons, we examine geometric phases acquired by electronic wave functions as a result of polaron transport around a closed loop. For this study we apply the Lanczos exact diagonalization method to Holstein-Hubbard, Holstein-$tJ$, and Holstein-$tJ_z$ models in order to reveal various aspects of geometric phases. We demonstrate that transverse spin fluctuations are responsible for the generation of nontrivial geometric phases. From the exchange symmetry of polarons we find that the statistical transmutation of polarons occurs depending on the strength of electron correlations.

cond-mat.str-el↗

arXiv1999

Lanczos exact diagonalization study of field-induced phase transition for Ising and Heisenberg antiferromagnets

Using an exact diagonalization treatment of Ising and Heisenberg model Hamiltonians, we study field-induced phase transition for two-dimensional antiferromagnets. For the system of Ising antiferromagnet the predicted field-induced phase transition is of first order, while for the system of Heisenberg antiferromagnet it is the second-order transition. We find from the exact diagonalization calculations that the second-order phase transition (metamagnetism) occurs through a spin-flop process as an intermediate step.

cond-mat.str-el↗

arXiv1998

Study of Holon Pair Condensation Based on the U(1) Slave Boson Approach to a Modified t-J Hamiltonian

In order to obtain a reasonable phase diagram involving hole-pair condensation for hole-doped cuprate systems, we propose a modified t-J Hamiltonian in which a Coulomb repulsion term between nearest neighbor holes is considered. We show from the investigation of free energy that holon pair condensation can occur as a result of symmetry breaking. In addition, we introduce a possibility of supersymmetry condition at $T=0K$ in the intermediate region between the antiferromagnetic phase and the superconducting phase.

cond-mat.supr-con↗

arXiv1998

Study of Harper's Equation for the 2-D Systems of Antiferromagnetically Correlated Electrons in an External Magnetic Field

Considering interacting (antiferromagnetically correlated) electrons, we derive a generalized Harper's equation for the square lattice of infinite size. We obtain an analytic expression for the density of states from the newly derived Harper's equation. We present a predicted phase diagram of staggered magnetization in the plane of temperature vs doping rate and discover a possibility of reentrant behavior of the staggered magnetization even in the presence of applied magnetic field. It is shown that below a critical electron correlation strength (Coulomb repulsion) the staggered magnetization in the presence of magnetic field vanishes at an even denominator $q$ value but not at odd $q$ of a given magnetic flux quantum per plaquette, $p/q$.

cond-mat.str-el↗

arXiv1998

Quasiparticle Energy Dispersion and Shadow Peaks in a Doped SO(5) Symmetric Ladder

Mean field and exact diagonalization studies on the quasiparticle excitation of an SO(5) symmetric two-leg ladder system are reported. It is shown that the energy gap in the quasiparticle excitation is caused by the formation of rung singlet states. We find that shadow peaks can occur above the Fermi surface with antiferromagnetic electron correlations involving only rungs in the spin ladder.

cond-mat.str-el↗

arXiv1997

Spin-Allowed Chern-Simons Theory of Fractional Quantum Hall States for Odd and Even Denominator Filling Factors

By allowing the spin degrees of freedom, we present a generalized spin allowed $U(1)\times U(1)$ Chern-Simons theory of fractional quantum Hall effects for odd and even denominator filling factors in single layers. This theory is shown to reproduce all possible odd denominator filling factors corresponding to spin-unpolarized, partially polarized, and fully polarized fractional quantum Hall states. Closely following our earlier theory, we derive the formal expressions of electromagnetic polarization tensors and Hall conductivity for the spin-unpolarized and partially polarized fractional quantum Hall states. Finally we report the computed spectra of collective excitations for both the even and odd denominator filling factors for which Kohn's theorem is satisfied.

cond-mat.mes-hall↗

arXiv1997

Effects of Electron Correlations on Hofstadter Spectrum

By allowing interactions between electrons, a new Harper's equation is derived to examine the effects of electron correlations on the Hofstadter energy spectra. It is shown that the structure of the Hofstadter butterfly ofr the system of correlated electrons is modified only in the band gaps and the band widths, but not in the characteristics of self-similarity and the Cantor set.

cond-mat↗

arXiv1996

The Fermion Chern-Simons Gauge Theory of Fractional Quantum Hall Effect for Electromagnetic Polarization Tensor

Unlike an earlier theory, by avoiding both the electromagnetic gauge field shift and the assumption of the zero average of electromagnetic field fluctuation the fermion Chern-Simons gauge theory is reformulated to obtain mean field solutions and a self-consistent expression of the electromagnetic polarization tensor in terms of the composite fermion picture for the systems of fractional quantum Hall effect. Thus the newly derived electromagnetic polarization tensor is shown to depend on the residual (effective) magnetic field `seen' by composite fermions rather than the statistical field, which differs from the earlier theory. The present theory reproduces the Hall conductance of fractional quantum Hall effect. The self-consistent picture of the composite fermion is maintained in all of our derivations: both the mean field solutions and the electromagnetic polarization tensor are described by the residual magnetic field seen by the composite fermions.

cond-mat↗

arXiv1996

Undulatory Variation of Antiferromagnetic Strength with Magnetic Field Based on Hubbard Model Hamiltonian

Using the Hubbard model Hamiltonian in a mean field level, we examine the variation of antiferromagnetic strength with applied magnetic field. It is demonstrated that minima in the antiferromagnetic strength exist at the the even integer denominator values of rational number for magnetic flux per plaquette. The undulatory behavior of antiferromagnetic strength with the external magnetic field is found. It is seen to be related to the undulatory net statistical phase owing to the influence of the applied magnetic field.

cond-mat↗