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Search Results: 1 - 10 of 128249 matches for " Fu-Chun Zhang "
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Momentum-Resolved Electronic Relaxation Dynamics in D-wave Superconductors
Yong Wang,Fu-Chun Zhang
Physics , 2013, DOI: 10.1103/PhysRevB.89.094519
Abstract: Motivated by recent development in time-resolved angle-resolved photoemission spectroscopy (trARPES) for d-wave superconductors, we analyze the non-equilibrium relaxation dynamics of the laser pulse excited sample within the scenario of two-temperature model. It is shown that the main features reported in the trARPES technique may be understood within this phenomenological picture. The momentum dependence of the excited quasiparticle density and the relaxation rate is associated with the dynamics of the nodal d-wave superconducting gap, and the fluence dependence of the relaxation rate is related to the recombination process of quasiparticles into Cooper pairs.
On the origin of biquadratic exchange in spin 1 chains
Frederic Mila,Fu-Chun Zhang
Physics , 2000, DOI: 10.1007/s100510070242
Abstract: One dimensional spin 1 systems may have a rich phase diagram including Haldane gap and dimerized phases if the usually very small biquadratic exchange becomes significant. We show that this unlikely condition may be fulfilled in electron systems with quasi-degenerate orbitals. This mechanism may have been experimentally realized in the spin 1 chain LiVGe$_2$O$_6$. The implications for the exploration of the physics and quantum chemistry of spin 1 chains are discussed.
An Anyon Superconducting Groundstate in Si MOSFETS?
Fu-Chun Zhang,T. M. Rice
Physics , 1997,
Abstract: This is a comment on a paper published by V. Dobrosavljevic et al. in Phys. Rev. Lett. 79, 455 (1997).
Vortex Structures in Model p-Wave Superconducting Sr2RuO4 -- Single 2-Dimensional Band v.s. Quasi-1-Dimensional Band
J. Huo,Fu-Chun Zhang
Physics , 2013, DOI: 10.1103/PhysRevB.87.134501
Abstract: There have been an interesting debate on the primary source of chiral p-wave superconductivity in Sr2RuO4. We present a comparative study on the vortex structure between a single 2-dimensional (2D) band and quasi-1D band model by using Bogoliubov-de Gennes theory. The pattern of the iso-values of the local density of state around a vortex has a diamond shape in the quasi-1D model and is much more isotropic in the 2D model. The spin lattice relaxation rate well below the superconducting transition temperature is greatly enhanced in the vortex state in the 2D model but not in the quasi-1D model. These features can be tested by using scanning tunneling microscope and NMR to distinguish the models for the superconductivity in Sr2RuO4.
Light Induced Hall effect in semiconductors with spin-orbit coupling
Xi Dai,Fu-Chun Zhang
Physics , 2006, DOI: 10.1103/PhysRevB.76.085343
Abstract: We show that optically excited electrons by a circularly polarized light in a semiconductor with spin-orbit coupling subject to a weak electric field will carry a Hall current transverse to the electric field. This light induced Hall effect is a result of quantum interference of the light and the electric field, and can be viewed as a physical consequence of the spin current induced by the electric field. The light induced Hall conductance is calculated for the p-type GaAs bulk material, and the n-type and p-type quantum well structures.
Optimal Control of Stochastic Magnetization Dynamics by Spin Current
Yong Wang,Fu-Chun Zhang
Physics , 2012, DOI: 10.1209/0295-5075/102/47001
Abstract: Fluctuation-induced stochastic magnetization dynamics plays an important role in magnetic recording and writing. Here we propose that the magnetization dynamics can be optimally controlled by the spin current to minimize or maximize the Freidlin-Wentzell action functional of the system hence to increase or decrease the happening probability of the rare event. We apply this method to study thermal-driven magnetization switching problem and to demonstrate the advantage of the optimal control strategy.
China''s flower calendar and reconstruction of climate in 6th century in China
花信风与我国公元六世纪气候的重建

ZHANG Fu-chun,
张福春

地理研究 , 1999,
Abstract: In this paper, the origin of China's flower calendar is analyzed, it showed that earliest China's flower calendar is emerge in 6th century in Jingzhou, and the climate of 6th century in China is reconstructed using the data from flower calendar. The result showed it was warmer in the 6th century in winter and spring, and it was similar in summer compare with that of the present.
Quantum Monte-Carlo study of a two-species boson Hubbard model
Siegfried Guertler,Matthias Troyer,Fu-Chun Zhang
Physics , 2007, DOI: 10.1103/PhysRevB.77.184505
Abstract: We consider a two-species hard-core boson Hubbard model for a supersolid, where the two types of bosons represent vacancies and interstitials doped into a commensurate crystal. The on-site inter-species interaction may create bound states of vacancies and interstitials facilitating vacancy condensation at lower energies than in a single-species model, as suggested in an earlier mean field study. Here we carry out quantum Monte Carlo simulation to study possible supersolid phases of the model, corresponding to superfluid phases of the vacancies or interstitials. At low temperatures, we find three distinct superfluid phases. The extent of the phases and the nature of the phase transitions are discussed in comparison to mean-field theory.
Observation of Exciton-Phonon Sideband in Individual Metallic Single-Walled Carbon Nanotubes
Hualing Zeng,Hongbo Zhao,Fu-Chun Zhang,Xiaodong Cui
Physics , 2008, DOI: 10.1103/PhysRevLett.102.136406
Abstract: Single-walled carbon nanotubes (SWCNTs) are quasi-one-dimensional systems with poor Coulomb screening and enhanced electron-phonon interaction, and are good candidates for excitons and exciton-phonon couplings in metallic state. Here we report back scattering reflection experiments on individual metallic SWCNTs. An exciton-phonon sideband separated by 0.19 eV from the first optical transition peak is observed in a metallic SWCNT of chiral index (13,10), which provides clear evidences of excitons in metallic SWCNTs. A static dielectric constant of 10 is estimated from the reflectance spectrum.
Variational Monte-Carlo studies of Gossamer Superconductivity
Siegfried Guertler,Qiang-Hua Wang,Fu-Chun Zhang
Physics , 2008, DOI: 10.1103/PhysRevB.79.144526
Abstract: We use a partially Gutzwiller projected BCS d-wave wavefunction with an antiferromagentic weighting factor to study the ground state phase diagram of a half filled Hubbard-Heisenberg model in a square lattice with nearest neighbor hopping $t$ and a diagonal hopping $t'$. The calculations are carried out by using variational Monte Carlo method which treats the Gutzwiller projection explicitly. At large on-site Coulomb interaction $U$, the ground state is antiferromagnetic. As $U$ decreases, the ground state becomes superconducting and eventually metallic. The phase diagram is obtained by extensive calculations. As compared to the strong effect of $U/t$, the phase boundaries turn out to be less sensitive to $t'/t$. The result is consistent with the phase diagram in layered organic conductors, and is compared to the earlier mean field result based on the Gutzwiller approximation.
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