Department of Physics
Researcher:
Yan Chen, Department of Physics, Fudan University (yanchen99@fudan.edu.cn)
Chen Chen, PhD Student (h0792053@hkusua.hku.hk)
Wonkee Kim, Department of Physics, University of Houston (wonkee.kim@gmail.com)
Zi-Dan Wang, Chair Professor (zwang@hkucc.hku.hk)
Chin-Sen Ting, Department of Physics, University of Houston (ting@uh.edu)
Project Title:
Theory of Phase Fluctuations in the Pseudogap of Cuprate Superconductors
Project Description:
Within the phase fluctuation picture for the pseudogap state of cuprate superconductors, we study effects of the thermal phase fluctuations generated by the classical XY model.
Project Duration:
1 years
Project Significance:
Recently,there is a growing interest in studying the pseudogap region of high-temperature superconductors. This fastinating phase existes above Tc and serves as the normal state of a superconductor across a broad range of hole densities in the underdoped regime. Many theoretical models have been introduced to explain this exotic phase, while generally they fall into two categories. In the first viewpoint, pseudogap is considered to be another energy scale, i.e. another state that competing with the superconducting state. Possible candidates are charege density wave (CDW), spin density wave (SDW) or etc. The other one is the pre-formed pair picture, i.e. in the pseudogap region electron pairing still exist but without long range phase coherence. In this scenario, the transition between superconducting state to pseudogap region is consider to be a Berezinsky-Kosterlitz-Thouless (BKT) transition, while the BCS mean-field transition temperature correspond to T*.
Many experiments have been found to support the preformed-pairing viewpoint.
More quantitativly, Fermi arc length are found to be linearly scaling as temperature increases, and the leading-edge gap size along the Fermi surface are found to be deviated from that in d-wave superconducting state.
Results Achieved:
Both the temperature dependence of the arc length and momentum dependence of the gap function have been investigated. We compute the local density of states near a non-magnetic impurity with a strong scattering potential. The resonance peak smoothly evolves as temperature increases through Tc, which is consistent with recent experimental findings for an overdoped material. We also predict that for an optimally doped case the peak will be washed away well below Tc. All these results are consistent with recent APRES and STM experimental measurements.
Submitted to Physical Review Letters
Remarks on the Use of High Performance Computing Clusters:
Several sets of data is obtained with the support of hpcpower2. We use C++ and Matlab in this project, in which one program has to be run with a huge number of different parameters. Our serial program is modified by Mr. Kwan WK to become a parallel one.
