Optical nanofiber(ONF) is a special tool for effectively controlling coupling of light and atoms. In this paper, we study the ladder-type electromagnetically induced transparent(EIT) under ultralow power level in a wa...Optical nanofiber(ONF) is a special tool for effectively controlling coupling of light and atoms. In this paper, we study the ladder-type electromagnetically induced transparent(EIT) under ultralow power level in a warm cesium vapor by observing the transmission of ONF that couples the 6 S → 6 P Cs atoms in the presence of a 6 P → 8 S control beam through the same fiber. The linewidth and transmission of the EIT signal are investigated at different intensities of the control laser. In addition, we theoretically study the nonlinear interaction at the ONF interface using the multi-level density matrix equations, and obtain good agreements between theory and experiments. The results may have great significance for further study of optical nonlinear effect at low power level.展开更多
We show that a doped spin-1/2 ladder with antiferromagnetic intra-chain and ferromagnetic inter-chain coupling is a symmetry protected topologically non-trivial Luttinger liquid.Turning on a large easy-plane spin anis...We show that a doped spin-1/2 ladder with antiferromagnetic intra-chain and ferromagnetic inter-chain coupling is a symmetry protected topologically non-trivial Luttinger liquid.Turning on a large easy-plane spin anisotropy drives the system to a topologically-trivial Luttinger liquid.Both phases have full spin gaps and exhibit power-law superconducting pair correlation.The Cooper pair symmetry is singlet dxy in the non-trivial phase and triplet Sz? 0 in the trivial phase.The topologically non-trivial Luttinger liquid exhibits gapless spin excitations in the presence of a boundary,and it has no non-interacting or mean-field theory analog even when the fluctuating phase in the charge sector is pinned.As a function of the strength of spin anisotropy there is a topological phase transition upon which the spin gap closes.We speculate these Luttinger liquids are relevant to the superconductivity in metalized integer spin ladders or chains.展开更多
In this Perspective article we review retrospectively the streamline of our work on iron-based superconductors, and reflect on the mechanism of Cooper pairing in conventional and unconventional, such as iron-based sup...In this Perspective article we review retrospectively the streamline of our work on iron-based superconductors, and reflect on the mechanism of Cooper pairing in conventional and unconventional, such as iron-based superconductors. The main theme of this review is the concept of effective interaction and renormalization group.展开更多
By following the Foldy-Wouthuysen(FW)transformation of the Dirac equation,we derive the exact analytic expression up to the 1/M4 order for general cases in the covariant density functional theory.The results are compa...By following the Foldy-Wouthuysen(FW)transformation of the Dirac equation,we derive the exact analytic expression up to the 1/M4 order for general cases in the covariant density functional theory.The results are compared with the corresponding ones derived from another novel non-relativistic expansion method,the similarity renormalization group(SRG).Based on this comparison,the origin of the difference between the results obtained with the FW transformation and the SRG method is explored.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0304203)the National Natural Science Foundation of China(Grant Nos.61675120,11434007,and 61875110)+2 种基金Project of the National Natural Science Foundation of China for Excellent Research Team(Grant No.61121064)the Shanxi “1331 Project” Key Subjects Construction,PCSIRT,China(Grant No.IRT_17R70)the 111 Project,China(Grant No.D18001)
文摘Optical nanofiber(ONF) is a special tool for effectively controlling coupling of light and atoms. In this paper, we study the ladder-type electromagnetically induced transparent(EIT) under ultralow power level in a warm cesium vapor by observing the transmission of ONF that couples the 6 S → 6 P Cs atoms in the presence of a 6 P → 8 S control beam through the same fiber. The linewidth and transmission of the EIT signal are investigated at different intensities of the control laser. In addition, we theoretically study the nonlinear interaction at the ONF interface using the multi-level density matrix equations, and obtain good agreements between theory and experiments. The results may have great significance for further study of optical nonlinear effect at low power level.
基金supported by the U.S.Department of Energy,Office of Science,Office of Advanced Scientific Computing Research,Scientific Discovery through Advanced Computing(SciDAC)program
文摘We show that a doped spin-1/2 ladder with antiferromagnetic intra-chain and ferromagnetic inter-chain coupling is a symmetry protected topologically non-trivial Luttinger liquid.Turning on a large easy-plane spin anisotropy drives the system to a topologically-trivial Luttinger liquid.Both phases have full spin gaps and exhibit power-law superconducting pair correlation.The Cooper pair symmetry is singlet dxy in the non-trivial phase and triplet Sz? 0 in the trivial phase.The topologically non-trivial Luttinger liquid exhibits gapless spin excitations in the presence of a boundary,and it has no non-interacting or mean-field theory analog even when the fluctuating phase in the charge sector is pinned.As a function of the strength of spin anisotropy there is a topological phase transition upon which the spin gap closes.We speculate these Luttinger liquids are relevant to the superconductivity in metalized integer spin ladders or chains.
文摘In this Perspective article we review retrospectively the streamline of our work on iron-based superconductors, and reflect on the mechanism of Cooper pairing in conventional and unconventional, such as iron-based superconductors. The main theme of this review is the concept of effective interaction and renormalization group.
基金Partially supported by the JSPS Grant-in-Aid for Early-Career Scientists(18K13549)the JSPS-NSFC Bilateral Program for Joint Research Project on Nuclear mass and life for unravelling mysteries of the r-processRIKEN Pioneering Project:Evolution of Matter in the Universe
文摘By following the Foldy-Wouthuysen(FW)transformation of the Dirac equation,we derive the exact analytic expression up to the 1/M4 order for general cases in the covariant density functional theory.The results are compared with the corresponding ones derived from another novel non-relativistic expansion method,the similarity renormalization group(SRG).Based on this comparison,the origin of the difference between the results obtained with the FW transformation and the SRG method is explored.
