Pseudogap phenomena and the formation of Fermi arcs in underdoped cuprates are numerically studied in the presence of phase fluctuations that are simulated by an XY model. Most importantly the spectral function for each Monte Carlo sample is calculated directly and efficiently by the Chebyshev polynomials without having to diagonalize the fermion Hamiltonian, which enables us to handle a system large enough to achieve sufficient momentum/energy resolution. We find that the momentum dependence of the energy gap is identical to that of a pure d-wave superconductor well below the KT-transition temperature (TKT), while displays an upturn deviation from cos kx − cos ky with increasing temperature. An abrupt onset of the Fermi arcs is observed above TKT and the arc length exhibits a similar temperature dependence to the thermally activated vortex excitations. PACS numbers:One of the most important open issues in the research of high temperature superconducitity is the origin of the so-called pseudogap and its relation to the superconducting gap. One viewpoint regards the pseudogap as preformed Cooper-pair state without long-range phase coherence, yet another attributes its origin to a new phase of matter. The most direct evidence of the pseudogap in hole-doped cuprates comes from experimental techniques such as angle resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS), which measure the low-energy single-particle spectrum and relate the loss of spectral weight to the pseudogap opening. [1-3] One peculiar property of the pseudogap phase revealed by ARPES is the truncated Fermi surfaces termed as 'Fermi arcs'.[4] The Fermi arcs emerge abruptly around the nodal region above T c , and extend out to the Brillouin zone edge with increasing temperature and form a complete Fermi surface for temperature above T * . [4][5][6] This evolution of the Fermi surface shows a sharp distinction from that of conventional BCS superconductors.The evolution of the Fermi surface in the pseudogap phase has been addressed [7][8][9] within the phase fluctuation context. The formation of Fermi arcs was attributed to the pile-up of low-energy spectral weight due to the Doppler effect of the fluctuating suppercurrent. [7] However such analytic results are based on a semiclassical approximation [10] which was argued to be uncontrolled [11]. Numerical treatment of the effect of phase fluctuations involved a combination of the Monte Carlo (MC) simulation of the Landau-Ginzburg free energy and the exact diagonalization of the fermion Hamiltonian.[8] However, the competition between the superconducting and antiferromagnetic order parameters in the presence of quenched disorder was complicated and the momentum resolution was relative low due to the time-consuming numerical diagonalization procedure.In this work, we 1) examine the momentum and temperature dependence of the spectral gap and 2) temperature dependence of the Fermi-arc length within the phase-fluctuating scenario. The fluctuating phases are simulated phenom...

An all solid state single longitudinal mode (SLM) laser at 500.8 nm with 830 mW output power has been demonstrated for the first time. By using a new resonator for doubly resonant, Nd:GdVO 4 and Nd:YAG were pumped by two laser diode arrays coupled by optical fiber, respectively. In the two sub cavities, SLM wavelengths of 1064 and 946 nm were induced by using the twisted mode technique and then mixed into SLM 500.8 nm laser with sum frequency technology. The SLM 500.8 nm laser output of 830 mW was obtained at the incident pump power of 20 W for Nd:GdVO 4 and 23 W for Nd:YAG. The experimental results showed that the intracavity sum frequency mixing by twisted mode technique is an effective method for SLM 500.8 nm laser.