Cooling of strange stars in the color-flavor locked phase with a rotating crust Cooling of strange stars in the color-flavor locked phase with a rotating crust

The presence of the color-flavor locked (CFL) phase strongly suppresses the neutrino emission processes and the quark specific heat. As a result the cooling of the strange stars in the CFL phase is dominated by deconfinement heating and surface emission. The temperature of these stars with strong magnetic field ($B{\geq}10^{10}G$) rise significantly during the first several ten or hundred years, which may be an effective signature of strange stars as implicated by pulsar 0540-69. Furthermore a limit line is predicted, which means compact stars have an upper limit temperature at any moment. We still may search for the candidates for strange stars in the CFL phase along the limit line. The presence of the color-flavor locked (CFL) phase strongly suppresses the neutrino emission processes and the quark specific heat. As a result the cooling of the strange stars in the CFL phase is dominated by deconfinement heating and surface emission. The temperature of these stars with strong magnetic field ($B{\geq}10^{10}G$) rise significantly during the first several ten or hundred years, which may be an effective signature of strange stars as implicated by pulsar 0540-69. Furthermore a limit line is predicted, which means compact stars have an upper limit temperature at any moment. We still may search for the candidates for strange stars in the CFL phase along the limit line.Comment: 9 pages, 3 figures 9 pages, 3 figure

Two-hole ground state wavefunction: Non-BCS pairing in a tt-JJ two-leg ladder system

Superconductivity is usually described in the framework of the Bardeen-Cooper-Schrieffer (BCS) wavefunction, which even includes the resonating-valence-bond (RVB) wavefunction proposed for the high-temperature superconductivity in the cuprate. A natural question is \emph{if} any fundamental physics could be possibly missed by applying such a scheme to strongly correlated systems. Here we study the pairing wavefunction of two holes injected into a Mott insulator/antiferromagnet in a two-leg ladder using variational Monte Carlo (VMC) approach. By comparing with density matrix renormalization group (DMRG) calculation, we show that a conventional BCS or RVB pairing of the doped holes makes qualitatively wrong predictions and is incompatible with the fundamental pairing force in the $t$-$J$ model, which is kinetic-energy-driven by nature. By contrast, a non-BCS-like wavefunction incorporating such novel effect will result in a substantially enhanced pairing strength and improved ground state energy as compared to the DMRG results. We argue that the non-BCS form of such a new ground state wavefunction is essential to describe a doped Mott antiferromagnet at finite doping.Comment: 11 pages, 5 figure

Hidden spin current in doped Mott antiferromagnets

We investigate the nature of doped Mott insulators using exact diagonalization and density matrix renormalization group methods. Persistent spin currents are revealed in the ground state, which are concomitant with a nonzero total momentum or angular momentum associated with the doped hole. The latter determines a nontrivial ground state degeneracy. By further making superpositions of the degenerate ground states with zero or unidirectional spin currents, we show that different patterns of spatial charge and spin modulations will emerge. Such anomaly persists for the odd numbers of holes, but the spin current, ground state degeneracy, and charge/spin modulations completely disappear for even numbers of holes, with the two-hole ground state exhibiting a d-wave symmetry. An understanding of the spin current due to a many-body Berry-like phase and its impact on the momentum distribution of the doped holes will be discussed.Comment: 9 pages, 9 figures, update second version including more data and discussion adde