We report a quantum phase transition between orbital-selective Mott states, with different localized orbitals, in a Hunds metals model. Using the density matrix renormalization group, the phase diagram is constructed varying the electronic density an
d Hubbard $U$, at robust Hunds coupling. We demonstrate that this transition is preempted by charge fluctuations and the emergence of free spinless fermions, as opposed to the magnetically-driven Mott transition. The Luttinger correlation exponent is shown to have a universal value in the strong-coupling phase, whereas it is interaction dependent at intermediate couplings. At weak coupling we find a second transition from a normal metal to the intermediate-coupling phase.
The orbital-selective Mott phase (OSMP) of multiorbital Hubbard models has been extensively analyzed before using static and dynamical mean-field approximations. In parallel, the properties of Block states (antiferromagnetically coupled ferromagnetic
spin clusters) in Fe-based superconductors have also been much discussed. The present effort uses numerically exact techniques in one-dimensional systems to report the observation of Block states within the OSMP regime, connecting two seemingly independent areas of research, and providing analogies with the physics of Double-Exchange models.
The undoped three-orbital spin fermion model for the Fe-based superconductors is studied via Monte Carlo techniques in two-dimensional clusters. At low temperatures, the magnetic and one-particle spectral properties are in good agreement with neutron
and photoemission experiments. Our most important results are the resistance vs. temperature curves that display all the features experimentally observed in BaFe$_2$As$_2$ detwinned single crystals (under uniaxial stress), including a low-temperature anisotropy between the two directions followed by a peak at the magnetic ordering temperature, here induced by short-range spin order and concomitant Fermi Surface orbital order.
This paper analyzes the security of a recent cryptosystem based on the ergodicity property of chaotic maps. It is shown how to obtain the secret key using a chosen-ciphertext attack. Some other design weaknesses are also shown.
A large number of analog chaos-based secure communication systems have been proposed since the early 1990s exploiting the technique of chaos synchronization. A brief survey of these chaos-based cryptosystems and of related cryptanalytic results is gi
ven. Some recently proposed countermeasures against known attacks are also introduced.
