Mott transition

About: Mott transition is a research topic. Over the lifetime, 2444 publications have been published within this topic receiving 78401 citations.

Optical shutter for laser or maser modulation

Abstract: AN OPTICAL SHUTTER WHICH IS ADAPTED TO MODULATE A LASER OR MASER OR SIMILAR DEVICE IS SHOWN. THE SHUTTER INCLUDES A POLYCONDUCTING DEVICE HAVING A NORMALLY TRANSLUCENT MEMBER AND A METALLIC OXIDE OR METALLIC SALT DIPOSED THEREUPON. THE METALLIC OXIDE OR SALT IS ADAPTED TO UNDERGO A MOTT TRANSITION UPON APPLICATION OF AN IMPRESSED EMF BY INTERNAL HEATING AND IS TRANSLUCENT BELOW THE MOTT TRANSITION POINT BUT IS REFLECTIVE ABOVE THIS POINT. A SIGNAL GENERATION DEVICE IS COUPLED TO THE METALLIC OXIDE OR SALT AND THE SINGLE PRODUCED IS DESIGNED TO BRING THE METALLIC OXIDE OR SALT TO OPPOSITE SIDES OF THE MOTT TRANSITION POINT.

Robust gapless superconductivity in 4 H b − TaS 2

Abstract: The superconducting transition metal dichalcogenide (TMD) $4Hb\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ consists of alternating layers of $H$ and $T$ structures, which in their bulk form are metallic and Mott insulating, respectively. Recently, this compound has been proposed as a candidate chiral superconductor, due to an observed enhancement of the muon-spin relaxation at ${T}_{c}$. $4Hb\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ also exhibits a puzzling $T$-linear specific heat at low temperatures, which is unlikely to be caused by disorder. Elucidating the origin of this behavior is an essential step in discerning the true nature of the superconducting ground state. Here, we propose a simple model that attributes the $T$-linear specific heat to the emergence of a robust multiband gapless superconducting state. We show that an extended regime of gapless superconductivity naturally appears when the pair-breaking scattering rate on distinct Fermi-surface pockets differs significantly, and the pairing interaction is predominantly intrapocket. Using a tight-binding model derived from first-principle calculations, we show that the pair-breaking scattering rate promoted by slow magnetic fluctuations on the $T$ layers, which arise from proximity to a Mott transition, can be significantly different in the various $H$-layer dominated Fermi pockets depending on their hybridization with $T$-layer states. Thus, our results suggest that the ground state of $4Hb\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ consists of Fermi pockets displaying gapless superconductivity, which are shunted by superconducting Fermi pockets that are nearly decoupled from the $T$ layers.

Theory for Quartet Condensation in Fermi Systems with Applications to Nuclei and Nuclear Matter

Abstract: The theory of quartet condensation is further developed. The onset of quartetting in homgeneous fermionic matter is studied with the help of an in-medium modified four fermion equation. It is found that at very low density quartetting wins over pairing. At zero temperature, in analogy to pairing, a set of equations for the quartet order parameter is given. Contrary to pairing, quartetting only exists for strong coupling and breaks down for weak coupling. Reasons for this finding are detailed. In an application to nuclear matter, the critical temperature for alpha particle condensation can reach values up to around 8 MeV. The disappearance of alpha particles with increasing density, i.e. the Mott transition, is investigated. In finite nuclei the Hoyle state, that is the second 0+ state of 12C is identified as an 'alpha-particle condensate' state. It is conjectured that such states also exist in heavier n-alpha nuclei, like 16O, 20Ne, etc. The sixth 0+ state in 16O is proposed as an analogue to the Hoyle state. The Gross-Pitaevski equation is employed to make an estimate of the maximum number of alpha particles a condensate state can contain. Possible quartet condensation in other systems is discussed briefly.

Localized-Itinerant and Mott–Hubbard Transitions in Several Perovskites

Abstract: The localized-itinerant and Mott–Hubbard transitions in single-valent perovskites are distinguished. The approach to the Mott–Hubbard transition from the itinerant-electron side is characterized by the appearance of strong-correlation fluctuations within a metallic matrix; these fluctuations introduce a Curie–Weiss paramagnetism that is added to a strongly enhanced Pauli paramagnetism. As the critical bandwidth is approached, ordering of the strong-correlation fluctuations into a charge-density wave (CDW) may compete with a global Mott-Hubbard transition. The approach to the localized-itinerant electronic transition from the localized-electron side is illustrated by LaMnO3, where orbital ordering localizes the electrons of e-orbital parentage. In the mixed-valent La1−x Sr x MnO3 system, the doped holes evolve from small polarons to two-manganese Zener polarons to itinerant-electron behavior. The Zener polarons order at low temperatures into a CDW.

A direct transition between a Neel ordered Mott insulator and a $d_{x^2-y^2}$ superconductor on the square lattice

Abstract: In this paper we study a bandwidth-controlled direct, continuous, phase transition from a Mott insulator, with easy plane Neel order, to a fully gapped $d_{x^2-y^2}$ superconductor with a doubled unit cell on the square lattice, a transition that is forbidden according to the Landau paradigm. This transition is made possible because the vortices of the antiferromagnet are charged and the vortices of the superconductor carry spins. These nontrivial vortex quantum numbers arise because the ordered phases are intimately related to a topological band insulator. We describe the lattice model as well as the effective field theory.