METAL–INSULATOR TRANSITION OF THE SPINLESS FERMIONS ON THE KAGOMÉ LATTICE

2011 ◽  
Vol 25 (12n13) ◽  
pp. 947-953 ◽  
Author(s):  
MASAAKI NAKAMURA ◽  
SATOSHI NISHIMOTO ◽  
AROON O'BRIEN ◽  
PETER FULDE
Keyword(s):  
Nearest Neighbor ◽  
Random Phase ◽  
Insulator Transition ◽  
Kagome Lattice ◽  
Qualitative Properties ◽  
Metal Insulator Transition ◽  
Coupling Region ◽  
Metal Insulator ◽  
Kagomé Lattice ◽  
Spinless Fermion

We discuss the metal–insulator transition of the spinless fermion model with nearest-neighbor repulsion on the Kagomé lattice at 1/3- and 2/3-filling. The system is analyzed by using exact diagonalization, the density-matrix renormalization group methods and the random phase approximation. In the strong-coupling region, the system is described by ring exchange processes. In the intermediate-coupling regime, we find that the qualitative properties of the metal–insulator transition at 1/3- and 2/3-filling are totally different reflecting the difference in the band structure near the Fermi level.

Metal-Insulator Transition of Fermions on a Kagome Lattice at 1/3 Filling

2010 ◽  
Vol 104 (19) ◽  
Author(s):  
Satoshi Nishimoto ◽  
Masaaki Nakamura ◽  
Aroon O’Brien ◽  
Peter Fulde
Keyword(s):  
Insulator Transition ◽  
Kagome Lattice ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Kagomé Lattice

scholarly journals EFFECT OF STRAIN ON THE TRANSPORT PROPERTIES OF THE MANGANITE

2001 ◽  
Vol 15 (27) ◽  
pp. 3551-3558 ◽  
Author(s):  
S. BASAK ◽  
I. CHAUDHURI ◽  
S. K. GHATAK
Keyword(s):  
Magnetic Field ◽  
Nearest Neighbor ◽  
Large Strain ◽  
Spin Correlation ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Increasing Function

The effect of strain on the resistivity and thermopower of ferromagnetic manganites has been examined based on the model that incorporates the electron-lattice interaction through the Jahn–Teller effect and an effective hopping determined by nearest neighbor spin–spin correlation of t2g electrons. The metal insulator transition temperature associated with resistivity decreases with increase in strain. In the presence of large strain the system remains in the semiconducting state. Thermopower (S) is positive and increasing function of strain and it exhibits a maximum with temperature. The temperature where maximum of S appears, shifts towards higher (lower) value in the presence of magnetic field (strain). A large magneto-thermopower that depends on strain is obtained around metal–insulator transition.

scholarly journals Advanced First-Principle Modeling of Relativistic Ruddlesden—Popper Strontium Iridates

2021 ◽  
Vol 11 (6) ◽  
pp. 2527
Author(s):  
Peitao Liu ◽  
Cesare Franchini
Keyword(s):  
Magnetic Properties ◽  
Random Phase ◽  
Insulator Transition ◽  
Field Energy ◽  
Local Spin Density Approximation ◽  
First Principle ◽  
Spin Orbit ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Hubbard U

In this review, we provide a survey of the application of advanced first-principle methods on the theoretical modeling and understanding of novel electronic, optical, and magnetic properties of the spin-orbit coupled Ruddlesden–Popper series of iridates Srn+1IrnO3n+1 (n = 1, 2, and ∞). After a brief description of the basic aspects of the adopted methods (noncollinear local spin density approximation plus an on-site Coulomb interaction (LSDA+U), constrained random phase approximation (cRPA), GW, and Bethe–Salpeter equation (BSE)), we present and discuss select results. We show that a detailed phase diagrams of the metal–insulator transition and magnetic phase transition can be constructed by inspecting the evolution of electronic and magnetic properties as a function of Hubbard U, spin–orbit coupling (SOC) strength, and dimensionality n, which provide clear evidence for the crucial role played by SOC and U in establishing a relativistic (Dirac) Mott–Hubbard insulating state in Sr2IrO4 and Sr3Ir2O7. To characterize the ground-state phases, we quantify the most relevant energy scales fully ab initio—crystal field energy, Hubbard U, and SOC constant of three compounds—and discuss the quasiparticle band structures in detail by comparing GW and LSDA+U data. We examine the different magnetic ground states of structurally similar n = 1 and n = 2 compounds and clarify that the origin of the in-plane canted antiferromagnetic (AFM) state of Sr2IrO4 arises from competition between isotropic exchange and Dzyaloshinskii–Moriya (DM) interactions whereas the collinear AFM state of Sr3Ir2O7 is due to strong interlayer magnetic coupling. Finally, we report the dimensionality controlled metal–insulator transition across the series by computing their optical transitions and conductivity spectra at the GW+BSE level from the the quasi two-dimensional insulating n = 1 and 2 phases to the three-dimensional metallic n=∞ phase.

Particle Size Dependent Magnetoresistance And Magnetothermoelectric Power Of La0.5Pb0.5MnO3 Showing Metal-Insulator Transition

2002 ◽  
Vol 718 ◽  
Author(s):  
Aritra Banerjee ◽  
S Pal ◽  
B K Chaudhuri
Keyword(s):  
Magnetic Field ◽  
Particle Size ◽  
Low Temperature ◽  
Nearest Neighbor ◽  
Small Polaron ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Polaron Hopping ◽  
Size Dependent

AbstractParticle size dependent transport properties (resistivity and thermopower) of La0.5Pb0.5MnO3 has been investigated both in presence and in absence of magnetic field B=0.0-1.5T (maximum). All the samples show metal-insulator transition (MIT) with a peak at the MIT temperature (Tp). Magnetic field decreases the resistivity with an increase in the peak temperature Tp. Particle size, conductivity and Tp of the sample increase with increasing annealing time. High temperature semiconducting (insulating) part of the resistivity curve is divided into two distinct regimes. Resistivity data for T>qθ/2, can be well fitted with the nearest neighbor small polaron hopping (SPH) model. Polaron hopping energy (WH) decreases with increase of particle size. The lower temperature part (Tp>T>qθ/2) of the semiconducting (insulating) regime is found to follow variable range hopping (VRH) model. With the increase of particle size, the temperature range of validity of the VRH mechanism decreases. The low temperature metallic regime (for T<Tp) of the resistivity (both in absence and in presence of field) data fit well with ρ = ρ0 +ρ2.5 T2.5 and transport mechanism in this region is mainly dominated by magnon-carrier scattering (∼T2.5). Particle size has, however, comparatively little effect on Seebeck coefficient (S). In all the samples with different particle sizes, S changes sign below Tp. In contrast to magnetoresistance, application of magnetic field increases S at low temperature (T<Tp) for these samples. Similar to the resistivity results, thermopower data in the metallic phase (both for B=0.0 and 1.5T) can also be analyzed by considering magnon-scattering term along with an additional spin-wave fluctuation term (∼T4).

Sign in / Sign up

Export Citation Format

Share Document