M. J. Rozenberg

Strong electron correlation effects in nonvolatile electronic memory devices

We propose a theoretical domain-tunneling (DT) model of the resistance switching phenomenon that is often experimentally observed in metal-semiconductor-metal sandwich structures which is considered as a possible non-volatile memory devices. The DT model is incorporated with a metal-insulator transition due to strong electron correlations at the semiconductor/metal interface. We have also prepared experimentally a Pt/NiO/Pt test device and have observed the resistance switching. The calculated results of the DT model are compared to the experimental results, manifesting that this sandwich structure could be the realisation of a novel strongly correlated electron device

Finite Temperature Mott Transition in the Hubbard Model in Infinite Dimensions

We study the second order finite temperature Mott transition point in the fully frustrated Hubbard model at half filling, within Dynamical Mean Field Theory. Using quantum Monte Carlo simulations we show the existence of a finite temperature second order critical point by explicitly demonstrating the existence of a divergent susceptibility as well as by finding coexistence in the low temperature phase. We determine the location of the finite temperature Mott critical point in the (U,T) plane. Our study verifies and quantifies a scenario for the Mott transition proposed in earlier studies (Reviews of Modern Physics 68, 13, 1996) of this problem.

Dynamical mean field theory with the density matrix renormalization group

A new numerical method for the solution of the dynamical mean field theorys self-consistent equations is introduced. The method uses the density matrix renormalization group technique to solve the associated impurity problem. The new algorithm makes no a priori approximations and is only limited by the number of sites that can be considered. We obtain accurate estimates of the critical values of the metal-insulator transitions and provide evidence of substructure in the Hubbard bands of the correlated metal. With this algorithm, more complex models having a larger number of degrees of freedom can be considered and finite-size effects can be minimized.

Low Frequency Spectroscopy of the Correlated Metallic System CaxSr12xVO3

We study the photoemission and optical conductivity response of the strongly correlated metallic system

First-order insulator-to-metal Mott transition in the paramagnetic 3D system GaTa4Se8.

Ca_xSr_{1-x}VO_3

Enhanced and continuous electrostatic carrier doping on the SrTiO3 surface

. We find that the basic features of the transfer of spectral weight in photoemission experiments and the unusual lineshape of the optical response can be understood by modeling the system with a one band Hubbard model close to the Mott-Hubbard transition. We present a detailed comparison between the low frequency experimental data and the corresponding theoretical predictions obtained within the LISA method that is exact in the limit of large lattice connectivity.

Phase diagram of the asymmetric Hubbard model and an entropic chromatographic method for cooling cold fermions in optical lattices

The nature of the Mott transition in the absence of any symmetry breaking remains a matter of debate. We study the correlation-driven insulator-to-metal transition in the prototypical 3D Mott system GaTa(4)Se(8), as a function of temperature and applied pressure. We report novel experiments on single crystals, which demonstrate that the transition is of first order and follows from the coexistence of two states, one insulating and one metallic, that we toggle with a small bias current. We provide support for our findings by contrasting the experimental data with calculations that combine local density approximation with dynamical mean-field theory, which are in very good agreement.

Quantum Monte Carlo method for models of molecular nanodevices

Paraelectrical tuning of a charge carrier density as high as 1013 cm−2 in the presence of a high electronic carrier mobility on the delicate surfaces of correlated oxides, is a key to the technological breakthrough of a field effect transistor (FET) utilising the metal-nonmetal transition. Here we introduce the Parylene-C/Ta2O5 hybrid gate insulator and fabricate FET devices on single-crystalline SrTiO3, which has been regarded as a bedrock material for oxide electronics. The gate insulator accumulates up to ~1013cm−2 carriers, while the field-effect mobility is kept at 10 cm2/Vs even at room temperature. Further to the exceptional performance of our devices, the enhanced compatibility of high carrier density and high mobility revealed the mechanism for the long standing puzzle of the distribution of electrostatically doped carriers on the surface of SrTiO3. Namely, the formation and continuous evolution of field domains and current filaments.

Weak-coupling study of decoherence of a qubit in disordered magnetic environments

We study the phase diagram of the asymmetric Hubbard model (AHM), which is characterized by different values of the hopping for the two spin projections of a fermion or equivalently, two different orbitals. This model is expected to provide a good description of a mass-imbalanced cold fermionic mixture in a 3D optical lattice. We use the dynamical mean field theory to study various physical properties of this system. In particular, we show how orbital-selective physics, observed in multi-orbital strongly correlated electron systems, can be realized in such a simple model. We find that the density distribution is a good probe of this orbital selective crossover from a Fermi liquid to a non-Fermi liquid state. Below an ordering temperature

Mott transition in the Hubbard model away from particle-hole symmetry

T_o