We describe a new possible route to the metal-insulator transition in doped semiconductors such as Si:P or Si:B. We explore the possibility that the loss of metallic transport occurs through Mott localization of electrons into a quantum spin liquid state with diffusive charge neutral "spinon" excitations. Such a quantum spin liquid state can appear as an intermediate phase between the metal and...

Correlation between structure and transport properties are investigated in high-quality single-crystals of Ca2Ru1 xCrxO4 with 0oxo0.14 using single crystal X-ray diffraction and by electronic studies. The parent compound was known to exhibit an intriguing first-order structurally driven metal–insulator (MI) transition at 357 K. Upon chromium doping on the ruthenium site, the metal–insulator tra...

Wilson’s numerical renormalization group method for the calculation of dynamic properties of impurity models is generalized to investigate the effective impurity model of the dynamical mean-field theory at finite temperatures. We calculate the spectral function and self-energy for the Hubbard model on a Bethe lattice with infinite coordination number directly on the real-frequency axis and inve...

As the thickness or magnetic field is varied in thin films a transition between superconducting and insulating phases takes place. This quantum phase transition obeys scaling relations and occurs at seemingly universal critical resistance. This paper reviews experiments that demonstrate this transition and measure the critical exponents. The microscopic theories are outlined and lead to differe...

In order to clarify the physics of the crossover from a Peierls band insulator to a correlated Mott-Hubbard insulator, we analyze ground-state and spectral properties of the one-dimensional halffilled Holstein-Hubbard model using quasi-exact numerical techniques. In the adiabatic limit the transition is connected to the band to Mott insulator transition of the ionic Hubbard model. Depending on ...

By using a combination of detailed experimental studies and simple theoretical arguments, we identify a novel mechanism characterizing the hopping transport in the Mott insulating phase of Ca2-xSrxRuO4 near the metal-insulator transition. The hopping exponent alpha shows a systematic evolution from a value of alpha=1/2 deeper in the insulator to the conventional Mott value alpha=1/3 closer to t...

The title compound undergoes a metal-insulator phase transition of unknown origm at TMI = 135 K. We studied the electrodynamic response of a-(BEDT~TTF)213

We solve the periodic Anderson model in the Mott-Hubbard regime, using dynamical mean field theory. Upon electron doping of the Mott insulator, a metal-insulator transition occurs which is qualitatively similar to that of the single band Hubbard model, namely, with a divergent effective mass and a first order character at finite temperatures. Surprisingly, upon hole doping, the metal-insulator ...