16 research outputs found
Influence of long-range interactions on charge ordering phenomena on a square lattice
Usually complex charge ordering phenomena arise due to competing
interactions. We have studied how such ordered patterns emerge from the
frustration of a long-ranged interaction on a lattice. Using the lattice gas
model on a square lattice with fixed particle density, we have identified
several interesting phases; such as a generalization of Wigner crystals at low
particle densities and stripe phases at densities in between rho = 1/3 and rho
= 1/2. These stripes act as domain walls in the checkerboard phase present at
half-filling. The phases are characterised at zero temperatures using numerical
simulations, and mean field theory is used to construct a finite temperature
phase diagram.Comment: 8 pages, 8 figure
Avoiding Stripe Order: Emergence of the Supercooled Electron Liquid
In the absence of disorder, electrons can display glassy behavior through
supercooling the liquid state, avoiding the solidification into a charge
ordered state. Such supercooled electron liquids are experimentally found in
organic - compounds. We present theoretical results that
qualitatively capture the experimental findings. At intermediate temperatures,
the conducting state crosses over into a weakly insulating pseudogap phase. The
stripe order phase transition is first order, so that the liquid phase is
metastable below . In the supercooled liquid phase the resistivity
increases further and the density of states at the Fermi level is suppressed,
indicating kinetic arrest and the formation of a glassy state. Our results are
obtained using classical Extended Dynamical Mean Field Theory.Comment: 4 pages, 4 figures, submitted to the proceedings of "Superstripes
2015", Journal of Superconductivity and Novel Magnetism (2015
Suppressed Density of States in Self-Generated Coulomb Glasses
We investigate the structure of metastable states in self-generated Coulomb
glasses. In dramatic contrast to disordered electron glasses, we find that
these states lack marginal stability. Such absence of marginal stability is
reflected by the suppression of the single-particle density of states into an
exponentially soft gap of the form .
To analytically explain this behavior, we extend the stability criterion of
Efros and Shklovskii to incorporate local charge correlations, in qualitative
agreement with our numerical findings. Our work suggests the existence of a new
class of self-generated glasses dominated by strong geometric frustration.Comment: v3 is the published version in New Journal of Physic
Strong-disorder renormalization-group study of the one-dimensional tight-binding model
We formulate a strong-disorder renormalization-group (SDRG) approach to study
the beta function of the tight-binding model in one dimension with both
diagonal and off-diagonal disorder for states at the band center. We show that
the SDRG method, when used to compute transport properties, yields exact
results since it is identical to the transfer matrix method. The beta function
is shown to be universal when only off-diagonal disorder is present even though
single-parameter scaling is known to be violated. A different single-parameter
scaling theory is formulated for this particular (particle-hole symmetric)
case. Upon breaking particle-hole symmetry (by adding diagonal disorder), the
beta function is shown to crossover from the universal behavior of the
particle-hole symmetric case to the conventional non-universal one in agreement
with the two-parameter scaling theory. We finally draw an analogy with the
random transverse-field Ising chain in the paramagnetic phase. The
particle-hole symmetric case corresponds to the critical point of the quantum
Ising model while the generic case corresponds to the Griffiths paramagnetic
phase.Comment: includes 12 pages, 4 figure
Universal scaling near band-tuned metal-insulator phase transitions
We present a theory for band-tuned metal-insulator transitions based on the
Kubo formalism. Such a transition exhibits scaling of the resistivity curves,
in the regime where or , where is the scattering
time and the chemical potential. At the critical value of the chemical
potential, the resistivity diverges as a power law, .
Consequently, on the metallic side there is a regime with negative ,
which is often misinterpreted as insulating. We show that scaling and this
`fake insulator' regime is observed in a wide range of experimental systems. In
particular, we show that Mooij correlations in high-temperature metals with
negative can be quantitatively understood with our scaling theory in
the presence of -linear scattering.Comment: 10 pages, 7 figure
Effective Cluster Typical Medium Theory for Diagonal Anderson Disorder Model in One- and Two-Dimensions
We develop a cluster typical medium theory to study localization in
disordered electronic systems. Our formalism is able to incorporate non-local
correlations beyond the local typical medium theory in a systematic way. The
cluster typical medium theory utilizes the momentum resolved typical density of
states and hybridization function to characterize the localization transition.
We apply the formalism to the Anderson model of localization in one- and
two-dimensions. In one dimension, we find that the critical disorder strength
scales inversely with the linear cluster size with a power-law, ; whereas in two dimensions, the critical disorder strength
decreases logarithmically with the linear cluster size. Our results are
consistent with previous numerical work and in agreement with the one-parameter
scaling theory.Comment: 8 Pages and 8 Figure
How to recognize the universal aspects of Mott criticality?
In this paper we critically discuss several examples of two-dimensional
electronic systems displaying interaction-driven metal-insulator transitions of
the Mott (or Wigner--Mott) type, including dilute two-dimension electron gases
(2DEG) in semiconductors, Mott organic materials, as well as the recently
discovered transition-metal dichalcogenide (TMD) moir\'e bilayers. Remarkably
similar behavior is found in all these systems, which is starting to paint a
robust picture of Mott criticality. Most notable, on the metallic side a
resistivity maximum is observed whose temperature scale vanishes at the
transition. We compare the available experimental data on these systems to
three existing theoretical scenarios: spinon theory, Dynamical Mean Field
Theory (DMFT) and percolation theory. We show that the DMFT and percolation
pictures for Mott criticality can be distinguished by studying the origins of
the resistivity maxima using an analysis of the dielectric response.Comment: Contribution to Special Issue "New Spin on Metal-Insulator
Transitions" in Crystals, Guest Editor: A. Pustogo
Conductor-insulator quantum phase transitions
When many particles come together how do they organise themselves? And what destroys this organisation? Combining experiments and theory, this book describes intriguing quantum phases - metals, superconductors and insulators - and transitions between them
Quantum critical scaling for finite-temperature Mott-like metal-insulator crossover in few-layered MoS2
The dominant role of strong electron-electron interactions in driving two-dimensional metal-insulator transitions has long been debated, but its clear experimental demonstration is still not available. Here, we examine the finite-temperature transport behavior of few-layered MoS2 material in the vicinity of the density-driven metal-insulator transition, revealing previously overlooked universal features characteristic of strongly correlated electron systems. Our scaling analysis, based on the Wigner-Mott theoretical viewpoint, conclusively demonstrates that the transition is driven by strong electron-electron interactions and not disorder, in striking resemblance to what is seen in other Mott systems. Our results provide compelling evidence that transition-metal dichalcogenides provide an ideal testing ground, and should open an exciting avenue for the study of strong correlation physics.11Nsciescopu