116 research outputs found
Renormalization group study of a two-valley system with spin-splitting
Renormalization group equations in a two-valley system with valley-splitting
and intervalley scattering are derived in the presence of spin-splitting
induced by a parallel magnetic field. The relevant amplitudes in different
regimes set by the relative strengths of the spin and valley splittings and the
intervalley scattering rate are identified. The range of applicability of the
standard formula for the magnetoconductance is discussed
Renormalization group study of intervalley scattering and valley splitting in a two-valley system
Renormalization group equations are derived for the case when both valley
splitting and intervalley scattering are present in a two-valley system. A
third scaling parameter is shown to be relevant when the two bands are split
but otherwise distinct. The existence of this parameter changes the
quantitative behavior at finite temperatures, but the qualitative conclusions
of the two-parameter theory are shown to be unaffected for realistic choice of
parameters
Test of scaling theory in two dimensions in the presence of valley splitting and intervalley scattering in Si-MOSFETs
We show that once the effects of valley splitting and intervalley scattering
are incorporated, renormalization group theory consistently describes the
metallic phase in silicon metal-oxide-semiconductor field-effect transistors
down to the lowest accessible temperatures
Correlation function for the one-dimensional extended Hubbard model at quarter filling
We examine the density-density correlation function in the Tomonaga-Luttinger
liquid state for the one-dimensional extended Hubbard model with the on-site
Coulomb repulsion and the intersite repulsion at quarter filling. By
taking into account the effect of the marginally irrelevant umklapp scattering
operator by utilizing the renormalization-group technique based on the
bosonization method, we obtain the generalized analytical form of the
correlation function. We show that, in the proximity to the gapped
charge-ordered phase, the correlation function exhibits anomalous crossover
between the pure power-law behavior and the power-law behavior with logarithmic
corrections, depending on the length scale. Such a crossover is also confirmed
by the highly-accurate numerical density-matrix renormalization group method.Comment: 6 pages, 3 figure
Zero bias anomaly out of equilibrium
The non-equilibrium zero bias anomaly (ZBA) in the tunneling density of
states of a diffusive metallic film is studied. An effective action describing
virtual fluctuations out-of-equilibrium is derived. The singular behavior of
the equilibrium ZBA is smoothed out by real processes of inelastic scattering.Comment: 4 page
Chiral spin resonance and spin-Hall conductivity in the presence of the electron-electron interactions
We discuss the electron spin resonance in two-dimensional electron gas at
zero external magnetic field. This spin-resonance is due to the transitions
between the electron states, which are split by the spin-orbit (SO)
interaction, and is termed as the chiral spin resonance (CSR). It can be
excited by the in-plane component of the electric field of microwave radiation.
We show that there exists an inherent relationship between the spin-Hall
conductivity and the CSR in a system with the SO interaction. Since in the
presence of the SO interaction spin is not conserved, the electron-electron
interaction renormalizes the spin-Hall conductivity as well as the frequency of
the CSR. The effects of the electron interaction in systems with the SO
interaction are analyzed both phenomenologically and microscopically.Comment: 14 page
Coulomb Blockade of Proximity Effect at Large Conductance
We consider the proximity effect in a normal dot coupled to a bulk
superconducting reservoir by the tunnel contact with large normal conductance.
Coulomb interaction in the dot suppresses the proximity minigap induced in the
normal part of the system. We find exact expressions for the thermodynamic and
tunneling minigaps as functions of the junction's capacitance. The tunneling
minigap interpolates between its proximity-induced value in the regime of weak
Coulomb interaction to the Coulomb gap in the regime of strong interaction. In
the intermediate case a non-universal two-step structure of the tunneling
density of states is predicted. The charge quantization in the dot is also
studied.Comment: 4 pages (RevTeX), 3 figures. Version 2: minor corrections, a figure
and two references adde
Flow diagram of the metal-insulator transition in two dimensions
The discovery of the metal-insulator transition (MIT) in two-dimensional (2D)
electron systems challenged the veracity of one of the most influential
conjectures in the physics of disordered electrons, which states that `in two
dimensions, there is no true metallic behaviour'; no matter how weak the
disorder, electrons would be trapped and unable to conduct a current. However,
that theory did not account for interactions between the electrons. Here we
investigate the interplay between the electron-electron interactions and
disorder near the MIT using simultaneous measurements of electrical resistivity
and magnetoconductance. We show that both the resistance and interaction
amplitude exhibit a fan-like spread as the MIT is crossed. From these data we
construct a resistance-interaction flow diagram of the MIT that clearly reveals
a quantum critical point, as predicted by the two-parameter scaling theory
(Punnoose and Finkel'stein, Science 310, 289 (2005)). The metallic side of this
diagram is accurately described by the renormalization group theory without any
fitting parameters. In particular, the metallic temperature dependence of the
resistance sets in when the interaction amplitude reaches gamma_2 = 0.45 - a
value in remarkable agreement with the one predicted by the theory.Comment: as publishe
Graphene via large N I: Renormalization
We analyze the competing effects of moderate to strong Coulomb
electron-electron interactions and weak quenched disorder in graphene. Using a
one-loop renormalization group calculation controlled within the large-N
approximation, we demonstrate that, at successively lower energy (temperature
or chemical potential) scales, a type of non-Abelian vector potential disorder
always asserts itself as the dominant elastic scattering mechanism for generic
short-ranged microscopic defect distributions. Vector potential disorder is
tied to both elastic lattice deformations ("ripples") and topological lattice
defects. We identify several well-defined scaling regimes, for which we provide
scaling predictions for the electrical conductivity and thermopower, valid when
the inelastic lifetime due to interactions exceeds the elastic lifetime due to
disorder. Coulomb interaction effects should figure strongly into the physics
of suspended graphene films, where rs > 1; we expect vector potential disorder
to play an important role in the description of transport in such films.Comment: 25 pages, 21 figure
Boson-assisted tunneling in layered metals
A theory for boson-assisted tunneling via randomly distributed resonant
states in a layered metals is developed. As particular examples, we consider
the electron-phonon interaction and the interaction between localized and
conduction electrons. The theory is applied to explain a non-monotonic
variation of the out-plane resistivity with temperature observed in
quasi-two-dimensional metals.Comment: 14 pages, 5 figure
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