434 research outputs found
Interchain-Frustration-Induced Metallic State in Quasi-One-Dimensional Mott Insulators
The mechanism that drives a metal-insulator transition in an undoped
quasi-one-dimensional Mott insulator is examined in the framework of the
Hubbard model with two different hoppings t_{perp 1} and t_{perp 2} between
nearest-neighbor chains. By applying an N_{perp}-chain renormalization group
method at the two-loop level, we show how a metallic state emerges when both
t_{perp 1} and t_{perp 2} exceed critical values. In the metallic phase, the
quasiparticle weight becomes finite and develops a strong momentum dependence.
We discuss the temperature dependence of the resistivity and the impact of our
theory in the understanding of recent experiments on half-filled molecular
conductors.Comment: 4 pages, 3 figures, published versio
Superconducting pairing and density-wave instabilities in quasi-one-dimensional conductors
Using a renormalization group approach, we determine the phase diagram of an
extended quasi-one-dimensional electron gas model that includes interchain
hopping, nesting deviations and both intrachain and interchain repulsive
interactions. d-wave superconductivity, which dominates over the
spin-density-wave (SDW) phase at large nesting deviations, becomes unstable to
the benefit of a triplet -wave phase for a weak repulsive interchain
backscattering term , despite the persistence of dominant SDW
correlations in the normal state. Antiferromagnetism becomes unstable against
the formation of a charge-density-wave state when exceeds some
critical value. While these features persist when both Umklapp processes and
interchain forward scattering () are taken into account, the effect
of alone is found to frustrate nearest-neighbor interchain - and
-wave pairing and instead favor next-nearest-neighbor interchain singlet or
triplet pairing. We argue that the close proximity of SDW and
charge-density-wave phases, singlet d-wave and triplet -wave superconducting
phases in the theoretical phase diagram provides a possible explanation for
recent puzzling experimental findings in the Bechgaard salts, including the
coexistence of SDW and charge-density-wave phases and the possibility of a
triplet pairing in the superconducting phase.Comment: 19 pages, 13 figure
Microwave dielectric study of spin-Peierls and charge ordering transitions in (TMTTF)PF salts
We report a study of the 16.5 GHz dielectric function of hydrogenated and
deuterated organic salts (TMTTF)PF. The temperature behavior of the
dielectric function is consistent with short-range polar order whose relaxation
time decreases rapidly below the charge ordering temperature. If this
transition has more a relaxor character in the hydrogenated salt, charge
ordering is strengthened in the deuterated one where the transition temperature
has increased by more than thirty percent. Anomalies in the dielectric function
are also observed in the spin-Peierls ground state revealing some intricate
lattice effects in a temperature range where both phases coexist. The variation
of the spin-Peierls ordering temperature under magnetic field appears to follow
a mean-field prediction despite the presence of spin-Peierls fluctuations over
a very wide temperature range in the charge ordered state of these salts.Comment: 7 pages, 6 figure
CDW Ordering in Stripe Phase of Underdoped Cuprates
The in-plane resistivity and out-of-plane resistivity of non-superconducting
RBCO (R = Y, Tm) and Fe-doped Bi2212 single crystals are discussed. The
comparison of electrical transport properties of the cuprates and quasi-one
dimensional (1D) (TMTSF)2PF6 organic conductor suggests that RBCO and Bi2212
exhibit 1D transport properties, and the step rise at low temperatures in the
resistivities of the cuprates and quasi-1D organic conductor is due to
charge-density-wave ordering. We discuss also phonon-electron interactions in
cuprates at low temperatures.Comment: 10 pages including 4 figure
Re-entrant magnetic field induced charge and spin gaps in the coupled dual-chain quasi-one dimensional organic conductor Perylene[Pt(mnt)]
An inductive method is used to follow the magnetic field-dependent
susceptibility of the coupled charge density wave (CDW) and spin-Peierls (SP)
ordered state behavior in the dual chain organic conductor
Perylene[Pt(mnt)]. In addition to the coexisting SP-CDW state phase
below 8 K and 20 T, the measurements show that a second spin-gapped phase
appears above 20 T that coincides with a field-induced insulating phase. The
results support a strong coupling of the CDW and SP order parameters even in
high magnetic fields, and provide new insight into the nature of the magnetic
susceptibility of dual-chain spin and charge systems.Comment: 6 pages, 6 figure
Superconductivity and Antiferromagnetism in Quasi-one-dimensional Organic Conductors
We review the current understanding of superconductivity in the
quasi-one-dimensional organic conductors of the Bechgaard and Fabre salt
families. We discuss the interplay between superconductivity,
antiferromagnetism, and charge-density-wave fluctuations. The connection to
recent experimental observations supporting unconventional pairing and the
possibility of a triplet-spin order parameter for the superconducting phase is
also presented.Comment: (v1) 30 pages, 13 figures; Review article for the 20th anniversary of
high-Tc superconductivity, to appear in J. Low Temp. Phys. (v2) 1 Ref. adde
Variational description of the dimensional cross-over in the array of coupled one-dimensional conductors
Variational wave function is proposed to describe electronic properties of an
array of one-dimensional conductors coupled by transverse hopping and
interaction. For weak or intermediate in-chain interaction the wave function
has the following structure: Tomonaga-Luttinger bosons with momentum higher
then some variational quantity \tilde\Lambda are in their ground state while
other bosons (with |k|<\tilde\Lambda) form kinks -- fermion-like excitations of
the Tomonaga-Luttinger boson field. Nature of the ground state for this
quasiparticles can be determined by solving three dimensional effective
hamiltonian. Since the anisotropy of the effective hamiltonian is small the use
of the mean field theory is justified. For repulsive interaction possible
phases are density wave and p-wave superconductivity. Our method allows us to
calculate the low-energy part of different electronic Green's functions. In
order to do that it is enough to apply standard perturbation theory technique
to the effective hamiltonian. When the in-chain interaction is strong
\tilde\Lambda vanishes and no fermionic excitation is present in the system. In
this regime the dynamics is described by transversally coupled
Tomonaga-Luttinger bosons
Ising transition in a one-dimensional quarter-filled electron system with dimerization
We examine critical properties of the quarter-filled one-dimensional Hubbard
model with dimerization and with the onsite and nearest-neighbor Coulomb
repulsion U and V. By utilizing the bosonization method, it is shown that the
system exhibits an Ising quantum phase transition from the Mott insulating
state to the charge-ordered insulating state. It is also shown that the
dielectric permittivity exhibits a strong enhancement as decreasing temperature
with power-law dependence at the Ising critical point.Comment: 8 pages, 1 figure, uses elsart.cls, Proc. Int. Symp. ISSP-Kashiwa
2001, submitted to J. Phys. Chem. Solid
Diamagnetism of doped two-leg ladders and probing the nature of their commensurate phases
We study the magnetic orbital effect of a doped two-leg ladder in the
presence of a magnetic field component perpendicular to the ladder plane.
Combining both low-energy approach (bosonization) and numerical simulations
(density-matrix renormalization group) on the strong coupling limit (t-J
model), a rich phase diagram is established as a function of hole doping and
magnetic flux. Above a critical flux, the spin gap is destroyed and a Luttinger
liquid phase is stabilized. Above a second critical flux, a reentrance of the
spin gap at high magnetic flux is found. Interestingly, the phase transitions
are associated with a change of sign of the orbital susceptibility. Focusing on
the small magnetic field regime, the spin-gapped superconducting phase is
robust but immediately acquires algebraic transverse (i.e. along rungs) current
correlations which are commensurate with the 4k_F density correlations. In
addition, we have computed the zero-field orbital susceptibility for a large
range of doping and interactions ratio J/t : we found strong anomalies at low
J/t only in the vicinity of the commensurate fillings corresponding to delta =
1/4 and 1/2. Furthermore, the behavior of the orbital susceptibility reveals
that the nature of these insulating phases is different: while for delta = 1/4
a 4k_F charge density wave is confirmed, the delta = 1/2 phase is shown to be a
bond order wave.Comment: 15 pages, 17 figure
Crossover from two- to three-dimensional critical behavior for nearly antiferromagnetic itinerant electrons
The crossover from two- to three-dimensional critical behavior of nearly
antiferromagnetic itinerant electrons is studied in a regime where the
inter-plane single-particle motion of electrons is quantum-mechanically
incoherent because of thermal fluctuations. This is a relevant regime for very
anisotropic materials like the cuprates. The problem is studied within the
Two-Particle Self-Consistent approach (TPSC), that has been previously shown to
give a quantitative description of Monte Carlo data for the Hubbard model. It
is shown that TPSC belongs to the limit of the universality class. However, contrary to the usual approaches,
cutoffs appear naturally in the microscopic TPSC theory so that parameter-free
calculations can be done for Hubbard models with arbitrary band structure. A
general discussion of universality in the renormalized-classical crossover from
to is also given.Comment: Revtex, 23 pages + 6 postcript figures (with epsfile
- …