1,452 research outputs found
Antiferromagnetic integer-spin chains in a staggered magnetic field: approaching the thermodynamic limit through the infinite-size DMRG
We investigate the behavior of antiferromagnetic integer-spin chains in a
staggered magnetic field, by means of the density-matrix renormalization group,
carefully addressing the role of finite-size effects within the Haldane phase
at small fields. In the case of spin S=2, we determine the dependence of the
groundstate energy and magnetization on the external field, in the
thermodynamic limit, and show how the peculiar finite-size behavior can be
connected with the crossover in the groundstate from a spin liquid to a
polarized N\'eel state.Comment: 7 pages, 5 figure
Spectroscopic evidences of quantum critical charge fluctuations in cuprates
We calculate the optical conductivity in a clean system of quasiparticles
coupled to charge-ordering collective modes. The absorption induced by these
modes may produce an anomalous frequency and temperature dependence of
low-energy optical absorption in some cuprates. However, the coupling with
lattice degrees of freedom introduces a non-universal energy scale leading to
scaling violation in low-temperature optical conductivity.Comment: Proceedings of M2S 2006. To appear in Physica
Intrinsic instability of electronic interfaces with strong Rashba coupling
We consider a model for the two-dimensional electron gas formed at the
interface of oxide heterostructures, which includes a Rashba spin-orbit
coupling proportional to the electric field perpendicular to the interface.
Based on the standard mechanism of polarity catastrophe, we assume that the
electric field is proportional to the electron density. Under these simple and
general assumptions, we show that a phase separation instability occurs for
realistic values of the spin-orbit coupling and of the band parameters. This
could provide an intrinsic mechanism for the recently observed inhomogeneous
phases at the LaAlO_3/SrTiO_3 or LaTiO_3/SrTiO_3 interfaces.Comment: 5 pages, 4 figure
Collective transport and optical absorption near the stripe criticality
Within the stripe quantum critical point scenario for high
superconductors, we point out the possible direct contribution of charge
collective fluctuations to the optical absorption and to the d.c. resistivity.Comment: 2 pages 2 figures 1 style fil
Single-particle spectra near a stripe instability
We analyze the single-particle spectra of a bi-layered electron system near a
stripe instability and compare the results with ARPES experiments on the Bi2212
cuprate superconductor near optimum doping, addressing also the issue of the
puzzling absence of bonding-antibonding splitting.Comment: Proceedings of the XXII International Conference on Low Temperature
Physics August 4-11, 1999, Espoo and Helsinki, Finland (minor changes to the
figure) Similar results in the Proceedings of the International Workshop on
``Electronic crystals, ECRYS-99'', May 31-June 5 1999, La Colle sur Loup
(France), J. Phys. IV France 9, Pr10-337 (1999
The physics of the stripe quantum critical point in the superconducting cuprates
We elaborate on several observable consequences of the Quantum-Critical-Point
scenario. In particular we show that the strong k-dependent scattering of the
quasiparticles with the quasi-critical charge and spin fluctuations reproduces
the main features of the low-energy spectral weights and of the observed Fermi
surfaces. In the underdoped cuprates the attractive k-dependent charge
scattering drives the formation of the pseudogap at the M points below the
crossover temperature T^*. In this context we discuss models for pseudogap
formation with relevant scattering in the particle-particle and particle-hole
channels. The experimental consequences for the pair-fluctuation and for the
pseudogap behavior are investigated.Comment: 4 pages, 2 enclosed figures, Proceedings of M2S-HTS
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