Search PubMed⌕ Search

Biomedical subjects

T Giamarchi

Publications and source records attributed to T Giamarchi.

At least 19 recordsLinked to original sources
PubMed2006

Breakup of the Fermi surface near the mott transition in low-dimensional systems.

We investigate the Mott transition in weakly coupled one-dimensional (1D) fermionic chains. Using a generalization of dynamical mean field theory, we show that the Mott gap is suppressed at some critical hopping t{ perpendicular}{c2}. The transition from the 1D insulator to a 2D metal proceeds through an intermediate phase where the Fermi surface is broken into electron and hole pockets. The quasiparticle spectral weight is strongly anisotropic along the Fermi surface, both in the intermediate and metallic phases. We argue that such pockets would look like "arcs" in photoemission experiments.

Journal Article↗
PubMed2006

Spectroscopy of ultracold atoms by periodic lattice modulations.

We present a nonperturbative analysis of a new experimental technique for probing ultracold bosons in an optical lattice by periodic lattice depth modulations. This is done using the time-dependent density-matrix renormalization group method. We find that sharp energy absorption peaks are not unique to the Mott insulating phase at commensurate filling but also exist for superfluids at incommensurate filling. For strong interactions, the peak structure provides an experimental measure of the interaction strength. Moreover, the peak height of the peaks at Planck's omega > or approximately 2U can be employed as a measure of the incommensurability of the system.

Journal Article↗
PubMed2005

Two-component Fermi gas on internal-state-dependent optical lattices.

We study the phase diagram of a one-dimensional, two-component (i.e., pseudo-"spin"-(1/2)) ultracold atomic Fermi gas. The two atom species can have different hopping or mass. A very rich phase diagram for equal densities of the species is found, containing Mott insulators and superfluids. We also discuss coupling such 1D systems and the experimental signatures of the phases. In particular, we compute the spin-structure factor at small momentum, which should reveal a spin gap.

Journal Article↗
PubMed2005

Domain wall roughness in epitaxial ferroelectric PbZr0.2Ti0.8O3 thin films.

The static configuration of ferroelectric domain walls was investigated using atomic force microscopy on epitaxial PbZr(0.2)Ti(0.8)O(3) thin films. Measurements of domain wall roughness reveal a power-law growth of the correlation function of relative displacements B(L) alpha L(2zeta) with zeta approximately 0.26 at short length scales L, followed by an apparent saturation at large L. In the same films, the dynamic exponent mu was found to be approximately 0.6 from independent measurements of domain wall creep. These results give an effective domain wall dimensionality of d = 2.5, in good agreement with theoretical calculations for a two-dimensional elastic interface in the presence of random-bond disorder and long-range dipolar interactions.

Journal Article↗
PubMed2004

Deconfinement in a 2D optical lattice of coupled 1D boson systems.

We show that a two-dimensional (2D) array of 1D interacting boson tubes has a deconfinement transition between a 1D Mott insulator and a 3D superfluid for commensurate fillings and a dimensional crossover for the incommensurate case. We determine the phase diagram and excitations of this system and discuss the consequences for Bose condensates loaded in 2D optical lattices.

Journal Article↗
PubMed2004

Point-contact tunneling involving low-dimensional spin-triplet superconductors.

We modify and extend previous microscopic calculations of tunneling in superconducting junctions based on a nonequilibrium Green function formalism to include the case of spin-triplet pairing. We show that distinctive features are present in the I-V characteristics of different kinds of junctions, in particular, when the effects of magnetic fields are taken into account, that permit to identify the type of pairing. We discuss the relevance of these results in the context of quasi-one-dimensional organic superconductors such as (TMTSF)2PF6 and layered compounds like Sr2RuO(4).

Journal Article↗
PubMed2003

Numerical simulation evidence of dynamical transverse meissner effect and moving bose glass phase.

We present 3D numerical simulation results of moving vortex lattices in the presence of 1D correlated disorder at zero temperature. Our results with field tilting confirm the theoretical predictions of a moving Bose glass phase, characterized by transverse pinning and dynamical transverse Meissner effect, the moving flux lines being localized along the correlated disorder direction. Beyond a critical transverse field, vortex lines exhibit along all their length a "kink" structure resulting from an effective static "tin roof" pinning potential in the transverse direction.

Journal Article↗
PubMed2002

Domain wall creep in epitaxial ferroelectric Pb(Zr(0.2)Ti(0.08)O(3) thin films.

Ferroelectric switching and nanoscale domain dynamics were investigated using atomic force microscopy on monocrystalline Pb(Zr(0.2)Ti(0.8))O(3) thin films. Measurements of domain size versus writing time reveal a two-step domain growth mechanism, in which initial nucleation is followed by radial domain wall motion perpendicular to the polarization direction. The electric field dependence of the domain wall velocity demonstrates that domain wall motion in ferroelectric thin films is a creep process, with the critical exponent mu close to 1. The dimensionality of the films suggests that disorder is at the origin of the observed creep behavior.

Journal Article↗
PubMed2001

Deconfinement transition and Luttinger to Fermi liquid crossover in quasi-one-dimensional systems.

We investigate a system of one-dimensional Hubbard chains of interacting fermions coupled by interchain hopping. Using a generalization of the dynamical mean-field theory we study the deconfinement transition from a Mott insulator to a metal and the crossover between Luttinger and Fermi liquid phases. One-particle properties, local spin response, and interchain optical conductivity are calculated. Possible applications to organic conductors are discussed.

Journal Article↗
PubMed2001

A Bragg glass phase in the vortex lattice of a type II superconductor.

Although crystals are usually quite stable, they are sensitive to a disordered environment: even an infinitesimal amount of impurities can lead to the destruction of crystalline order. The resulting state of matter has been a long-standing puzzle. Until recently it was believed to be an amorphous state in which the crystal would break into 'crystallites'. But a different theory predicts the existence of a novel phase of matter: the so-called Bragg glass, which is a glass and yet nearly as ordered as a perfect crystal. The 'lattice' of vortices that contain magnetic flux in type II superconductors provide a good system to investigate these ideas. Here we show that neutron-diffraction data of the vortex lattice provides unambiguous evidence for a weak, power-law decay of the crystalline order characteristic of a Bragg glass. The theory also predicts accurately the electrical transport properties of superconductors; it naturally explains the observed phase transitions and the dramatic jumps in the critical current associated with the melting of the Bragg glass. Moreover, the model explains experiments as diverse as X-ray scattering in disordered liquid crystals and the conductivity of electronic crystals.

Journal Article↗