Adrian Del Maestro

He 4 Luttinger Liquid in Nanopores

We study the low-temperature properties of a 4He fluid confined in nanopores, using large-scale quantum Monte Carlo simulations with realistic He-He and He-pore interactions. In the narrow-pore limit, the system can be described by the quantum hydrodynamic theory known as Luttinger liquid theory with a large Luttinger parameter, corresponding to the dominance of solid tendencies and strong susceptibility to pinning by a periodic or random potential from the pore walls. On the other hand, for wider pores, the central region appears to behave like a Luttinger liquid with a smaller Luttinger parameter, and may be protected from pinning by the wall potential, offering the possibility of experimental detection of a Luttinger liquid.

From stripe to checkerboard ordering of charge-density waves on the square lattice in the presence of quenched disorder

We discuss the effects of quenched disorder on a model of charge density wave (CDW) ordering on the square lattice. Our model may be applicable to the cuprate superconductors, where a random electrostatic potential exists in the CuO2 planes as a result of the presence of charged dopants. We argue that the presence of a random potential can affect the unidirectionality of the CDW order, characterized by an Ising order parameter. Coupling to a unidirectional CDW, the random potential can lead to the formation of domains with 90 degree relative orientation, thus tending to restore the rotational symmetry of the underlying lattice. We find that the correlation length of the Ising order can be significantly larger than the CDW correlation length. For a checkerboard CDW on the other hand, disorder generates spatial anisotropies on short length scales and thus some degree of unidirectionality. We quantify these disorder effects and suggest new techniques for analyzing the local density of states (LDOS) data measured in scanning tunneling microscopy experiments.

Interacting bosons in one dimension and the applicability of Luttinger-liquid theory as revealed by path-integral quantum Monte Carlo calculations

Harmonically trapped ultra-cold atoms and He in nanopores provide new experimental realizations of bosons in one dimension, motivating the search for a more complete theoretical understanding of their low energy properties. Worm algorithm path integral quantum Monte Carlo results for interacting bosons restricted to the one dimensional continuum are compared to the finite temperature and system size predictions of Luttinger liquid theory. For large system sizes at low temperature, excellent agreement is obtained after including the leading irrelevant interactions in the Hamiltonian which are determined explicitly.

Understanding paramagnetic spin correlations in the spin-liquid pyrochlore Tb 2 Ti 2 O 7

Recent elastic and inelastic neutron scattering studies of the highly frustrated pyrochlore antiferromagnet

Infinite Randomness Fixed Point of the Superconductor-Metal Quantum Phase Transition

{\mathrm{Tb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}

Universal thermal and electrical transport near the superconductor-metal quantum phase transition in nanowires

have shown some very intriguing features that cannot be modeled by the local

Absence of superfluidity in a quasi-one-dimensional parahydrogen fluid adsorbed inside carbon nanotubes

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Adsorption by design: Tuning atom-graphene van der Waals interactions via mechanical strain

classical Ising model, naively expected to describe this system at low temperatures. By including single-ion excitations from the ground state doublet to higher crystal field levels, we successfully describe the elastic neutron scattering pattern and dispersion relations in

Dynamical Conductivity at the Dirty Superconductor-Metal Quantum Phase Transition

{\mathrm{Tb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7},

Backscattering Between Helical Edge States via Dynamic Nuclear Polarization

quantitatively consistent with experimental observations.