Biomedical subjects

L Brey

Publications and source records attributed to L Brey.

At least 19 recordsLinked to original sources

PubMed2006

Luttinger liquid at the edge of undoped graphene in a strong magnetic field.

We demonstrate that an undoped two-dimensional carbon plane (graphene) whose bulk is in the integer quantum Hall regime supports a nonchiral Luttinger liquid at an armchair edge. This behavior arises due to the unusual dispersion of the noninteracting edge states, causing a crossing of bands with different valley and spin indices at the edge. We demonstrate that this stabilizes a domain wall structure with a spontaneously ordered phase degree of freedom. This coherent domain wall supports gapless charged excitations, and has a power law tunneling I-V with a nonintegral exponent. In proximity to a bulk lead, the edge may undergo a quantum phase transition between the Luttinger liquid phase and a metallic state.

Journal Article↗

PubMed2004

Ferromagnetism mediated by few electrons in a semimagnetic quantum dot.

A (II,Mn)VI diluted magnetic semiconductor quantum dot with an integer number of electrons controlled with a gate voltage is considered. We show that a single electron is able to induce a collective spontaneous magnetization of the Mn spins, overcoming the short range antiferromagnetic interactions, at a temperature order of 1 K, 2 orders of magnitude above the ordering temperature in bulk. The magnetic behavior of the dot depends dramatically on the parity of the number of electrons in the dot.

Journal Article↗

PubMed2002

Lattice-spin mechanism in colossal magnetoresistive manganites.

We present a single-orbital double-exchange model, coupled with cooperative phonons (the so called breathing modes of the oxygen octahedra in manganites). The model is studied with Monte Carlo simulations. For a finite range of doping and coupling constants, a first-order metal-insulator phase transition is found, which coincides with the paramagnetic-ferromagnetic phase transition. The insulating state is due to the self-trapping of every carrier within an oxygen octahedron distortion.

Journal Article↗

PubMed2000

Phase diagram of diluted magnetic semiconductor quantum wells

The phase diagram of diluted magnetic semiconductor quantum wells is investigated. The interaction between the carriers in the hole gas can lead to first-order ferromagnetic transitions, which remain abrupt in applied fields. These transitions can be induced by magnetic fields or, in double-layer systems, by electric fields. We make a number of precise experimental predictions for observing these first-order phase transitions.

Journal Article↗

PubMed1996