Biomedical subjects

C Gazza

Publications and source records attributed to C Gazza.

3 recordsLinked to original sources

PubMed2006

Magnetization plateaus induced by a coupling to the lattice.

We present a novel mechanism for the appearance of magnetization plateaus in quasi-one-dimensional quantum spin systems, which is induced by the coupling to the underlying lattice. We investigate in detail a simple model of a frustrated spin-1/2 Heisenberg chain coupled to adiabatic phonons under an external magnetic field, but the present mechanism is expected to be more general. Using field theoretic methods complemented by extensive density matrix renormalization group techniques, we show that magnetization plateaus at nontrivial rational values of the magnetization can be stabilized by the lattice coupling. We suggest that such a scenario could be relevant for some low dimensional frustrated spin-Peierls compounds.

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PubMed2002

Superconductivity in the two-dimensional t-J model.

Using computational techniques, it is shown that pairing is a robust property of hole-doped antiferromagnetic insulators. In one dimension and for two-leg ladder systems, a BCS-like variational wave function with long-bond spin singlets and a Jastrow factor provides an accurate representation of the ground state of the t-J model, even though strong quantum fluctuations destroy the off-diagonal superconducting long-range order in this case. However, in two dimensions it is argued-and numerically confirmed using several techniques, especially quantum Monte Carlo-that quantum fluctuations are not strong enough to suppress superconductivity.

Journal Article↗

PubMed2000

Doped stripes in models for the cuprates emerging from the one-hole properties of the insulator.

The extended and standard t-J models are computationally studied on ladders and planes, with emphasis on the small J/t region. At couplings compatible with photoemission results for undoped cuprates, half-doped stripes separating pi-shifted antiferromagnetic (AF) domains are found, as in Tranquada's interpretation of neutron experiments. Our main result is that the elementary stripe "building block" resembles the properties of one hole at small J/t, with robust AF correlations across the hole induced by the local tendency of the charge to separate from the spin. This suggests that the seed of half-doped stripes already exists in the unusual properties of the insulating parent compound.

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