arXiv subjects

F. Zhou

Publications and source records attributed to F. Zhou.

60 records · Page 4Linked to original sources

arXiv1998

Anomalous mesoscopic fluctuations of transport coefficients above the critical temperature

We show that above the critical temperature of superconductor - metal phase transitions, both the longitudinal and Hall conductivity exhibit strong temperature dependent mesoscopic fluctuations, with amplitudes much larger than the mesoscopic fluctuations in noninteracting normal metals. Such an enhancement of the mesoscopic fluctuations arises from pairing correlations and is strongly dependent on dimensions.

cond-mat.mes-hall↗

arXiv1998

Negative superfluid densities in superconducting films in a parallel magnetic field

In this paper we develop a theory of mesoscopic fluctuations in disordered thin superconducting films in a parallel magnetic field. At zero temperature and sufficiently strong magnetic field the system undergoes a phase transition into a state characterized by a superfluid density, which is random in sign. Consequently, in this region, random supercurrents are spontaneously created in the ground state of the system, and it belongs to the same universality class as the two dimensional XY spin glass with a random sign of the exchange interaction.

cond-mat.supr-con↗

arXiv1997

Hall effect in NS and SNS junctions

Hall effect in SN and SNS junctions is considered. It is shown that at small temperature the Hall voltage is significantly suppressed as compared to its normal metal value. The time dependence of the Hall voltage in SNS junctions has a form of narrow pulses with the Josephson frequency.

cond-mat.mes-hall↗

arXiv1997

Magnetic and thermodynamic properties of Sr_{2}LaFe_{3}O_{9}

Using a Dirac-Heisenberg Hamiltonian with biquadratic exchange interactions, we study the effect of iron disproportionation on the magnetic ordering, and describe the first-order magnetic transition occurring in the perovskite Sr_{2}LaFe_{3}O_{9}. Upon fitting the experimental data, we give an estimate of the exchange integrals for the antiferromagntic and ferromagnetic interactions, in agreement with previous works on kindered compounds. Spin-wave theory yields a magnon spectrum with a gapless antiferromagnetic mode together with two gapped ferromagnetic ones.

cond-mat.str-el↗

arXiv1996

Resistance of superconductor-normal metal-superconductor junctions

It is shown that the conductance of a superconductor-normal metal-superconductor junction can exhibit a significant dependence on the phase of the superconducting order parameter in the situation when the size of the normal region of the junction is much larger than the normal metal coherence length and the critical current of the junction is already exponentially small. The period of the conductance oscillations as a function of the phase can be equal to $π$ or $2π$ depending on parameters of the system.

cond-mat↗

arXiv1995

Giant Microwave Absorption in Metallic Grains: Relaxation Mechanism

We show that the low frequency microwave absorption of an ensemble of small metallic grains at low temperatures is dominated by a mesoscopic relaxation mechanism. Giant positive magnetoresistance and very strong temperature dependence of the microwave conductivity is predicted.

cond-mat↗