320 research outputs found
Characterization of the Torsional Piezoelectric-like Response of Tantalum Trisulfide Associated with Charge-Density-Wave Depinning
We have studied the frequency and voltage dependence of voltage-induced
torsional strains in orthorhombic TaS3 [V. Ya. Pokrovskii, et al, Phys. Rev.
Lett. 98, 206404 (2007)] by measuring the modulation of the resonant frequency
of an RF cavity containing the sample. The strain has an onset voltage below
the charge-density-wave (CDW) threshold voltages associated with changes in
shear compliance and resistance, suggesting that the strain is associated with
polarization of the CDW rather than CDW current. Measurements with square-wave
voltages show that the strain is very sluggish, not even reaching its dc value
at a frequency of 0.1 Hz, but the dynamics appear to be very sample dependent.
By applying oscillating torque while biasing the sample with a dc current, we
have also looked for strain induced voltage in the sample; none is observed at
the low biases where the voltage-induced strains first occur, but an induced
voltage is observed at higher biases, probably associated with strain-dependent
CDW conductance.Comment: 11 pages, including 3 figures, to be published in Phys. Rev. B (Rapid
Comm.
Interlayer tunneling spectroscopy of graphite at high magnetic field oriented parallel to the layers
Interlayer tunneling in graphite mesa-type structures is studied at a strong
in-plane magnetic field up to 55 T and low temperature K. The
tunneling spectrum vs. has a pronounced peak at a finite voltage
. The peak position increases linearly with . To explain the
experiment, we develop a theoretical model of graphite in the crossed electric
and magnetic fields. When the fields satisfy the resonant condition
, where is the velocity of the two-dimensional Dirac electrons in
graphene, the wave functions delocalize and give rise to the peak in the
tunneling spectrum observed in the experiment.Comment: 6 pages, 6 figures; corresponds to the published version in Eur.
Phys. J. Special Topics, Proceedings of the IMPACT conference 2012,
http://lptms.u-psud.fr/impact2012
Subsurface microstructural changes in a cast heat resisting alloy caused by high temperature corrosion
A cast HP ModNb alloy (Fe–25Cr–35Ni–1Nb, wt.%) was oxidised and carburised in CO–CO2 corresponding to aC = 0.1 and pO2 = 3 1016 atm at 1080 C. Formation of an external, chromium-rich oxide scale led to depletion of this metal in a deep alloy subsurface zone. Within that zone, secondary chromium-rich carbides dissolved, primary carbides oxidised, solute silicon and aluminium internally oxidised, and extensive porosity developed. Pore volumes correspond to the difference between metal loss by scaling and metal displacement by internal oxidation, assuming the scale–metal interface to be fixed. The pores are concluded to be Kirkendall void
Alternativni modeli za složeno opuštanje niskoenergijskih pobuđenja u sustavima s valovima gustoće
We apply the Palmer, Stein, Abrahams and Anderson (PSAA) model of hierarchically constrained dynamics for glassy relaxation to the complex thermal relaxation at very low temperatures in density wave systems. Alternatively, we simulate various experimental conditions in a simple, intuitive model of an electrical RC line and find some relations with the PSAA parameters.Primjenjujemo model Palmera, Steina, Abrahamsa i Andersona (PSAA) za hijerarhijski zapriječenu dinamiku opuštanja u staklima na kompleksno opuštanje topline na vrlo niskim temperaturama u sistemima s valovima gustoće. Jednako tako, pomoću jednostavnog modela slijeda električnih RC (otpor – kapacitet) krugova oponašamo različite eksperimentalne uvjete i nalazimo neke odnose s dobivenim PSAA parametrima
Finite dimensional quantizations of the (q,p) plane : new space and momentum inequalities
We present a N-dimensional quantization a la Berezin-Klauder or frame
quantization of the complex plane based on overcomplete families of states
(coherent states) generated by the N first harmonic oscillator eigenstates. The
spectra of position and momentum operators are finite and eigenvalues are
equal, up to a factor, to the zeros of Hermite polynomials. From numerical and
theoretical studies of the large behavior of the product of non null smallest positive and largest eigenvalues, we infer
the inequality (resp. ) involving, in suitable
units, the minimal () and maximal () sizes of
regions of space (resp. momentum) which are accessible to exploration within
this finite-dimensional quantum framework. Interesting issues on the
measurement process and connections with the finite Chern-Simons matrix model
for the Quantum Hall effect are discussed
Anomalous asymmetry of magnetoresistance in NbSe single crystals
A pronounced asymmetry of magnetoresistance with respect to the magnetic
field direction is observed for NbSe crystals placed in a magnetic field
perpendicular to their conducting planes. It is shown that the effect persists
in a wide temperature range and manifests itself starting from a certain
magnetic induction value , which at K corresponds to the
transition to the quantum limit, i.to the state where the Landay level
splitting exceeds the temperature.Comment: 4 pages, 6 figures, to be appeared in JETP Let
Alternativni modeli za složeno opuštanje niskoenergijskih pobuđenja u sustavima s valovima gustoće
We apply the Palmer, Stein, Abrahams and Anderson (PSAA) model of hierarchically constrained dynamics for glassy relaxation to the complex thermal relaxation at very low temperatures in density wave systems. Alternatively, we simulate various experimental conditions in a simple, intuitive model of an electrical RC line and find some relations with the PSAA parameters.Primjenjujemo model Palmera, Steina, Abrahamsa i Andersona (PSAA) za hijerarhijski zapriječenu dinamiku opuštanja u staklima na kompleksno opuštanje topline na vrlo niskim temperaturama u sistemima s valovima gustoće. Jednako tako, pomoću jednostavnog modela slijeda električnih RC (otpor – kapacitet) krugova oponašamo različite eksperimentalne uvjete i nalazimo neke odnose s dobivenim PSAA parametrima
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