652 research outputs found
Substitution Effect by Deuterated Donors on Superconductivity in -(BEDT-TTF)Cu[N(CN)]Br
We investigate the superconductivity in the deuterated BEDT-TTF molecular
substitution system
-[(h8-BEDT-TTF)(d8-BEDT-TTF)]Cu[N(CN)]Br, where h8
and d8 denote fully hydrogenated and deuterated molecules, respectively.
Systematic and wide range ( = 0 -- 1) substitution can control chemical
pressure finely near the Mott boundary, which results in the modification of
the superconductivity. After cooling slowly, the increase of
observed up to 0.1 is evidently caused by the chemical pressure
effect. Neither reduction of nor suppression of
superconducting volume fraction is found below 0.5. This demonstrates
that the effect of disorder by substitution is negligible in the present
system. With further increase of , both and superconducting
volume fraction start to decrease toward the values in = 1.Comment: J. Phys. Soc. Jp
Debye relaxation in high magnetic fields
Dielectric relaxation is universal in characterizing polar liquids and
solids, insulators, and semiconductors, and the theoretical models are well
developed. However, in high magnetic fields, previously unknown aspects of
dielectric relaxation can be revealed and exploited. Here, we report low
temperature dielectric relaxation measurements in lightly doped silicon in high
dc magnetic fields B both parallel and perpendicular to the applied ac electric
field E. For B//E, we observe a temperature and magnetic field dependent
dielectric dispersion e(w)characteristic of conventional Debye relaxation where
the free carrier concentration is dependent on thermal dopant ionization,
magnetic freeze-out, and/or magnetic localization effects. However, for BperpE,
anomalous dispersion emerges in e(w) with increasing magnetic field. It is
shown that the Debye formalism can be simply extended by adding the Lorentz
force to describe the general response of a dielectric in crossed magnetic and
electric fields. Moreover, we predict and observe a new transverse dielectric
response EH perp B perp E not previously described in magneto-dielectric
measurements. The new formalism allows the determination of the mobility and
the ability to discriminate between magnetic localization/freeze out and
Lorentz force effects in the magneto-dielectric response.Comment: 19 pages, 6 figure
A bulk 2D Pauli Limited Superconductor
We present a nearly perfect Pauli-limited critical field phase diagram for
the anisotropic organic superconductor \-(ET)NH(SCN) when
the applied magnetic field is oriented parallel to the conducting layers. The
critical fields ({H_{c_2}) were found by use of penetration depth
measurements. Because {H_{c_2} is Pauli-limited, the size of the
superconducting energy gap can be calculated. The role of spin-orbit scattering
and many-body effects play a role in explaining our measurements.Comment: 4 pages, 5 figures. V5, corrections were made to the text, present
data was include
Superconductivity in an organic insulator at very high magnetic fields
We investigate by electrical transport the field-induced superconducting
state (FISC) in the organic conductor -(BETS)FeCl. Below 4 K,
antiferromagnetic-insulator, metallic, and eventually superconducting (FISC)
ground states are observed with increasing in-plane magnetic field. The FISC
state survives between 18 and 41 T, and can be interpreted in terms of the
Jaccarino-Peter effect, where the external magnetic field {\em compensates} the
exchange field of aligned Fe ions. We further argue that the Fe
moments are essential to stabilize the resulting singlet, two-dimensional
superconducting stateComment: 9 pages 3 figure
Critical State Behaviour in a Low Dimensional Metal Induced by Strong Magnetic Fields
We present the results of magnetotransport and magnetic torque measurements
on the alpha-(BEDT-TTF)2KHg(SCN)4 charge-transfer salt within the high magnetic
field phase, in magnetic fields extending to 33 T and temperatures as low as 27
mK. While the high magnetic field phase (at fields greater than ~ 23 T) is
expected, on theoretical grounds, to be either a modulated charge-density wave
phase or a charge/spin-density wave hybrid, the resistivity undergoes a
dramatic drop below ~ 3 K within the high magnetic field phase, falling in an
approximately exponential fashion at low temperatures, while the magnetic
torque exhibits pronounced hysteresis effects. This hysteresis, which occurs
over a broad range of fields, is both strongly temperature-dependent and has
several of the behavioural characteristics predicted by critical-state models
used to describe the pinning of vortices in type II superconductors in strong
magnetic fields. Thus, rather than exhibiting the usual behaviour expected for
a density wave ground state, both the transport and the magnetic properties of
alpha-(BEDT-TTF)2KHg(SCN)4, at high magnetic fields, closely resembles those of
a type II superconductor
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