16 research outputs found
Anomalous Electron Transport in Field-Effect Transistors with Titanium Ditelluride Semimetal Thin-Film Channels
We report on "graphene-like" mechanical exfoliation of thin films of titanium
ditelluride and investigation of their electronic properties. The exfoliated
crystalline TiTe2 films were used as the channel layers in the back-gated
field-effect transistors fabricated with Ti/Al/Au metal contacts on SiO2/Si
substrates. The room-temperature current-voltage characteristics revealed
strongly non-linear behavior with signatures of the source-drain threshold
voltage similar to those observed in the charge-density-wave devices. The
drain-current showed an unusual non-monotonic dependence on the gate bias
characterized by the presence of multiple peaks. The obtained results can be
potentially used for implementation of the non-Boolean logic gates.Comment: 11 pages, 4 figure
Competing phases in the high field phase diagram of (TMTSF)ClO
A model is presented for the high field phase diagram of (TMTSF)ClO,
taking into account the anion ordering, which splits the Fermi surface in two
bands. For strong enough field, the largest metal-SDW critical temperature
corresponds to the N=0 phase, which originates from two intraband nesting
processes. At lower temperature, the competition between these processes puts
at disadvantage the N=0 phase vs. the N=1 phase, which is due to interband
nesting. A first order transition takes then place from the N=0 to N=1 phase.
We ascribe to this effect the experimentally observed phase diagrams.Comment: 5 pages, 3 figures (to appear in Phys. Rev. Lett.
NMR imaging of the soliton lattice profile in the spin-Peierls compound CuGeO_3
In the spin-Peierls compound CuGeO, the commensurate-incommensurate
transition concerning the modulation of atomic position and the local
spin-polarization is fully monitored at T=0 by the application of an external
magnetic field () above a threshold value 13 Tesla. The
solitonic profile of the spin-polarization, as well as its absolute magnitude,
has been precisely imaged from NMR lineshapes obtained for
varying from 0.0015 to 2. This offers a unique possibility
to test quantitatively the various numerical and analytical methods developed
to solve a generic Hamiltonian in 1-D physics, namely strongly interacting
fermions in presence of electron-phonon coupling at arbitrary band filling.Comment: 3 pages, 4 eps figures, RevTeX, submitted to Physical Review Lette
Coexistence or Separation of the Superconducting, Antiferromagnetic, and Paramagnetic Phases in Quasi One-Dimensional (TMTSF)2PF6 ?
We report on experimental studies of the character of phase transitions in
the quasi-1D organic compound (TMTSF)2PF6 in the close vicinity of the borders
between the paramagnetic metal PM, antiferromagnetic insulator AF, and
superconducting SC states. In order to drive the system through the phase
border P_0(T_0), the sample was maintained at fixed temperature T and pressure
P, whereas the critical pressure P_0 was tuned by applying the magnetic field
B. In this approach, the magnetic field was used (i) for tuning (P-P_0), and
(ii) for identifying the phase composition (due to qualitatively different
magnetoresistance behavior in different phases). Experimentally, we measured
R(B) and its temperature dependence R(B,T) in the pressure range (0 - 1)GPa.
Our studies focus on the features of the magnetoresistance at the phase
transition between the PM and AF phases, in the close vicinity to the
superconducting transition at T~1K. We found pronounced history effects arising
when the AF/PM phase border is crossed by sweeping the magnetic field: the
resistance depends on a trajectory which the system arrives at a given point of
the P-B-T phase space. In the transition from the PM to AF phase, the features
of the PM phase extends well into the AF phase. At the opposite transition from
the AF to PM phase, the features of the AF phase are observed in the PM phase.
These results evidence for a macroscopically inhomogeneous state, which
contains macroscopic inclusions of the minority phase. When the system is
driven away from the transition, the homogeneous state is restored; upon a
return motion to the phase boundary, no signatures of the minority phase are
observed up to the very phase boundary.Comment: 10 figures, 23 page
Effect of nearest- and next-nearest neighbor interactions on the spin-wave velocity of one-dimensional quarter-filled spin-density-wave conductors
We study spin fluctuations in quarter-filled one-dimensional
spin-density-wave systems in presence of short-range Coulomb interactions. By
applying a path integral method, the spin-wave velocity is calculated as a
function of on-site (U), nearest (V) and next-nearest (V_2) neighbor-site
interactions. With increasing V or V_2, the pure spin-density-wave state
evolves into a state with coexisting spin- and charge-density waves. The
spin-wave velocity is reduced when several density waves coexist in the ground
state, and may even vanish at large V. The effect of dimerization along the
chain is also considered.Comment: REVTeX, 11 pages, 9 figure
Mean-field Phase Diagram of Two-Dimensional Electrons with Disorder in a Weak Magnetic Field
We study two-dimensional interacting electrons in a weak perpendicular
magnetic field with the filling factor and in the presence of a
quenched disorder. In the framework of the Hartree-Fock approximation, we
obtain the mean-field phase diagram for the partially filled highest Landau
level. We find that the CDW state can exist if the Landau level broadening
does not exceed the critical value .
Our analysis of weak crystallization corrections to the mean-field results
shows that these corrections are of the order of and
therefore can be neglected
Extreme Type-II Superconductors in a Magnetic Field: A Theory of Critical Fluctuations
A theory of critical fluctuations in extreme type-II superconductors
subjected to a finite but weak external magnetic field is presented. It is
shown that the standard Ginzburg-Landau representation of this problem can be
recast, with help of a novel mapping, as a theory of a new "superconductor", in
an effective magnetic field whose overall value is zero, consisting of the
original uniform field and a set of neutralizing unit fluxes attached to
fluctuating vortex lines. The long distance behavior is related to
the anisotropic gauge theory in which the original magnetic field plays the
role of "charge". The consequences of this "gauge theory" scenario for the
critical behavior in high temperature superconductors are explored in detail,
with particular emphasis on questions of 3D XY vs. Landau level scaling,
physical nature of the vortex "line liquid" and the true normal state, and
fluctuation thermodynamics and transport. A "minimal" set of requirements for
the theory of vortex-lattice melting in the critical region is also proposed
and discussed.Comment: 28 RevTeX pages, 4 .ps figures; appendix A added, additional
references, streamlined Secs. IV and V in response to referees' comment
Charged domain walls as quantum strings living on a lattice
A generic lattice cut-off model is introduced describing the quantum
meandering of a single cuprate stripe. The fixed point dynamics is derived,
showing besides free string behavior a variety of partially quantum disordered
phases, bearing relationships both with quantum spin-chains and surface
statistical physics.Comment: 22 page, 17 figure