26 research outputs found
Coherent back-scattering near the two-dimensional metal-insulator transition
We have studied corrections to conductivity due to the coherent
backscattering in low-disordered two-dimensional electron systems in silicon
for a range of electron densities including the vicinity of the metal-insulator
transition, where the dramatic increase of the spin susceptibility has been
observed earlier. We show that the corrections, which exist deeper in the
metallic phase, weaken upon approaching to the transition and practically
vanish at the critical density, thus suggesting that the localization is
suppressed near and at the transition even in zero field.Comment: to appear in PR
Flow diagram of the metal-insulator transition in two dimensions
The discovery of the metal-insulator transition (MIT) in two-dimensional (2D)
electron systems challenged the veracity of one of the most influential
conjectures in the physics of disordered electrons, which states that `in two
dimensions, there is no true metallic behaviour'; no matter how weak the
disorder, electrons would be trapped and unable to conduct a current. However,
that theory did not account for interactions between the electrons. Here we
investigate the interplay between the electron-electron interactions and
disorder near the MIT using simultaneous measurements of electrical resistivity
and magnetoconductance. We show that both the resistance and interaction
amplitude exhibit a fan-like spread as the MIT is crossed. From these data we
construct a resistance-interaction flow diagram of the MIT that clearly reveals
a quantum critical point, as predicted by the two-parameter scaling theory
(Punnoose and Finkel'stein, Science 310, 289 (2005)). The metallic side of this
diagram is accurately described by the renormalization group theory without any
fitting parameters. In particular, the metallic temperature dependence of the
resistance sets in when the interaction amplitude reaches gamma_2 = 0.45 - a
value in remarkable agreement with the one predicted by the theory.Comment: as publishe
Spin-independent origin of the strongly enhanced effective mass in a dilute 2D electron system
We have accurately measured the effective mass in a dilute two-dimensional
electron system in silicon by analyzing temperature dependence of the
Shubnikov-de Haas oscillations in the low-temperature limit. A sharp increase
of the effective mass with decreasing electron density has been observed. Using
tilted magnetic fields, we have found that the enhanced effective mass is
independent of the degree of spin polarization, which points to a
spin-independent origin of the mass enhancement and is in contradiction with
existing theories
Pauli spin susceptibility of a strongly correlated two-dimensional electron liquid
Thermodynamic measurements reveal that the Pauli spin susceptibility of
strongly correlated two-dimensional electrons in silicon grows critically at
low electron densities - behavior that is characteristic of the existence of a
phase transition.Comment: As publishe
New chromogenic dipeptide substrate for continuous assay of the d-alanyl-d-alanine dipeptidase VanX required for high-level vancomycin resistance
International audienc
Temperature dependence of low-energy phonons in magnetic nonsuperconducting TbNi<sub>2</sub>B<sub>2</sub>C
We report temperature dependence of low-energy phonons in magnetic
nonsuperconducting TbNi2B2C single crystals measured by inelastic neutron
scattering. We observed a low-temperature softening and broadening of two
phonon branches, qualitatively similar to that previously reported for
superconducting RNi2B2C (R= rare earth, Y) compounds. This result suggests that
the superconductivity in TbNi2B2C compounds is absent not because of a weak
electron-phonon coupling but as a result of pairbreaking due to magnetism