7,204 research outputs found
Spiral phases and two-particle bound states from a systematic low-energy effective theory for magnons, electrons, and holes in an antiferromagnet
We have constructed a systematic low-energy effective theory for hole- and
electron-doped antiferromagnets, where holes reside in momentum space pockets
centered at and where electrons live in
pockets centered at or . The effective
theory is used to investigate the magnon-mediated binding between two holes or
two electrons in an otherwise undoped system. We derive the one-magnon exchange
potential from the effective theory and then solve the corresponding
two-quasiparticle Schr\"odinger equation. As a result, we find bound state wave
functions that resemble -like or -like symmetry. We also
study possible ground states of lightly doped antiferromagnets.Comment: 2 Pages; Proc. of SCES'07, Housto
Ionization signals from electrons and alpha-particles in mixtures of liquid Argon and Nitrogen - perspectives on protons for Gamma Resonant Nuclear Absorption applications
In this paper we report on a detailed study of ionization signals produced by
Compton electrons and alpha-particles in a Time Projection Chamber (TPC) flled
with different mixtures of liquid Argon and Nitrogen. The measurements were
carried out with Nitrogen concentrations up to 15% and a drift electric feld in
the range 0-50 kV/cm. A prediction for proton ionization signals is made by
means of interpolation. This study has been conducted in view of the possible
use of liquid Ar-N2 TPCs for the detection of gamma-rays in the resonant band
of the Nitrogen absorption spectrum, a promising technology for security and
medical applications
30 kV coaxial vacuum-tight feedthrough for operation at cryogenic temperatures
In this paper we describe the technology of building a vacuum-tight high
voltage feedthrough which is able to operate at voltages up to 30 kV. The
feedthrough has a coaxial structure with a grounded sheath which makes it
capable to lead high voltage potentials into cryogenic liquids, without risk of
surface discharges in the gas phase above the liquid level. The feedthrough is
designed to be used in ionization detectors, based on liquefied noble gases,
such as Argon or Xenon
- âŠ