155 research outputs found
Boundary Green's Function for Spin-Incoherent Interacting Electrons in One Dimension
The spin-incoherent regime of one-dimensional electrons has recently been
explored using the Bethe ansatz and a bosonized path integral approach,
revealing that the spin incoherence dramatically influences the correlations of
charge excitations. We here introduce a bosonization scheme for strongly
interacting electrons, allowing us to generalize the description to account for
the presence of an open boundary. By calculating the single-electron Green's
function we find that the charge sector power-law scaling is highly sensitive
to the boundary. Our result allows for a detailed description of the crossover
between boundary and bulk regimes. We predict that scanning tunneling
microscopy on a spin-incoherent system will pick up oscillations in the
differential tunneling conductance as a function of the applied voltage at
"intermediate" distances from a real or a dynamically generated boundary.
The wavelength of the oscillations, , probes the speed of the
charge excitations, and therefore the strength of the electron-electron
interaction.Comment: REVTeX4 single column, 5 pages, 1 figure, final published versio
The two-impurity Kondo model with spin-orbit interactions
We study the two-impurity Kondo model (TIKM) in two dimensions with
spin-orbit coupled conduction electrons. In the first part of the paper we
analyze how spin-orbit interactions of Rashba as well as Dresselhaus type
influence the Kondo and RKKY interactions in the TIKM, generalizing results
obtained by H. Imamura {\em et al.} (2004) and J. Malecki (2007). Using our
findings we then explore the effect from spin-orbit interactions on the
non-Fermi liquid quantum critical transition between the RKKY-singlet and
Kondo-screened RKKY-triplet states. We argue that spin-orbit interactions under
certain conditions produce a line of critical points exhibiting the same
leading scaling behavior as that of the ordinary TIKM. In the second part of
the paper we shift focus and turn to the question of how spin-orbit
interactions affect the entanglement between two localized RKKY-coupled spins
in the parameter regime where the competition from the direct Kondo interaction
can be neglected. Using data for a device with two spinful quantum dots
patterned in a gated InAs heterostructure we show that a gate-controlled
spin-orbit interaction may drive a maximally entangled state to one with
vanishing entanglement, or vice versa (as measured by the concurrence). This
has important implications for proposals using RKKY interactions for nonlocal
control of qubit entanglement in semiconductor heterostructures.Comment: Revised version; new title and introduction in response to referee
suggestion, expanded discussion of results, added references. 14 pages, 5
figure
An order parameter for impurity systems at quantum criticality
A quantum phase transition may occur in the ground state of a system at zero
temperature when a controlling field or interaction is varied. The resulting
quantum fluctuations which trigger the transition produce scaling behavior of
various observables, governed by universal critical exponents. A particularly
interesting class of such transitions appear in systems with quantum impurities
where a non-extensive term in the free energy becomes singular at the critical
point. Curiously, the notion of a conventional order parameter which exhibits
scaling at the critical point is generically missing in these systems. We here
explore the possibility to use the Schmidt gap, which is an observable obtained
from the entanglement spectrum, as an order parameter. A case study of the
two-impurity Kondo model confirms that the Schmidt gap faithfully captures the
scaling behavior by correctly predicting the critical exponent of the
dynamically generated length scale at the critical point.Comment: 6 pages, 5 figure
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