16,206 research outputs found
Spin-charge separation: From one hole to finite doping
In the presence of nonlocal phase shift effects, a quasiparticle can remain
topologically stable even in a spin-charge separation state due to the
confinement effect introduced by the phase shifts at finite doping. True
deconfinement only happens in the zero-doping limit where a bare hole can lose
its integrity and decay into holon and spinon elementary excitations. The Fermi
surface structure is completely different in these two cases, from a large
band-structure-like one to four Fermi points in one-hole case, and we argue
that the so-called underdoped regime actually corresponds to a situation in
between.Comment: 4 pages, 2 figures, presented in M2S-HTSC-VI conference (2000
Phase String Effect in the t-J Model: General Theory
We reexamine the problem of a hole moving in an antiferromagnetic spin
background and find that the injected hole will always pick up a sequence of
nontrivial phases from the spin degrees of freedom. Previously unnoticed, such
a string-like phase originates from the hidden Marshall signs which are
scrambled by the hopping of the hole. We can rigorously show that this phase
string is non-repairable at low energy and give a general proof that the
spectral weight Z must vanish at the ground-state energy due to the phase
string effect. Thus, the quasiparticle description fails here and the quantum
interference effect of the phase string dramatically affects the long-distance
behavior of the injected hole. We introduce a so-called phase-string
formulation of the t-J model for a general number of holes in which the phase
string effect can be explicitly tracked. As an example, by applying this new
mathematical formulation in one dimension, we reproduce the well-known
Luttinger-liquid behaviors of the asymptotic single-electron Green's function
and the spin-spin correlation function. We can also use the present phase
string theory to justify previously developed spin-charge separation theory in
two dimensions, which offers a systematic explanation for the transport and
magnetic anomalies in the high-T_c cuprates.Comment: Revtex, 36 pages, no figure, to appear in Phys. Rev. B
Neutrino masses and mixings
We propose a novel theoretical understanding of neutrino masses and mixings,
which is attributed to the intrinsic vector-like feature of the regularized
Standard Model at short distances. We try to explain the smallness of Dirac
neutrino masses and the decoupling of the right-handed neutrino as a free
particle. Neutrino masses and mixing angles are completely related to each
other in the Schwinger-Dyson equations for their self-energy functions. The
solutions to these equations and a possible pattern of masses and mixings are
discussed.Comment: LaTex 11 page
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