513 research outputs found

### Effective spin-fermion model for strongly correlated electrons

A modified spin-fermion model is proposed to describe the physics of the
underdoped phase of the t-J model of strongly correlated electron

### Limitations of the mean field slave-particle approximations

We show that the transformation properties of the mean field slave
boson/fermion order parameters under an action of the global SU(2) group impose
certain restrictions on their applications to describe the phase diagram of the
t-J model.Comment: to appear in Phys. Rev.

### On the extra phase correction to the semiclassical spin coherent-state propagator

The problem of an origin of the Solary-Kochetov extra-phase contribution to
the naive semiclassical form of a generalized phase-space propagator is
addressed with the special reference to the su(2) spin case which is the most
important in applications. While the extra-phase correction to a flat
phase-space propagator can straightforwardly be shown to appear as a difference
between the principal and the Weyl symbols of a Hamiltonian in the
next-to-leading order expansion in the semiclassical parameter, the same
statement for the semiclassical spin coherent-state propagator holds provided
the Holstein-Primakoff representation of the su(2) algebra generators is
employed.Comment: 19 pages, no figures; a more general treatment is presented, some
references are added, title is slightly changed; submitted to JM

### On representation of the t-J model via spin-charge variables

We show that the t-J Hamiltonian is not in general reduced to H(S,f), where S
and f stand for independent ([S,f]=0) SU(2) (spin) generators and spinless
fermionic (hole) field, respectively. The proof is based upon an identification
of the Hubbard operators with the generators of the su(2|1) superalgebra in the
degenerate fundamental representation and ensuing SU(2|1) path integral
representation of the partition function.Comment: 15 pages, latex, no figure

### Electronic properties of disclinated flexible membrane beyond the inextensional limit: Application to graphene

Gauge-theory approach to describe Dirac fermions on a disclinated flexible
membrane beyond the inextensional limit is formulated. The elastic membrane is
considered as an embedding of 2D surface into R^3. The disclination is
incorporated through an SO(2) gauge vortex located at the origin, which results
in a metric with a conical singularity. A smoothing of the conical singularity
is accounted for by replacing a disclinated rigid plane membrane with a
hyperboloid of near-zero curvature pierced at the tip by the SO(2) vortex. The
embedding parameters are chosen to match the solution to the von Karman
equations. A homogeneous part of that solution is shown to stabilize the
theory. The modification of the Landau states and density of electronic states
of the graphene membrane due to elasticity is discussed.Comment: 15 pages, Journal of Physics:Condensed Matter in pres

### Classical and quantum dynamics of a spin-1/2

We reply to a comment on `Semiclassical dynamics of a spin-1/2 in an
arbitrary magnetic field'.Comment: 4 pages, submitted to Journal of Physics

### Spin-flip induced superfluidity in a ring of spinful hard-core bosons

The t - J Hamiltonian of the spinful hard-core bosonic ring in the Nagaoka
limit is solved. The energy spectrum becomes quantized due to presence of spin,
where each energy level corresponds to a cyclic permutation state of the spin
chains. The ground state is true ferromagnetic when the ring contains N = 2, 3
spinful hard-core bosons; for all other N it is a mixture of the ferromagnetic
and non-ferromagnetic states. This behaviour is different from the fermionic
ring, where ground state is true ferromagnetic only for N = 3. It is shown that
the intrinsic spin generated gauge fields are analogous to the synthetic gauge
fields generated by rotation of either the condensate or the confining
potential. It is argued that the low lying excited levels of the spin flipped
states intrinsically support the superfluidity. Possible ways to experimentally
verify these results are also discussed.Comment: main text in 6 pages, 2 figures; supplementary materials in 7 page

### Ising t-J model close to half filling: A Monte Carlo study

Within the recently proposed doped-carrier representation of the projected
lattice electron operators we derive a full Ising version of the t-J model.
This model possesses the global discrete Z_2 symmetry as a maximal spin
symmetry of the Hamiltonian at any values of the coupling constants, t and J.
In contrast, in the spin anisotropic limit of the t-J model, usually referred
to as the t-J_z model, the global SU(2) invariance is fully restored at J_z=0,
so that only the spin-spin interaction has in that model the true Ising form.
We discuss a relationship between those two models and the standard isotropic
t-J model. We show that the low-energy quasiparticles in all three models share
the qualitatively similar properties at low doping and small values of J/t. The
main advantage of the proposed Ising t-J model over the t-J_z one is that the
former allows for the unbiased Monte Carlo calculations on large clusters of up
to 10^3 sites. Within this model we discuss in detail the destruction of the
antiferromagnetic order by doping as well as the interplay between the AF order
and hole mobility. We also discuss the effect of the exchange interaction and
that of the next nearest neighbour hoppings on the destruction of the AF order
at finite doping. We show that the short-range AF order is observed in a wide
range of temperatures and dopings, much beyond the boundaries of the AF phase.
We explicitly demonstrate that the local no double occupancy constraint plays
the dominant role in destroying the magnetic order at finite doping. Finally, a
role of inhomogeneities is discussed.Comment: 24 pages, 10 figure

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