982 research outputs found
Fractional Quantum Hall Effect of Hard-Core Bosons in Topological Flat Bands
Recent proposals of topological flat band (TFB) models have provided a new
route to realize the fractional quantum Hall effect (FQHE) without Landau
levels. We study hard-core bosons with short-range interactions in two
representative TFB models, one of which is the well known Haldane model (but
with different parameters). We demonstrate that FQHE states emerge with
signatures of even number of quasi-degenerate ground states on a torus and a
robust spectrum gap separating these states from higher energy spectrum. We
also establish quantum phase diagrams for the filling factor 1/2 and illustrate
quantum phase transitions to other competing symmetry-breaking phases.Comment: 4 pages, 6 figure
Four-Step Evolution of Spin-Hall Conductance: Tight-Binding Electrons with Rashba Coupling in a Magnetic Field
An intriguing magneto-transport property is demonstrated by tight-binding
lattice electrons with Rashba spin-orbit coupling (SOC) in a magnetic field.
With the flux strength ( is an integer) and the Zeeman
splitting fixed, when increasing the Rashba SOC , the spin-Hall and
charge-Hall conductances (SHC and CHC) undergo four-step evolutions: the SHC
shows size-dependent resonances and jumps at three critical 's,
and changes its sign at and ; while the CHC
exhibits three quantum jumps by , and . Such
four-step evolutions are also reflected in topological characters and spin
polarizations of edge states of a cylindrical system, and are robust against
weak disorder.Comment: 4 pages, 5 figure
QED and relativistic nuclear recoil corrections to the 413 nm tune-out wavelength for the 2\,^3S_1 state of helium
Comparison of high accuracy calculations with precision measurement of the
413 nm tune-out wavelength of the He(2\,^3S_1) state provides a unique test
of quantum electro-dynamic (QED). We perform large-scale
relativistic-configuration-interaction (RCI) calculations of the tune-out
wavelength, that include the mass-shift operator, and fully account for leading
relativistic nuclear recoil terms in the Dirac-Coulomb-Breit (DCB) Hamiltonian.
We obtain the QED correction to the tune-out wavelength using perturbation
theory, and the effect of finite nuclear size is also evaluated. The resulting
tune-out wavelengths for the 2\,^3S_1(M_J=0) and 2\,^3S_1(M_J=\pm 1) states
are 413.084 26(4) nm and 413.090 15(4) nm, respectively. Compared with the only
current experimental value of 413.0938(9stat)(20syst) nm for the
2\,^3S_1(M_J=\pm 1) state, there is 1.8 discrepancy between present
theoretical work and experiment, which stimulates further theoretical and
higher-precision experimental investigations on the 413 nm tune-out wavelength.
In addition, we also determine the QED correction for the static dipole
polarizability of the He(2\,^3S_1) state to be 22.5 ppm, which may enable a
new test of QED in the future.Comment: 6 pages; 2 figure
Experimentally obtaining the Likeness of Two Unknown Quantum States on an NMR Quantum Information Processor
Recently quantum states discrimination has been frequently studied. In this
paper we study them from the other way round, the likeness of two quantum
states. The fidelity is used to describe the likeness of two quantum states.
Then we presented a scheme to obtain the fidelity of two unknown qubits
directly from the integral area of the spectra of the assistant qubit(spin) on
an NMR Quantum Information Processor. Finally we demonstrated the scheme on a
three-qubit quantum information processor. The experimental data are consistent
with the theoretical expectation with an average error of 0.05, which confirms
the scheme.Comment: 3 pages, 4 figure
Gene Deletion in Barley Mediated by LTR-retrotransposon BARE
A poly-row branched spike (prbs) barley mutant was obtained from soaking a two-rowed barley inflorescence in a solution of maize genomic DNA. Positional cloning and sequencing demonstrated that the prbs mutant resulted from a 28 kb deletion including the inflorescence architecture gene HvRA2. Sequence annotation revealed that the HvRA2 gene is flanked by two LTR (long terminal repeat) retrotransposons (BARE) sharing 89% sequence identity. A recombination between the integrase (IN) gene regions of the two BARE copies resulted in the formation of an intact BARE and loss of HvRA2. No maize DNA was detected in the recombination region although the flanking sequences of HvRA2 gene showed over 73% of sequence identity with repetitive sequences on 10 maize chromosomes. It is still unknown whether the interaction of retrotransposons between barley and maize has resulted in the recombination observed in the present study.Peer reviewe
Even-Odd Layer-Dependent Anomalous Hall Effect in Topological Magnet MnBi2Te4 Thin Films
A central theme in condensed matter physics is to create and understand the
exotic states of matter by incorporating magnetism into topological materials.
One prime example is the quantum anomalous Hall (QAH) state. Recently, MnBi2Te4
has been demonstrated to be an intrinsic magnetic topological insulator and the
QAH effect was observed in exfoliated MnBi2Te4 flakes. Here, we used molecular
beam epitaxy (MBE) to grow MnBi2Te4 films with thickness down to 1 septuple
layer (SL) and performed thickness-dependent transport measurements. We
observed a non-square hysteresis loop in the antiferromagnetic state for films
with thickness greater than 2 SL. The hysteresis loop can be separated into two
AH components. Through careful analysis, we demonstrated that one AH component
with the larger coercive field is from the dominant MnBi2Te4 phase, while the
other AH component with the smaller coercive field is from the minor Mn-doped
Bi2Te3 phase in the samples. The extracted AH component of the MnBi2Te4 phase
shows a clear even-odd layer-dependent behavior, a signature of
antiferromagnetic thin films. Our studies reveal insights on how to optimize
the MBE growth conditions to improve the quality of MnBi2Te4 films, in which
the QAH and other exotic states are predicted.Comment: 23 pages, 4 figures, comments are welcom
On the Ground State of Two Flavor Color Superconductor
The diquark condensate susceptibility in neutral color superconductor at
moderate baryon density is calculated in the frame of two flavor
Nambu-Jona-Lasinio model. When color chemical potential is introduced to keep
charge neutrality, the diquark condensate susceptibility is negative in the
directions without diquark condensate in color space, which may be regarded as
a signal of the instability of the conventional ground state with only diquark
condensate in the color 3 direction.Comment: 4 pages, 2 figure
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