23,322 research outputs found
Blue Phosphorene Oxide: Strain-tunable Quantum Phase Transitions and Novel 2D Emergent Fermions
Tunable quantum phase transitions and novel emergent fermions in solid state
materials are fascinating subjects of research. Here, we propose a new stable
two-dimensional (2D) material, the blue phosphorene oxide (BPO), which exhibits
both. Based on first-principles calculations, we show that its equilibrium
state is a narrow-bandgap semiconductor with three bands at low energy.
Remarkably, a moderate strain can drive a semiconductor-to-semimetal quantum
phase transition in BPO. At the critical transition point, the three bands
cross at a single point at Fermi level, around which the quasiparticles are a
novel type of 2D pseudospin-1 fermions. Going beyond the transition, the system
becomes a symmetry-protected semimetal, for which the conduction and valence
bands touch quadratically at a single Fermi point that is protected by
symmetry, and the low-energy quasiparticles become another novel type of 2D
double Weyl fermions. We construct effective models characterizing the phase
transition and these novel emergent fermions, and we point out several exotic
effects, including super Klein tunneling, supercollimation, and universal
optical absorbance. Our result reveals BPO as an intriguing platform for the
exploration of fundamental properties of quantum phase transitions and novel
emergent fermions, and also suggests its great potential in nanoscale device
applications.Comment: 23 pages, 5 figure
Entanglement dynamics of two-qubit system in different types of noisy channels
In this paper, we study entanglement dynamics of a two-qubit extended
Werner-like state locally interacting with independent noisy channels, i.e.,
amplitude damping, phase damping and depolarizing channels. We show that the
purity of initial entangled state has direct impacts on the entanglement
robustness in each noisy channel. That is, if the initial entangled state is
prepared in mixed instead of pure form, the state may exhibit entanglement
sudden death (ESD) and/or be decreased for the critical probability at which
the entanglement disappear.Comment: 11 pages, 6 figure
Comments on Higher Rank Wilson Loops in
For theory with gauge group we evaluate expectation
values of Wilson loops in representations described by a rectangular Young
tableau with rows and columns. The evaluation reduces to a two-matrix
model and we explain, using a combination of numerical and analytical
techniques, the general properties of the eigenvalue distributions in various
regimes of parameters where is the 't Hooft
coupling. In the large limit we present analytic results for the leading
and sub-leading contributions. In the particular cases of only one row or one
column we reproduce previously known results for the totally symmetry and
totally antisymmetric representations. We also extensively discusss the limit of the theory. While establishing these connections
we clarify aspects of various orders of limits and how to relax them; we also
find it useful to explicitly address details of the genus expansion. As a
result, for the totally symmetric Wilson loop we find new contributions that
improve the comparison with the dual holographic computation at one loop order
in the appropriate regime.Comment: 28 pages, 4 figures. v2: References added. v3: More references, JHEP
versio
Double pion production in and collisions
With an effective Lagrangian approach, we give a full analysis on the and reactions by exploring the roles of
various resonances with mass up to 1.72 GeV. We find large contributions from
, , and resonances. Our
calculations also indicate sizeable contributions from nucleon poles for the
energies close to the threshold. A good description to the existing data of
different isospin channels of and
for beam energies up to 2.2 GeV is reached. Our results provide important
implications to the ABC effect and guildlines to the future experimental
projects at COSY, HADES and HIRFL-CSR. We point out that the \={P}ANDA at FAIR
could be an essential place for studying the properties of baryon resonances
and the data with baryon and anti-baryon in final states are worth analyzing.Comment: Invited plenary talk at the 11th International Workshop on Meson
Production, Properties and Interaction (MESON2010), 10-15 June, 2010, Krakow,
Polan
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