1,559 research outputs found
Tomonaga Luttinger liquid in the topological edge channel of multilayer FeSe
A two dimensional topological insulator exhibits helical edge states
topologically protected against single particle backscattering. Such protection
breaks down, however, when electron electron interactions are significant or
when edge reconstruction occurs, leading to suppressed density of states (DOS)
at Fermi level that follows universal scaling with temperature and energy,
characteristic of Tomonaga Luttinger liquid (TLL). Here, we grow multilayer
FeSe on SrTiO3 by molecular beam epitaxy, and observe robust edge states at
both {100}Se and {110}Se steps using scanning tunneling
microscopy/spectroscopy. We determine the DOS follows a power law, resulting in
Luttinger parameter K of 0.26 +/- 0.02 and 0.43 +/- 0.07 for {100}Se and
{110}Se edges, respectively. The smaller K for the {100}Se edge also indicates
strong correlations, attributed to ferromagnetic ordering likely present due to
checkerboard antiferromagnetic fluctuations in FeSe. These results demonstrate
TLL in FeSe helical edge channels, providing an exciting model system for novel
topological excitations arising from superconductivity and interacting helical
edge states.Comment: 28 page
Finite size effects on hinge states in three-dimensional second-order topological insulators
We investigate the finite size effects of a three-dimensional second-order
topological insulator with fourfold rotational symmetry and time-reversal
symmetry. Starting from the effective Hamiltonian of the three-dimensional
second-order topological insulator, we derive the effective Hamiltonian of four
two-dimensional surface states with gaps derived by perturbative methods. Then,
the sign alternation of the mass term of the effective Hamiltonian on the
adjacent surface leads to the hinge state. In addition, we obtain the effective
Hamiltonian and its wave function of one-dimensional gapless hinge states with
semi-infinite boundary conditions based on the effective Hamiltonian of
two-dimensional surface states. In particular, we find that the hinge states on
the two sides of the same surface can couple to produce a finite energy gap
Orthogonality catastrophe and quantum speed limit for dynamical quantum phase transition
We investigate the orthogonality catastrophe and quantum speed limit in the
Creutz model for dynamical quantum phase transitions. We demonstrate that exact
zeros of the Loschmidt echo can exist in finite-size systems for specific
discrete values. We highlight the role of the zero-energy mode when analyzing
quench dynamics near the critical point. We also examine the behavior of the
time for the first exact zeros of the Loschmidt echo and the corresponding
quantum speed limit time as the system size increases. While the bound is not
tight, it can be attributed to the scaling properties of the band gap and
energy variance with respect to system size. As such, we establish a relation
between the orthogonality catastrophe and quantum speed limit by referencing
the full form of the Loschmidt echo. Significantly, we find the possibility of
using the quantum speed limit to detect the critical point of a static quantum
phase transition, along with a decrease in the amplitude of noise induced
quantum speed limit.Comment: 10 pages, 8 figure
Visualizing symmetry-breaking electronic orders in epitaxial Kagome magnet FeSn films
Kagome lattice hosts a plethora of quantum states arising from the interplay
of topology, spin-orbit coupling, and electron correlations. Here, we report
symmetry-breaking electronic orders tunable by an applied magnetic field in a
model Kagome magnet FeSn consisting of alternating stacks of two-dimensional
Fe3Sn Kagome and Sn2 honeycomb layers. On the Fe3Sn layer terminated FeSn thin
films epitaxially grown on SrTiO3(111) substrates, we observe trimerization of
the Kagome lattice using scanning tunneling microscopy/spectroscopy, breaking
its six-fold rotational symmetry while preserving the transitional symmetry.
Such a trimerized Kagome lattice shows an energy-dependent contrast reversal in
dI/dV maps, which is significantly enhanced by bound states induced by Sn
vacancy defects. This trimerized Kagome lattice also exhibits stripe
modulations that are energy-dependent and tunable by an applied in-plane
magnetic field, indicating symmetry-breaking nematicity from the entangled
magnetic and charge degrees of freedom in antiferromagnet FeSn
Tuning quantum paramagnetism and d-wave superconductivity in single-layer iron chalcogenides by chemical pressure
By substituting S into single-layer FeSe/SrTiO3, chemical pressure is applied
to tune its paramagnetic state that is modeled as an incoherent superposition
of spin-spiral states. The resulting electronic bands resemble an ordered
checkerboard antiferromagnetic structure, consistent with angle-resolved
photoemission spectroscopy measurements. Scanning tunneling spectroscopy
reveals a gap evolving from U-shaped for FeSe to V-shaped for FeS with
decreasing size, attributed to a d-wave superconducting state for which nodes
emerge once the gap size is smaller than the effective spin-orbit coupling
Quantum and classical correlations in the one-dimensional XY model with Dzyaloshinskii-Moriya interaction
We study the effect of Dzyaloshinskii-Moriya (DM) interaction on pairwise
quantum discord, entanglement, and classical correlation in the anisotropic XY
spin-half chain. Analytical expressions for both quantum and classical
correlations are obtained from the spin-spin correlation functions. We show
that these pairwise quantities exhibit various behaviors in relation to the
relative strengths of the DM interaction, the anisotropy and the magnetic
intensity. We observe non-analyticities of the derivatives of both quantum and
classical correlations with respect to the magnetic intensity at the critical
point, with consideration of the DM interaction.Comment: 18pages, 6figure
Effects of follicle-stimulating hormone on fat metabolism and cognitive impairment in women during menopause
Lipid metabolism disorder is a common pathological manifestation of menopausal women, and is also an important risk factor for many diseases at this stage of life. Epidemiological studies have shown that high levels of follicle-stimulating hormone (FSH) in menopausal women are closely associated with changes in body composition, central obesity, and cognitive decline. Exogenous FSH causes growth and proliferation of adipose, whereas blockage of the FSH signaling pathway leads to decline in adipose. Mechanistically, FSH, FSH receptor (FSHR), G protein coupling, gene mutation and other pathways are involved in adipogenesis and cognitive impairment. Here, we review the critical role and potential interactions of FSH in adipogenesis and cognitive impairment in menopausal women. Further understanding of the exact mechanisms of FSH aggravating obesity and cognitive impairment may provide a new perspective for promoting healthy aging in menopausal women
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