8,986 research outputs found
Topological phase transition from nodal to nodeless d-wave superconductivity in electron-doped cuprate superconductors
Unlike the hole-doped cuprates, both nodal and nodeless superconductivity
(SC) are observed in the electron-doped cuprates. To understand these two types
of SC states, we propose a unified theory by considering the two-dimensional
t-J model in proximity to an antiferromagnetic (AF) long-range ordering state.
Within the slave-boson mean-field approximation, the d-wave pairing symmetry is
still the most energetically favorable even in the presence of the external AF
field. In the nodal phase, it is found that the nodes carry vorticity and are
protected by the adjoint symmetry of time-reversal and one unit lattice
translation. Robust edge modes are obtained, suggesting the nodal d-wave SC
being a topological weak-pairing phase. As decreasing the doping concentration
or increasing the AF field, the nodes with opposite vorticity annihilate and
the nodeless strong-pairing phase emerges. The topological phase transition is
characterized by a critical point with anisotropic Bogoliubov quasiparticles,
and a universal understanding is thus established for all electron-doped
cuprates.Comment: 7 pages, 5 figures; published versio
Tuning a magnetic Feshbach resonance with spatially modulated laser light
We theoretically investigate the control of a magnetic Feshbach resonance
using a bound-to-bound molecular transition driven by spatially modulated laser
light. Due to the spatially periodic coupling between the ground and excited
molecular states, there exists a band structure of bound states, which can
uniquely be characterized by some extra bumps in radio-frequency spectroscopy.
With the increasing of coupling strength, the series of bound states will cross
zero energy and directly result in a number of scattering resonances, whose
position and width can be conveniently tuned by the coupling strength of the
laser light and the applied magnetic field (i.e., the detuning of the ground
molecular state). In the presence of the modulated laser light, universal
two-body bound states near zero-energy threshold still exist. However, compared
with the case without modulation, the regime for such universal states is
usually small. An unified formula which embodies the influence of the modulated
coupling on the resonance width is given. The spatially modulated coupling also
implies a local spatially varying interaction between atoms. Our work proposes
a practical way of optically controlling interatomic interactions with high
spatial resolution and negligible atomic loss.Comment: 9pages, 5figur
Two-dimensional topological superconducting phases emerged from d-wave superconductors in proximity to antiferromagnets
Motivated by the recent observations of nodeless superconductivity in the
monolayer CuO grown on the BiSrCaCuO
substrates, we study the two-dimensional superconducting (SC) phases described
by the two-dimensional - model in proximity to an antiferromagnetic (AF)
insulator. We found that (i) the nodal d-wave SC state can be driven via a
continuous transition into a nodeless d-wave pairing state by the proximity
induced AF field. (ii) The energetically favorable pairing states in the strong
field regime have extended s-wave symmetry and can be nodal or nodeless. (iii)
Between the pure d-wave and s-wave paired phases, there emerge two
topologically distinct SC phases with (i) symmetry, i.e., the weak and
strong pairing phases, and the weak pairing phase is found to be a
topological superconductor protected by valley symmetry, exhibiting robust
gapless non-chiral edge modes. These findings strongly suggest that the
high- superconductors in proximity to antiferromagnets can realize fully
gapped symmetry protected topological SC.Comment: 7 pages, 4 figures; revised versio
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