20 research outputs found
The effect of phase fluctuations on the single-particle properties of the underdoped cuprates
We study the effect of order parameter phase fluctuations on the
single-particle properties of fermions in the underdoped cuprate
superconductors using a phenomenological low-energy theory. We identify the
fermion-phase field coupling as the Doppler-shift of the quasiparticle spectrum
induced by the fluctuating superfluid velocity and we calculate the effect of
these fluctuations on the fermion self-energy. We show that the vortex pair
unbinding near the superconducting transition causes a significant broadening
in the fermion spectral function, producing a pseudogap-like feature. We also
discuss the specific heat and show that the phase fluctuation effect is visible
due to the short coherence length.Comment: RevTex 11 pages; 11 epsf figures included. Added and updated
reference
Midgap edge states and pairing symmetry of quasi-one-dimensional organic superconductors
The singlet s-, d- and triplet p-wave pairing symmetries in
quasi-one-dimensional organic superconductors can be experimentally
discriminated by probing the Andreev bound states at the sample edges. These
states have the energy in the middle of the superconducting gap and manifest
themselves as a zero-bias peak in tunneling conductance into the corresponding
edge. Their existence is related to the sign change of the pairing potential
around the Fermi surface. We present an exact self-consistent solution of the
edge problem showing the presence of the midgap states for p_x-wave
superconductivity. The spins of the edge state respond paramagnetically to a
magnetic field parallel to the vector d that characterizes triplet pairing.Comment: 6 pages, 4 figures. V.2: New section on spin response is added and
references are updated. V.3: Final version accepted to PRB. Typos are
corrected and important note is added in proof
Contraction-Induced Changes in Hydrogen Bonding of Muscle Hydration Water
Protein–water
interaction plays a crucial role in protein
dynamics and hence function. To study the chemical environment of
water and proteins with high spatial resolution, synchrotron radiation-Fourier
transform infrared (SR-FTIR) spectromicroscopy was used to probe skeletal
muscle myofibrils. Observing the OH stretch band showed that water
inside of relaxed myofibrils is extensively hydrogen-bonded with little
or no free OH. In higher-resolution measurements obtained with single
isolated myofibrils, the water absorption peaks were relatively higher
within the center region of the sarcomere compared to those in the
I-band region, implying higher hydration capacity of thick filaments
compared to the thin filaments. When specimens were activated, changes
in the OH stretch band showed significant dehydrogen bonding of muscle
water; this was indicated by increased absorption at ∼3480
cm<sup>–1</sup> compared to relaxed myofibrils. These contraction-induced
changes in water were accompanied by splitting of the amide I (Cî—»O)
peak, implying that muscle proteins transition from α-helix
to β-sheet-rich structures. Hence, muscle contraction can be
characterized by a loss of order in the muscle–protein complex,
accompanied by a destructuring of hydration water. The findings shed
fresh light on the molecular mechanism of muscle contraction and motor
protein dynamics