31,052 research outputs found
Optical conductivity of nodal metals
Fermi liquid theory is remarkably successful in describing the transport and
optical properties of metals; at frequencies higher than the scattering rate,
the optical conductivity adopts the well-known power law behavior
. We have observed an unusual non-Fermi
liquid response in the ground
states of several cuprate and iron-based materials which undergo electronic or
magnetic phase transitions resulting in dramatically reduced or nodal Fermi
surfaces. The identification of an inverse (or fractional) power-law behavior
in the residual optical conductivity now permits the removal of this
contribution, revealing the direct transitions across the gap and allowing the
nature of the electron-boson coupling to be probed. The non-Fermi liquid
behavior in these systems may be the result of a common Fermi surface topology
of Dirac cone-like features in the electronic dispersion.Comment: 8 pages including supplemental informatio
Chirality in Liquid Crystals: from Microscopic Origins to Macroscopic Structure
Molecular chirality leads to a wonderful variety of equilibrium structures,
from the simple cholesteric phase to the twist-grain-boundary phases, and it is
responsible for interesting and technologically important materials like
ferroelectric liquid crystals. This paper will review some recent advances in
our understanding of the connection between the chiral geometry of individual
molecules and the important phenomenological parameters that determine
macroscopic chiral structure. It will then consider chiral structure in
columnar systems and propose a new equilibrium phase consisting of a regular
lattice of twisted ropes.Comment: 20 pages with 6 epsf figure
Doping of a One-Dimensional Mott Insulator: Photoemision and Optical Studies of SrCuO
The spectral properties of a one-dimensional (1D) single-chain Mott insulator
SrCuO have been studied in angle-resolved photoemission and optical
spectroscopy, at half filling and with small concentrations of extra charge
doped into the chains via high oxygen pressure growth. The single- particle gap
is reduced with oxygen doping, but the metallic state is not reached. The
bandwidth of the charge-transfer band increases with doping, while the state
becomes narrower, allowing unambiguous observation of separated spinon and
holon branches in the doped system. The optical gap is not changed upon doping,
indicating that a shift of chemical potential rather than decrease of
corelation gap is responsible for the apparent reduction of the photoemission
gap.Comment: 4 pages, 2 figure
Thermodynamics of rotating Bose gases in a trap
Novel ground state properties of rotating Bose gases have been intensively
studied in the context of neutral cold atoms. We investigate the rotating Bose
gas in a trap from a thermodynamic perspective, taking the charged ideal Bose
gas in magnetic field (which is equivalent to a neutral gas in a synthetic
magnetic field) as an example. It is indicated that the Bose-Einstein
condensation temperature is irrelevant to the magnetic field, conflicting with
established intuition that the critical temperature decreases with the field
increasing. The specific heat and Landau diamagnetization also exhibit
intriguing behaviors. In contrast, we demonstrate that the condensation
temperature for neutral Bose gases in a rotating frame drops to zero in the
fast rotation limit, signaling a non-condensed quantum phase in the ground
state.Comment: 4 pages, 1 figur
Charge order, metallic behavior and superconductivity in La_{2-x}Ba_xCuO_4 with x=1/8
The ab-plane optical properties of a cleaved single crystal of
La_{2-x}Ba_xCuO_4 for x=1/8 (T_c ~ 2.4 K) have been measured over a wide
frequency and temperature range. The low-frequency conductivity is Drude-like
and shows a metallic response with decreasing temperature. However, below ~ 60
K, corresponding to the onset of charge-stripe order, there is a rapid loss of
spectral weight below about 40 meV. The gapping of single-particle excitations
looks surprisingly similar to that observed in superconducting
La_{2-x}Sr_{x}CuO_4, including the presence of a residual Drude peak with
reduced weight; the main difference is that the lost spectral weight moves to
high, rather than zero, frequency, reflecting the absence of a bulk
superconducting condensate.Comment: 4 pages, with 1 table and 3 figure
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