290 research outputs found
Thermal conductivity of suspended pristine graphene measured by Raman spectroscopy
The thermal conductivity of suspended single-layer graphene was measured as a
function of temperature using Raman scattering spectroscopy on clean samples
prepared directly on a prepatterned substrate by mechanical exfoliation without
chemical treatments. The temperature at the laser spot was monitored by the
frequency of the Raman 2 band of the Raman scattering spectrum, and the
thermal conductivity was deduced by analyzing heat diffusion equations assuming
that the substrate is a heat sink at ambient temperature. The obtained thermal
conductivity values range from 1800 WmK near 325 K to
710 WmK at 500 K.Comment: 4pages, 3 figure
Linking emergent phenomena and broken symmetries through one-dimensional objects and their dot/cross products
The symmetry of the whole experimental setups, including specific sample
environments and measurables, can be compared with that of specimens for
observable physical phenomena. We, first, focus on one-dimensional (1D)
experimental setups, independent from any spatial rotation around one
direction, and show that eight kinds of 1D objects (four; vectorlike, the other
four; director-like), defined in terms of symmetry, and their dot and cross
products are an effective way for the symmetry consideration. The dot products
form a Z2xZ2xZ2 group with Abelian additive operation, and the cross products
form a Z2xZ2 group with Abelian additive operation or Q8, a non-abelian group
of order eight, depending on their signs. Those 1D objects are associated with
characteristic physical phenomena. When a 3D specimen has Symmetry Operational
Similarity (SOS) with (identical or lower, but not higher, symmetries than) an
1D object with a particular phenomenon, the 3D specimen can exhibit the
phenomenon. This SOS approach can be a transformative and unconventional avenue
for symmetry-guided materials designs and discoveries.Comment: 12 pages, 6 figure
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