arXiv subjects

H. L. Yu

Publications and source records attributed to H. L. Yu.

3 recordsLinked to original sources

arXiv2017

Liquid-like thermal conduction in a crystalline solid

A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations. Here, we report that the crystalline solid AgCrSe2 has liquid-like thermal conduction. In this compound, Ag atoms exhibit a dynamic duality that they are exclusively involved in intense low-lying transverse acoustic phonons while they also undergo local fluctuations inherent in an order-to-disorder transition occurring at 450 K. As a consequence of this extreme disorder-phonon coupling, transverse acoustic phonons become damped as approaching the transition temperature, above which they are not defined anymore because their lifetime is shorter than the relaxation time of local fluctuations. Nevertheless, the damped longitudinal acoustic phonon survives for thermal transport. This microscopic insight might reshape the fundamental idea on thermal transport properties of matter and facilitates the optimization of thermoelectrics.

cond-mat.mtrl-sci↗

arXiv1993

Corrections to Chiral Dynamics of Heavy Hadrons: (I) 1/M Correction

In earlier publications we have analyzed the strong and radiative decays of heavy hadrons in a formalism which incorporates both heavy-quark and chiral symmetries. In particular, we have derived a heavy-hadron chiral Lagrangian whose coupling constants are related by the heavy-quark flavor-spin symmetry arising from the QCD Lagrangian with infinitely massive quarks. In this paper, we re-examine the structure of the above chiral Lagrangian by including the effects of $1/m_Q$ corrections in the heavy quark effective theory. The relations among the coupling constants, originally derived in the heavy-quark limit, are modified by heavy quark symmetry breaking interactions in QCD. Some of the implications are discussed.

hep-ph↗

arXiv1992

Chiral Lagrangians for Radiative Decays of Heavy Hadrons

The radiative decays of heavy mesons and heavy baryons are studied in a formalism which incorporates both the heavy quark symmetry and the chiral symmetry. The chiral Lagrangians for the electromagnetic interactions of heavy hadrons consist of two pieces: one from gauging electromagnetically the strong-interaction chiral Lagrangian, and the other from the anomalous magnetic moment interactions of the heavy baryons and mesons. Due to the heavy quark spin symmetry, the latter contains only one independent coupling constant in the meson sector and two in the baryon sector. These coupling constants only depend on the light quarks and can be calculated in the nonrelativistic quark model. However, the charm quark is not heavy enough and the contribution from its magnetic moment must be included. Applications to the radiative decays $D^\ast \rightarrow D γ~,~B^\ast \rightarrow B γ~,~ Ξ^\prime_c \rightarrow Ξ_c γ~, Σ_c \rightarrow Λ_c γ$ and $Σ_c \rightarrow Λ_c πγ$ are given. Together with our previous results on the strong decay rates of $D^\ast \rightarrow D π$ and $Σ_c \rightarrow Λ_c π$, predictions are obtained for the total widths and branching ratios of $D^\ast$ and $Σ_c$. The decays $Σ^+_c \rightarrow Λ^+_c π^0 γ$ and $Σ^0_c \rightarrow Λ^+_c π^- γ$ are discussed to illustrate the important roles played by both the heavy quark symmetry and the chiral symmetry.

hep-ph↗