Title: How heat propagates in `non-Fermi liquid' $^3$He Show Chinese title

Title: 热量如何在“非费米液体”$^3$中传播

Abstract: In Landau's Fermi liquid, transport is governed by scattering between quasi-particles. The normal liquid $^3$He conforms to this picture, but only when T$< 0.02$ T$_F$. Here, we observe that the deviation from the standard behavior is concomitant with the fermion-fermion scattering time falling below the Planckian time, $\frac{\hbar}{k_BT}$. The thermal diffusivity of this quantum liquid is bounded by a minimum set by fundamental physical constants and earlier observed in classical liquids. This implies that collective excitations of the liquid (a sound mode) are carrying heat. We argue that if heat is carried by 2k$_F$ hydrodynamic sound mode, both the amplitude and the hitherto unexplained $T^{1/2}$ temperature dependence of thermal conductivity find an explanation with no other adjustable parameter. Show Chinese abstract

Abstract: 在朗道的费米液体中，输运由准粒子之间的散射所支配。 正常的液体$^3$氦符合这一图景，但仅当 T$< 0.02$ T$_F$时。 在这里，我们观察到，偏离标准行为与费米子-费米子散射时间低于普朗克时间$\frac{\hbar}{k_BT}$相伴随。 这种量子液体的热扩散率由由基本物理常数设定的最小值限制，并且之前在经典液体中已观察到。 这意味着液体的集体激发（一种声学模式）在传递热量。 我们认为，如果热量由 2k$_F$湍流声学模式传递，那么热导率的振幅以及迄今为止未解释的$T^{1/2}$温度依赖性将得到解释，而无需其他可调参数。