関連する実験動画

Updated: Mar 1, 2026

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

Published on: March 30, 2017

フェルミ液体³Heにおける横ゼロ音の限界

Man Dinh Nguyen¹, Daehan Park¹, John William Scott¹

¹Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA.

Science advances

|February 27, 2026

Abstract:

Landau predicted that transverse sound propagates in a Fermi liquid with sufficiently strong interactions such as for liquid ³He, unlike a classical fluid that cannot support shear oscillations. Previous attempts to observe this unique collective mode yielded inconclusive results. We microfabricated acoustic cavities with a micrometer-scale path length that is suitable for direct detection of this sound mode and used the interference fringes from our acoustic Fabry-Pérot cavities to determine both real and imaginary parts of the acoustic impedance. No interference was observed. Either transverse sound does not exist or its attenuation must be very high, well above 2000 per centimeter. We discuss a theoretical framework for such high attenuation.

さらに関連する動画

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

Published on: October 9, 2012

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

Published on: June 28, 2016

関連する概念動画

Fermi Level

Fermi Level

The Fermi-Dirac function is represented by an S-shaped curve indicating the probability of an energy state being occupied by an electron at a given temperature. The Fermi level is the energy level at which there is a fifty percent chance of finding an electron, and it is positioned between the lower-energy valence band and the higher-energy conduction band.
At absolute zero temperature, electrons fill all energy states up to the Fermi level, leaving upper states empty. As the temperature rises,...

Fermi Level Dynamics

Fermi Level Dynamics

The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...

Atomic Nuclei: Nuclear Spin State Population Distribution

Atomic Nuclei: Nuclear Spin State Population Distribution

Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.

Speed of Sound in Solids and Liquids

Speed of Sound in Solids and Liquids

Most solids and liquids are incompressible—their densities remain constant throughout. In the presence of an external force, the molecules tend to restore to their original positions, which is only possible because the constituents interact. The interactions help the constituents pass on information about external disturbances, like sound waves. Therefore, sound waves travel faster through these media. Compared to solids, the constituents in a liquid are less tightly bound. Thus, sound...

Superconductor

Superconductor

A substance that reaches superconductivity, a state in which magnetic fields cannot penetrate, and there is no electrical resistance, is referred to as a superconductor. In 1911, Heike Kamerlingh Onnes of Leiden University, a Dutch physicist, observed a relation between the temperature and the resistance of the element mercury. The mercury sample was then cooled in liquid helium to study the linear dependence of resistance on temperature. It was observed that, as the temperature decreased, the...

Zeroth Law of Thermodynamics

Zeroth Law of Thermodynamics

Experimentally, if object A is in equilibrium with object B, and object B is in equilibrium with object C, then object A is in equilibrium with object C. That statement of transitivity is called the "zeroth law of thermodynamics." For example, a cold metal block and a hot metal block are both placed on a metal plate at room temperature. Eventually, the cold block and the plate will be in thermal equilibrium. In addition, the hot block and the plate will be in thermal equilibrium.