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In 1966, William Russell Abel, Ansel Cochran Anderson and John Charles Wheatley sent acoustic waves through bulk liquid helium-3 at $0.32\mathrm{atm}$ and frequencies $15.4$ and $45.5\mathrm{MHz}$. A quartz delay line and receiving acoustic transducer bounded a $0.138\mathrm{mm}$ liquid gap; shielding reduced electrical pickup. Powdered cerium magnesium nitrate provided magnetic thermometry during a slow warm-up. Pulse amplitudes measured acoustic attenuation; phase difference comparison measured velocity. Calibration pulses checked gain; early received cycles avoided multiple reflections. On cooling through a maximum, acoustic attenuation changed from $\alpha \propto {\omega }^2/T^{\ast 2}$ to $\alpha \propto T^{\ast 2}$ with a velocity shift supporting zero sound; $T^{\ast }$ is their magnetic temperature scale. Weak acoustic attenuation was harder to resolve.^[ref]

This 1966 test followed Lev Landau's 1962 Nobel Prize in Physics.^[ref]

The experiment concerned normal liquid helium-3, distinct from the later discovery of superfluid helium-3.^[ref] Landau's original papers are theoretical calculations, not reports of an apparatus.

Vitaly Lazarevich Ginzburg and Lev Landau applied an order parameter description to superconductivity in 1950. A spatially varying complex amplitude extends the fixed-amplitude description of the London equations. Their initial charge assumption preceded the later identification of the universal pair charge.^[ref]

Consider the following isotropic, local SI Helmholtz free energy model near a continuous superconducting transition temperature:Here $\beta >0$, $m_{\ast }>0$ is a phenomenological mass parameter, and $q=-2e$ fixes the electron-pair convention. The uniform superconducting minimum for $\alpha <0$ has $|{\psi }_0{|}^2=-\alpha /\beta$. The gradient term penalizes changes of the amplitude and the gauge-invariant quantum phase; the magnetic term penalizes magnetic field penetration. The gauge-coupling sign in Ginzburg-Landau superconductivity keeps the electric current and field equation consistent. This model omits material anisotropy, microscopic nonlocality and critical fluctuations.

Lev Landau developed descriptions of interacting quantum fluids through their elementary excitations. In the Landau critical velocity argument, creating an excitation of energy $ϵ(\mathbf{p})$ in flowing superfluid changes the relevant energy by $ϵ(\mathbf{p})-\mathbf{v}\cdot \mathbf{p}$. Requiring this to remain positive yields the ideal bound $v_c={\min }_pϵ(p)/p$; additional processes can limit actual flow at lower speeds.^[ref] His Fermi liquid theory explains how strongly interacting fermions can retain long-lived low-energy quasiparticles, with interactions modifying their effective mass and collective response.^[ref]

A physicist.^[ref]

Vitaly Ginzburg and Lev Landau described superconductivity through a spatially varying complex order parameter coupled to an electromagnetic vector potential. Their Ginzburg-Landau theory balances the cost of changing the order parameter with magnetic-field energy and the tendency to form a superconducting state. It predicts characteristic coherence and penetration lengths and supports analysis of surfaces, currents and nonuniform states. The theory is phenomenological: it can organize measurable behavior near a transition without first deriving the microscopic pairing interaction.^[ref]

A physicist who headed the Lebedev institute’s theoretical physics department from 1971 to 1988.^[ref]