Eighty years of superfluidity

Halperin, W. P.

doi:10.1038/d41586-018-00417-7

Cited by 3 publications

(4 citation statements)

References 18 publications

(15 reference statements)

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“…It should also be noted that almost all materials would behave quite differently and, in some cases, might demonstrate unexpected properties at deep cryogenic temperatures, as compared to that at RT or even at liquid nitrogen temperature. For example, the well-known phenomena superconductivity ( 32 ) and superfluidity ( 33 ) were first discovered until the temperature was down to ~4 K. Therefore, studies for the properties (including mechanics) at such deep cryogenic temperatures should be important, and some unexpected properties might be observed.…”

Section: Introductionmentioning

confidence: 99%

Super-elasticity of three-dimensionally cross-linked graphene materials all the way to deep cryogenic temperatures

et al. 2019

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Until now, materials with high elasticity at deep cryogenic temperatures have not been observed. Previous reports indicated that graphene and carbon nanotube–based porous materials can exhibit reversible mechano-elastic behavior from liquid nitrogen temperature up to nearly a thousand degrees Celsius. Here, we report wide temperature–invariant large-strain super-elastic behavior in three-dimensionally cross-linked graphene materials that persists even to a liquid helium temperature of 4 K, a property not previously observed for any other material. To understand the mechanical properties of these graphene materials, we show by in situ experiments and modeling results that these remarkable properties are the synergetic results of the unique architecture and intrinsic elastic/flexibility properties of individual graphene sheets and the covalent junctions between the sheets that persist even at harsh temperatures. These results suggest possible applications for such materials at extremely low temperature environments such as those in outer space.

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Section: Introductionmentioning

confidence: 99%

Super-elasticity of three-dimensionally cross-linked graphene materials all the way to deep cryogenic temperatures

et al. 2019

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confidence: 99%

“…Quantum fluids, from superconducting electrons 1 to superfluid helium 2 , from ultracold atoms Bose-Einstein condensation (BEC) on optical lattices 3 to the cosmological-scale superfluid core in neutron stars 4 , embody exotic quantum behaviors emblematic of particles or excitations with bosonic statistics. The hydrodynamics of quantum fluids has been the source of tremendous interest in a multitude of many-body systems [1][2][3]5,6 . In particular, exciton-polaritons, quasiparticles composed of a superposition of the confined photons and excitons in a semiconductor microcavity, recently emerged as a unique driven-dissipative system for quantum fluid research 7 .…”

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confidence: 99%

Room-temperature polariton quantum fluids in halide perovskites

et al. 2022

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Quantum fluids exhibit quantum mechanical effects at the macroscopic level, which contrast strongly with classical fluids. Gain-dissipative solid-state exciton-polaritons systems are promising emulation platforms for complex quantum fluid studies at elevated temperatures. Recently, halide perovskite polariton systems have emerged as materials with distinctive advantages over other room-temperature systems for future studies of topological physics, non-Abelian gauge fields, and spin-orbit interactions. However, the demonstration of nonlinear quantum hydrodynamics, such as superfluidity and Čerenkov flow, which is a consequence of the renormalized elementary excitation spectrum, remains elusive in halide perovskites. Here, using homogenous halide perovskites single crystals, we report, in both one- and two-dimensional cases, the complete set of quantum fluid phase transitions from normal classical fluids to scatterless polariton superfluids and supersonic fluids—all at room temperature, clear consequences of the Landau criterion. Specifically, the supersonic Čerenkov wave pattern was observed at room temperature. The experimental results are also in quantitative agreement with theoretical predictions from the dissipative Gross-Pitaevskii equation. Our results set the stage for exploring the rich non-equilibrium quantum fluid many-body physics at room temperature and also pave the way for important polaritonic device applications.

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“…econd sound is a transport phenomenon of quantum liquids that emerges below the critical temperature for superfluidity T c [1][2][3] . It was experimentally discovered 4 in 1944 in He II 5 and was described with a hydrodynamic two-fluid model 2,[6][7][8] which treats He II as a mixture of a superfluid (SF) and a normal fluid (NF).…”

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confidence: 99%

Second sound in the crossover from the Bose-Einstein condensate to the Bardeen-Cooper-Schrieffer superfluid

et al. 2021

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Second sound is an entropy wave which propagates in the superfluid component of a quantum liquid. Because it is an entropy wave, it probes the thermodynamic properties of the quantum liquid. Here, we study second sound propagation for a large range of interaction strengths within the crossover between a Bose-Einstein condensate (BEC) and the Bardeen-Cooper-Schrieffer (BCS) superfluid, extending previous work at unitarity. In particular, we investigate the strongly-interacting regime where currently theoretical predictions only exist in terms of an interpolation in the crossover. Working with a quantum gas of ultracold fermionic 6Li atoms with tunable interactions, we show that the second sound speed varies only slightly in the crossover regime. By varying the excitation procedure, we gain deeper insight on sound propagation. We compare our measurement results with classical-field simulations, which help with the interpretation of our experiments.

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Eighty years of superfluidity

Cited by 3 publications

References 18 publications

Super-elasticity of three-dimensionally cross-linked graphene materials all the way to deep cryogenic temperatures

Super-elasticity of three-dimensionally cross-linked graphene materials all the way to deep cryogenic temperatures

Room-temperature polariton quantum fluids in halide perovskites

Second sound in the crossover from the Bose-Einstein condensate to the Bardeen-Cooper-Schrieffer superfluid

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