Quantum Solid properties, the Supersolid state, and the Vortex State (original) (raw)
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Journal of The Physical Society of Japan, 2008
The possibility of a supersolid state of matter, i.e., a crystalline solid exhibiting superfluid properties, first appeared in theoretical studies about forty years ago. After a long period of little interest due to the lack of experimental evidence, it has attracted strong experimental and theoretical attention in the last few years since Kim and Chan (Penn State, USA) reported evidence for nonclassical rotational inertia effects, a typical signature of superfluidity, in samples of solid 4He. Since this "first observation", other experimental groups have observed such effects in the response to the rotation of samples of crystalline helium, and it has become clear that the response of the solid is extremely sensitive to growth conditions, annealing processes, and 3He impurities. A peak in the specific heat in the same range of temperatures has been reported as well as anomalies in the elastic behaviour of solid 4He with a strong resemblance to the phenomena revealed by torsional oscillator experiments. Very recently, the observation of unusual mass transport in hcp solid 4He has also been reported, suggesting superflow. From the theoretical point of view, powerful simulation methods have been used to study solid 4He, but the interpretation of the data is still rather difficult; dealing with the question of supersolidity means that one has to face not only the problem of the coexistence of quantum coherence phenomena and crystalline order, exploring the realm of spontaneous symmetry breaking and quantum field theory, but also the problem of the role of disorder, i.e., how defects, such as vacancies, impurities, dislocations, and grain boundaries, participate in the phase transition mechanism.
Evidence for a Superglass State in Solid 4 He
Science, 2009
Glasslike Supersolid Recent experiments with solid helium confined to the ring of a torsional oscillator at extremely low temperatures have been interpreted in terms of an exotic supersolid phase—a crystalline solid that somehow flows like a superfluid. However, behavioral differences between samples have raised many questions (see the Perspective by Saunders ). Hunt et al. (p. 632 ) present a comprehensive study of the relaxation dynamics of the torsional oscillator system as a function of time and temperature. The data provides evidence for a “supersolid glass,” where glassy behavior of crystal dislocations and superfluidity can coexist. In a separate theoretical study, Anderson (p. 631 ) argues that supersolidity ought to be a ground state for all bose solids, but that defects in the sample may mask the supersolid signature.
Local Stress and Superfluid Properties of Solid He4
Physical Review Letters, 2008
More than half a century ago Penrose asked : are the superfluid and solid state of matter mutually exclusive or do there exist "supersolid" materials where the atoms form a regular lattice and simultaneously flow without friction? Recent experiments provide evidence that supersolid behavior indeed exists in 4 He -the most quantum material known in Nature. In this paper we show that large local strain in the vicinity of crystalline defects is the origin of supersolidity in 4 He. Although ideal crystals of 4 He are not supersolid, the gap for vacancy creation closes when applying a moderate stress. While a homogeneous system simply becomes unstable at this point, the stressed core of crystalline defects (dislocations and grain boundaries) undergoes a radical transformation and can become superfluid.
Supersolid He4 likely has nearly isotropic superflow
Physical Review B, 2006
We extend previous calculations of the zero temperature superfluid fraction f s (SFF) vs localization, from the fcc lattice to the experimentally realized (for solid 4 He) hcp and bcc lattices.
Solid 4He : search for superfluidity
Journal de Physique, 1989
2014 L'existence d'une superfluidité pour un solide de bosons a été proposée par plusieurs théoriciens. Aucune expérience ne l'a jusqu'à présent révélée. Nous présentons un argument qui nous a incités à explorer la gamme de température 1 mK-20 mK. Nous avons tenté de détecter un courant de masse à travers du 4He solide à 4 mK. L'absence d'effet abaisse encore la borne supérieure pour la température de superfluidité de ce solide. Abstract. 2014 Theoreticians agree that superfluidity can exist in a Bose solid. The experiments to detect such an effect have failed up to now. We present here an argument that justifies the exploration of the 1 mK-20 mK temperature range. We have carried out an experiment to detect a mass flow through the solid 4He down to 4 mK. No anomalous effect occurred, and this result therefore further reduces the upper limit for the occurrence of superfluidity in solid 4He to below 4 mK. 1bme 50 N° 15 1er AOUT 1989
Torsional oscillators and the entropy dilemma of putative supersolid 4 He
Journal of Physics: Conference Series, 2009
Solid 4 He is viewed as a nearly perfect Debye solid. Yet, recent calorimetry measurements by the PSU group (J. Low Temp. Phys. 138, 853 (2005) and Nature 449, 1025 ) indicate that at low temperatures the specific heat has both cubic and linear contributions. These features appear in the same temperature range where measurements of the torsional oscillator period suggest a supersolid transition. We analyze the specific heat and compare the measured with the estimated entropy for a proposed supersolid transition with 1% superfluid fraction and find that the observed entropy is too small. We suggest that the low-temperature linear term in the specific heat is due to a glassy state that develops at low temperatures and is caused by a distribution of tunneling systems in the crystal. We propose that dislocation related defects produce those tunneling systems. Further, we argue that the reported putative mass decoupling, that means an increase in the oscillator frequency, is consistent with a glass-like transition. The glass scenario offers an alternative interpretation of the torsional oscillator experiments in contrast to the supersolid scenario of nonclassical rotational inertia.
A glassy counterpart to supersolids A Viewpoint on: Theory of the superglass phase
Glasses are liquids that have ceased to flow on experimentally measurable time scales. By constrast, superfluids flow without any resistance. The existence of a phase characterized by simultaneous glassiness and superfluidity may seem like a clear contradiction. However, in a paper in Physical Review B, Giulio Biroli (Institut de Physique Théorique, France), Claudio Chamon (Boston University), and Francesco Zamponi (École Normale Supérieure, France) prove that this is not so [1] and illustrate theoretically the possibility of a "superglass" phase. This phase forms an intriguing amorphous counterpart to the "supersolid" phase [2, 3] that has seen a surge of interest in recent years . Within a "supersolid" phase, superfluidity can occur without disrupting crystalline order.
Physical review letters, 2005
We prove that the necessary condition for a solid to be also a superfluid is to have zero-point vacancies, or interstitial atoms, or both, as an integral part of the ground state. As a consequence, in the absence of symmetry between vacancies and interstitials, superfluidity has a zero probability to occur in commensurate solids which break continuous translation symmetry. We discuss recent 4He experiments by Kim and Chan in the context of this theorem, question its bulk supersolid interpretation, and offer an alternative explanation in terms of superfluid interfaces.