Microscopic molecular superfluid response: theory and simulations

Zeng, Tao; Roy, Pierre‐Nicholas

doi:10.1088/0034-4885/77/4/046601

Cited by 67 publications

(53 citation statements)

References 341 publications

(601 reference statements)

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“…The idea is that the chirp-up physically corresponds to helium density gradually decoupling from the rotor as it speeds up to its terminal velocity; the superfluid fraction of the centrifugally stretched helium increases due to a decrease in the confining effects of the rotor, 84 and this superfluid fraction cannot couple to rotation. 85 Of particular interest is the angular inverse of β, which corresponds to the response time of the fluid (τ R ). The response time of the fluid with respect to the increase in rotational frequency from J = 0 to 1 is determined to be 1.4 ns, which is 0.5 ns slower than that in going from J = 1 to 2.…”

Section: Line Profile Analysismentioning

confidence: 99%

Single and double resonance spectroscopy of methanol embedded in superfluid helium nanodroplets

Douberly

Jäger

2014

The Journal of Chemical Physics

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Methanol is one of the simplest molecules that undergo torsional oscillations, and so it has been extensively studied in the gas phase by various spectroscopic techniques. At 300 K, a large number of rotational, torsional, and vibrational energy levels is populated, and this makes for a rather complicated spectrum, which is still not fully understood. It is expected that in going from 300 K to 0.4 K (the temperature of helium nanodroplets) the population distribution of methanol will mainly collapse into two states; the JK = 00 state for the A1 nuclear spin symmetry species (with ICH3 = 3/2), and the JK = 1-1 state for the E species (ICH3 = 1/2). This results in a simplified spectrum that consists of narrow a-type (ΔK = 0) lines and broader b- and c-type (ΔK = ±1) lines. We have recorded the rotovibrational spectrum of CH3OH in the OH stretching, CH3 stretching and bending, CH3 rocking, and CO stretching regions, and have firmly assigned five bands (v1, v2, v3, v7, and v8), and tentatively assigned five others (v9, 2v4, v4 + v10, 2v10, and v4 + v5). To our knowledge, the transitions we have assigned within the v4 + v10, 2v10, and v4 + v5 bands have not yet been assigned in the gas phase, and we hope that considering the very small "matrix" shift in helium nanodroplets (<1 cm(-1) for most subband origins of CH3OH), those made here can aid in their gas phase identification. Microwave-infrared double resonance spectroscopy was used to confirm the initially tentative a-type infrared assignments in the OH stretching (v1) band of A1 species methanol, in addition to revealing "warm" b-type lines. From a rotovibrational analysis, the B rotational constant is found to be reduced quite significantly (56%) with respect to the gas phase, and the torsional tunneling splittings are relatively unaffected and are at most reduced by 16%. While most rovibrational peaks are Lorentzian shaped, and those which are significantly perturbed by vibrational coupling in the gas phase are additionally broadened, the narrowest ΔJ = +1 peaks are asymmetric, and a skew-type analysis suggests that the response time of the helium solvent upon excitation is of the order of 1 ns.

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Section: Line Profile Analysismentioning

confidence: 99%

Single and double resonance spectroscopy of methanol embedded in superfluid helium nanodroplets

Douberly

Jäger

2014

The Journal of Chemical Physics

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“…Small para-hydrogen clusters are likely superfluid, 1 although no definite conclusion has been experimentally drawn yet. 2 Together with the frictionless displacement of impurities at velocities below the Landau critical velocity, 3 the appearance of quantized vortices is the recognized hallmark of superfluidity in liquid 4 He 4,5 that appear at temperatures below 2.17 K, the superfluid transition temperature.…”

Section: Introductionmentioning

confidence: 99%

Vortex arrays in a rotating superfluidHe4nanocylinder

2014

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Within Density Functional theory, we investigate stationary many-vortex structures in a rotating 4 He nanocylinder at zero temperature. We compute the stability diagram and compare our results with the classical model of vortical lines in an inviscid and incompressible fluid. Scaling the results to millimeter-size buckets, they can be compared with experiments on vortex arrays conducted in the past. Motivated by recent experiments that have used atomic impurities as a means of visualizing vortices in superfluid 4 He droplets, we have also considered the formation of chains of xenon atoms along a vortex line and the interaction between xenon atoms inside the same vortex and on different neighboring vortex lines.PACS numbers: 67.25. D-, 67.25.dk

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“…This quantum character of condensed pH 2 and oD 2 has led to the prediction of a variety of intriguing effects specific to the hydrogen liquids such as superfluidity of pH 2 [10], for which there is so far only indirect evidence coming from spectroscopic studies of small doped pH 2 clusters (see, e.g., Ref. [22], and references therein), or the realization of a structural quantum glass in a supercooled pH 2 -oD 2 mixture [12]. …”

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Observation of crystallization slowdown in supercooled parahydrogen and orthodeuterium quantum liquid mixtures

et al. 2014

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We report a quantitative experimental study of the crystallization kinetics of supercooled quantum liquid mixtures of parahydrogen (pH 2 ) and orthodeuterium (oD 2 ) by high spatial resolution Raman spectroscopy of liquid microjets. We show that in a wide range of compositions the crystallization rate of the isotopic mixtures is significantly reduced with respect to that of the pure substances. To clarify this behavior we have performed path-integral simulations of the nonequilibrium pH 2 -oD 2 liquid mixtures, revealing that differences in quantum delocalization between the two isotopic species translate into different effective particle sizes. Our results provide experimental evidence for crystallization slowdown of quantum origin, offering a benchmark for theoretical studies of quantum behavior in supercooled liquids. Understanding the stability of supercooled liquids with respect to crystallization is a fundamental open problem in condensed matter physics [1]. In this regard, since crystallization competes with glass formation, a knowledge of the mechanisms that govern the crystal growth in supercooled liquids is considered an important step to elucidate the nature of the glass transition [2-6]. So far, experimental studies aiming at providing microscopic insights into the dynamics and crystallization of supercooled liquids have been largely based on the use of colloidal suspensions [7,8], where the large particle size allows one to follow the crystal growth on the laboratory time scale. However, diverse drawbacks such as polydispersity and sedimentation often make the experimental data from these systems difficult to interpret [8,9]. Accessing the details of the crystallization process in simple atomic and molecular counterparts, on the other hand, remains an experimental challenge due to relevant time scales that are orders of magnitude shorter.Theoretical studies have shown that the inclusion of quantum effects adds a further degree of complexity in the behavior of supercooled liquids, leading to novel exotic phenomena such as superfluidity [10,11] or enhanced dynamical slowing down [12][13][14]. Yet again, the difficulties in supercooling a quantum liquid to very low temperatures have so far precluded possible experimental studies of the interplay of quantum effects and structural transformations in nonequilibrium bulk liquids. Here we address these challenges reporting on the experimental investigation of the crystallization kinetics of supercooled liquid mixtures of the isotopic species pH 2 and oD 2 , showing that their quantum nature has a profound impact on the crystallization process.* grisenti@atom.uni-frankfurt.de Binary liquid mixtures exhibit, in general, properties that differ fundamentally from their corresponding pure substances, and mixing a few components is, in particular, a common strategy to hinder crystallization. Indeed, classical binary systems of particles that interact via a simple LennardJones (LJ) pair potential have been widely employed as the simplest theoretical models to inve...

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Microscopic molecular superfluid response: theory and simulations

Cited by 67 publications

References 341 publications

Single and double resonance spectroscopy of methanol embedded in superfluid helium nanodroplets

Single and double resonance spectroscopy of methanol embedded in superfluid helium nanodroplets

Vortex arrays in a rotating superfluidHe4nanocylinder

Observation of crystallization slowdown in supercooled parahydrogen and orthodeuterium quantum liquid mixtures

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