Rotational fluctuation of molecules in quantum clusters. II. Molecular rotation and superfluidity in OCS-doped helium-4 clusters

Miura, S.

doi:10.1063/1.2713397

Cited by 29 publications

(23 citation statements)

References 37 publications

(45 reference statements)

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“…Systematic analysis on the molecular rotational fluctuation of the OCS͑ 4 He͒ N is presented in the companion paper II. 12 In the following, we discuss the techniques developed in the present study.…”

Section: Discussionmentioning

confidence: 99%

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Rotational fluctuation of molecules in quantum clusters. I. Path integral hybrid Monte Carlo algorithm

Miura

2007

The Journal of Chemical Physics

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In this paper, we present a path integral hybrid Monte Carlo ͑PIHMC͒ method for rotating molecules in quantum fluids. This is an extension of our PIHMC for correlated Bose fluids ͓S. Miura and J. Tanaka, J. Chem. Phys. 120, 2160 ͑2004͔͒ to handle the molecular rotation quantum mechanically. A novel technique referred to be an effective potential of quantum rotation is introduced to incorporate the rotational degree of freedom in the path integral molecular dynamics or hybrid Monte Carlo algorithm. For a permutation move to satisfy Bose statistics, we devise a multilevel Metropolis method combined with a configurational-bias technique for efficiently sampling the permutation and the associated atomic coordinates. Then, we have applied the PIHMC to a helium-4 cluster doped with a carbonyl sulfide molecule. The effects of the quantum rotation on the solvation structure and energetics were examined. Translational and rotational fluctuations of the dopant in the superfluid cluster were also analyzed.

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Section: Discussionmentioning

confidence: 99%

“…56 The small ͑but non-negligible͒ discrepancy between the present calculation and the experimental nanodroplet value will be discussed in the companion paper II. 12 In Fig. 4, we show a free-rotor correlation function using the estimated B eff .…”

Section: -7mentioning

confidence: 99%

Rotational fluctuation of molecules in quantum clusters. I. Path integral hybrid Monte Carlo algorithm

Miura

2007

The Journal of Chemical Physics

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“…It is important to note that the angulon quasiparticle theory described below is substantially simpler -and therefore more transparent -than numerical calculations based on Monte-Carlo algorithms [52,[54][55][56][57][58][69][70][71][72][73][74][75][76][77][78][79].…”

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confidence: 99%

Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules

Cherepanov

Lemeshko

2017

Phys. Rev. Materials

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The formation of vortices is usually considered to be the main mechanism of angular momentum disposal in superfluids. Recently, it was predicted that a superfluid can acquire angular momentum via an alternative, microscopic route -namely, through interaction with rotating impurities, forming so-called 'angulon quasiparticles ' [Phys. Rev. Lett. 114, 203001 (2015)]. The angulon instabilities correspond to transfer of a small number of angular momentum quanta from the impurity to the superfluid, as opposed to vortex instabilities, where angular momentum is quantized in units of per atom. Furthermore, since conventional impurities (such as molecules) represent three-dimensional (3D) rotors, the angular momentum transferred is intrinsically 3D as well, as opposed to a merely planar rotation which is inherent to vortices. Herein we show that the angulon theory can explain the anomalous broadening of the spectroscopic lines observed for CH3 and NH3 molecules in superfluid helium nanodroplets, thereby providing a fingerprint of the emerging angulon instabilities in experiment.One of the distinct features of the superfluid phase is the formation of vortices -topological defects carrying quantized angular momentum, which arise if the bulk of the superfluid rotates faster than some critical angular velocity [1,2]. Vortex nucleation has been considered to be the main mechanism angular momentum disposal in superfluids [1][2][3][4][5]. Recently, it was predicted that a superfluid can acquire angular momentum via a different, microscopic route, which takes effect in the presence of rotating impurities, such as molecules [6][7][8][9][10][11][12][13]. In particular, it was demonstrated that a rotating impurity immersed in a superfluid forms the 'angulon' quasiparticle, which can be thought of as a rigid rotor dressed by a cloud of superfluid excitations carrying angular momentum [14-21].The angulon theory was able to describe, in good agreement with experiment, renormalization of rotational constants [22,23] and laser-induced dynamics [24,25] of molecules in superfluid helium nanodroplets. One of the key predictions of the angulon theory are the socalled 'angulon instabilities ' [14-16] that occur at some critical value of the molecule-superfluid coupling where the angulon quasiparticle becomes unstable and one or a few quanta of angular momentum are resonantly transferred from the impurity to the superfluid. These instabilities are fundamentally different from the vortex instabilities, associated with the transfer of angular momentum quantised in units of per atom of the superfluid. Furthermore, vortices can be thought of as planar rotors, i.e., the eigenstates of theL z operator. Angulons, on the other hand, are the eigenstates of the total angular momentum operator,L 2 , and therefore the transferred angular momentum is three-dimensional. While vortex instabilities have been subject to several experimental studies in the context of superfluid helium [4,5,[26][27][28][29][30][31], ultracold quantum gases [32][33][34][35][36]...

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“…The first similar study of a molecule (SF 6 ) with low resolution infrared spectrum was reported in 1992 [35], followed by its high resolution spectroscopic study in 1995 [4]; the term high resolution spectra refers to rotationally resolved microwave/ infrared spectra. In 1998, Grebenev et al analysed the spectra of a molecule, embedded in as few as 60 He atoms [5].…”

Section: Experimental Studiesmentioning

confidence: 99%

“…represent the effects of quantum mechanics acting on the bulk properties of matter on a large scale and thus, superfluidity is, rightly, termed as macroscopic quantum phenomenon [1]. Recently, however, the high resolution spectroscopy of doped molecules in He nanodroplets (number of He atoms, N ~ 10 3 - 10 4 ) and clusters ( 4 He N -M, M being the embedded molecule and N = 1, 2, ...) [2] provided a unique method to explore superfluidity in such a microscopic system (MICROSCOPIC SUPERFLUIDITY [3]), as well [4][5][6]. It is found that the rotational spectrum of an embedded molecule in liquid He shows sharp peaks, similar to that of the molecule in gaseous state [5,7,8] which indicates that the molecule rotates like a free rotor, although, with an increased moment of inertia (I).…”

Section: Introductionmentioning

confidence: 99%

Quantum dynamics of molecules in 4He nano-droplets: Microscopic superfluidity

et al. 2011

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High resolution spectroscopy of doped molecules in He nano-droplets and clusters gives a signature of superfluidity in microscopic system, termed as microscopic superfluidity. Ro-vibrational spectrum of HeN-M clusters is studied with the help of some important observations, revealed from experiments (viz., localised and orderly arrangement of He atoms, although, being free to move in the order of their locations; individual He atoms can not be tagged as normal/ superfluid, etc.) and other factors (e.g., consideration that the 4 4 4 4 4 He atoms which happen to fall in the plane of rotation of a molecule, render a equipotential ring and thus, do not take part in rotation; etc.) which effect the rotational and vibrational spectrum of the system. This helps us in successfully explaining the experimental findings which state that the rotational spectrum of clusters have sharp peaks (indicating that the molecule rotates like a free rotor) and moment of inertia and vibrational frequency shift have a non-trivial dependence on N.

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Rotational fluctuation of molecules in quantum clusters. II. Molecular rotation and superfluidity in OCS-doped helium-4 clusters

Cited by 29 publications

References 37 publications

Rotational fluctuation of molecules in quantum clusters. I. Path integral hybrid Monte Carlo algorithm

Rotational fluctuation of molecules in quantum clusters. I. Path integral hybrid Monte Carlo algorithm

Fingerprints of angulon instabilities in the spectra of matrix-isolated molecules

Quantum dynamics of molecules in 4He nano-droplets: Microscopic superfluidity

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