Atomically Layered Helium Films at Ultralow Temperatures: Model Systems for Realizing Quantum Materials

Saunders, J.; Cowan, Brian; Nyéki, J.

doi:10.1007/s10909-020-02448-9

Cited by 9 publications

(5 citation statements)

References 133 publications

(184 reference statements)

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“…Despite possible signatures from recent STM works [53,54], the observation of this long-sought PDW state has been hindered by the intrinsic complexity of strongly correlated systems. The exotic superfluid phases observed here and the recent searches for the PDW state in 3 He [55,56] imply that low-dimensional helium can provide excellent experimental platforms to realize novel quantum many-body phenomena for both bosons ( 4 He) and fermions ( 3 He), benefiting from their extremely pristine quality and reduced complexity [57]. In summary, our rigid two-frequency TO study of 4 He films on graphite provides unequivocal evidence of the superfluid phase in the second layer, confined to a coverage range of 17∼18.8 atoms/nm 2 .…”

mentioning

confidence: 85%

Spatially Modulated Superfluid State in Two-Dimensional $^4$He Films

Choi,

Zadorozhko,

Choi

et al. 2021

Preprint

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The second layer of 4 He films adsorbed on a graphite substrate is an excellent experimental platform to study the interplay between superfluid and structural orders. Here, we report a rigid twofrequency torsional oscillator study on the second layer as a function of temperature and 4 He atomic density. We find that the superfluid density is independent of frequency, which can be interpreted as unequivocal evidence of genuine superfluidity. The phase diagram established in this work reveals that a superfluid phase coexists with hexatic density-wave correlation and a registered solid phase. This suggests the second layer as a candidate for hosting two exotic quantum ground states: the spatially modulated superfluid and supersolid phases, resulting from the interplay between superfluid and structural orders.

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mentioning

confidence: 85%

Spatially Modulated Superfluid State in Two-Dimensional $^4$He Films

Choi,

Zadorozhko,

Choi

et al. 2021

Preprint

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“…This mismatch ensures a finite amount of defects/vacancies in adsorbed solid helium even at zero temperature, i.e., so-called zero-point vacancies, which give their hallmark on the ground state, and which have not yet been ever found in the bulk 3D crystals. In the planar geometry of graphite/grafoil where carbon atoms are assembled into a hexagonal lattice, the famous 1/3 (every third carbon hexagon is occupied by helium atom) commensurate solid phase is very well established 13 – 17 . Another commensurate phase 18 is stabilized at densities corresponding to the dimer 2/5 solid suggested by Greywall 19 .…”

Section: Introductionmentioning

confidence: 99%

Topologically-imposed vacancies and mobile solid 3He on carbon nanotube

et al. 2022

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Low dimensional fermionic quantum systems are exceptionally interesting because they reveal distinctive physical phenomena, including among others, topologically protected excitations, edge states, frustration, and fractionalization. Our aim was to confine 3He on a suspended carbon nanotube to form 2-dimensional Fermi-system. Here we report our measurements of the mechanical resonance of the nanotube with adsorbed sub-monolayer down to 10 mK. At intermediate coverages we have observed the famous 1/3 commensurate solid. However, at larger monolayer densities we have observed a quantum phase transition from 1/3 solid to an unknown, soft, and mobile solid phase. We interpret this mobile solid phase as a bosonic commensurate crystal consisting of helium dimers with topologically-induced zero-point vacancies which are delocalized at low temperatures. We thus demonstrate that 3He on a nanotube merges both fermionic and bosonic phenomena, with a quantum phase transition between fermionic solid 1/3 phase and the observed bosonic dimer solid.

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“…Adsorbed helium films on graphite are a unique system for studying two dimensional (2D) quantum phenomena [1,2]. This system has a rich variety of two isotopes ( 3 He and 4 He, corresponding to fermions and bosons, respectively), different numbers of atomic layers, and various condensed states such as 2D gas, fluid, and commensurate and incommensurate solids.…”

Section: Introductionmentioning

confidence: 99%

Structural Study of Adsorbed Helium Films: New Approach with Synchrotron Radiation X-rays

Yamaguchi,

Tajiri,

Kumashita

et al. 2021

Preprint

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A few atomic layers of helium adsorbed on graphite have been attracting much attention as one of the ideal quantum systems in two dimension. Although previous reports on neutron diffraction have shown fundamental structural information in these systems, there still remain many open questions. Here, we propose surface crystal truncation rod (CTR) scatterings using synchrotron radiation X-rays as a promising method to reveal surface and interface structures of helium films on graphite at temperatures below 2 K, based on the preliminary Structural Study of Adsorbed Helium Films experimental results on a monolayer of 4 He on a thin graphite. Our estimation on heat generation by X-ray irradiations also suggests that CTR scatterings are applicable to even at system temperatures near 100 mK.

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Atomically Layered Helium Films at Ultralow Temperatures: Model Systems for Realizing Quantum Materials

Abstract: This year is also the 50th anniversary of the discovery of exfoliated graphite as a particularly uniform substrate (Thomy and Duval in

Cited by 9 publications

References 133 publications

Spatially Modulated Superfluid State in Two-Dimensional $^4$He Films

Spatially Modulated Superfluid State in Two-Dimensional $^4$He Films

Topologically-imposed vacancies and mobile solid 3He on carbon nanotube

Structural Study of Adsorbed Helium Films: New Approach with Synchrotron Radiation X-rays

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