A1 Journal article (refereed), original research

Quasiperiodic ordering in thick Sn layer on i-Al-Pd-Mn: A possible quasicrystalline clathrate

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Publication Details
Authors: Singh Vipin Kumar, Mihalkovic Marek, Krajčí Marian, Sarkar Shuvam, Sadhukhan Pampa, Maniraj M., Rai Abhishek, Pussi Katariina, Schlagel Deborah L., Lograsso Thomas A., Shukla Ajay Kumar, Barman Sudipta Roy
Publication year: 2020
Language: English
Related Journal or Series Information: Physical Review Research
Volume number: 2
Issue number: 1
eISSN: 2643-1564
JUFO-Level of this publication: 1
Open Access: Open Access publication
Location of the parallel saved publication: https://arxiv.org/abs/1704.06783


Realization of an elemental solid-state quasicrystal has remained a
distant dream so far in spite of extensive work in this direction for
almost two decades. In the present work, we report the discovery of
quasiperiodic ordering in a thick layer of elemental Sn grown on
icosahedral (i)-Al-Pd-Mn.
The scanning tunneling microscopy (STM) images and the low-energy
electron diffraction patterns of the Sn layer show specific structural
signatures that portray quasiperiodicity but are distinct from the
substrate. Photoemission spectroscopy reveals the existence of the
pseudogap around the Fermi energy up to the maximal Sn thickness. The
structure of the Sn layer is modeled as a form of quasicrystalline
clathrate on the basis of multiple supporting evidences: First, from ab initio total energy evaluation, the energy of bulk Sn clathrate quasicrystal is lower than the high-temperature metallic β-Sn phase, but higher than the low-temperature α-Sn phase. A comparative study of the free slab energetics shows that surface energy favors clathrate over α-Sn up to about 4-nm layer thickness and matches β-Sn
for narrow window of slab thickness of 2–3 nm. Second, the bulk
clathrate exhibits gap opening near Fermi energy, while the free slab
form exhibits a pronounced pseudogap, which explains the pseudogap
observed in photoemission. Third, the STM images exhibit good agreement
with clathrate model. Finally, we establish the adlayer-substrate
compatibility based on very similar (within 1%) the cage-cage separation
in the Sn clathrate and the pseudo-Mackay cluster-cluster separation on
the i-Al-Pd-Mn
surface. Furthermore, the nucleation centers of the Sn adlayer on the
substrate are identified and these are shown to be a valid part of the
Sn clathrate structure. Thus, based on both experimental and ab initio density functional theory calculations, we propose that 4-nm-thick Sn adlayer deposited on fivefold surface of i-Al-Pd-Mn substrate is in fact a metastable realization of elemental, clathrate family quasicrystal.

Last updated on 2020-30-06 at 11:42