Monolayer RhB4: half-auxeticity and almost ideal spin-orbit Dirac point semimetal
Structural-property relationship, the connection between materials' structures and their properties, is central to the materials research. Especially at reduced dimensions, novel structural motifs often generate unique physical properties.Motivated by a recent work reporting a novel half auxeti...
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Main Authors: | , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
2023
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Subjects: | |
Online Access: | https://hdl.handle.net/10356/164301 |
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Institution: | Nanyang Technological University |
Language: | English |
Summary: | Structural-property relationship, the connection between materials' structures and their properties, is central to the materials research. Especially at reduced dimensions, novel structural motifs often generate unique physical properties.Motivated by a recent work reporting a novel half auxetic effect in monolayer PdB4 with a hypercoordinated structure, here, we
extensively explore similar 2D transition metal boride structures MB4 with M
covering 3d and 4d elements.Our investigation screens out one stable candidate,
the monolayer RhB4. We find that monolayer RhB4 also shows half auxeticity,
i.e., the material always expands in a lateral in-plane direction in response
to an applied strain in the other direction, regardless of whether the strain
is positive or negative.We show that this special mechanical character is
intimately tied to the hypercoordinated structure with the M\c{opyright}B8
structural motif. Furthermore, regarding electronic properties, monolayer RhB4
is found to be the first example of an almost ideal 2D spin-orbit Dirac point
semimetal.The low-energy band structure is clean, with a pair of fourfold
degenerate Dirac points robust under spin-orbit coupling located close to the
Fermi level. These Dirac points are enforced by the nonsymmorphic space group
symmetry which is also determined by the lattice structure. Our work deepens
the fundamental understanding of structural-property relationship in reduced
dimensions. The half auxeticity and the spin-orbit Dirac points will make
monolayer RhB4 a promising platform for nanomechanics and nanoelectronics
applications. |
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