Commensurability oscillations in a lateral superlattice with broken inversion symmetry

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.

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Phase transformation and Raman spectra in BaTiO3 nanocrystals

MRS Proceedings ◽

10.1557/proc-718-d10.7 ◽

2002 ◽

Vol 718 ◽

Cited By ~ 4

Author(s):

Jian Yu ◽

X. J. Meng ◽

J.L. Sun ◽

G.S. Wang ◽

J.H. Chu

Keyword(s):

Particle Size ◽

Phase Transformation ◽

Low Temperature ◽

Long Range ◽

Lattice Expansion ◽

Inversion Symmetry ◽

Range Interaction ◽

Cooperative Phenomena ◽

Long Range Interaction ◽

Hydrothermal Methods

AbstractIn this paper, size-induced ferroelectricit yweakening, phase transformation, and anomalous lattice expansion are observed in nanocrystalline BaTiO3 (nc-BaTiO3) deriv ed b y low temperature hydrothermal methods, and they are w ellunderstood using the terms of the long-range interaction and its cooperative phenomena altered by particle size in covalen t ionic nanocrystals. In cubic nc-BaTiO3, five modes centerd at 186, 254, 308, 512 and 716 cm-1 are observed Raman active in cubic nanophase, and they are attributed to local rhombohedral distortion breaking inversion-symmetry in cubic nanophase. The254 and 308 cm-1 modes are significantly affected not only by the concentration of hydroxyl defects, but also their particular configuration. And the 806 cm-1 modes found to be closely associated with OH - absorbed on grain boundaries.

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Dzyaloshinskii–Moriya interaction in noncentrosymmetric superlattices

npj Computational Materials ◽

10.1038/s41524-021-00592-8 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Woo Seung Ham ◽

Abdul-Muizz Pradipto ◽

Kay Yakushiji ◽

Kwangsu Kim ◽

Sonny H. Rhim ◽

...

Keyword(s):

Heavy Metal ◽

Degrees Of Freedom ◽

Orbit Coupling ◽

Inversion Symmetry ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Band Formation ◽

Research Activities ◽

Moriya Interaction

AbstractDzyaloshinskii–Moriya interaction (DMI) is considered as one of the most important energies for specific chiral textures such as magnetic skyrmions. The keys of generating DMI are the absence of structural inversion symmetry and exchange energy with spin–orbit coupling. Therefore, a vast majority of research activities about DMI are mainly limited to heavy metal/ferromagnet bilayer systems, only focusing on their interfaces. Here, we report an asymmetric band formation in a superlattices (SL) which arises from inversion symmetry breaking in stacking order of atomic layers, implying the role of bulk-like contribution. Such bulk DMI is more than 300% larger than simple sum of interfacial contribution. Moreover, the asymmetric band is largely affected by strong spin–orbit coupling, showing crucial role of a heavy metal even in the non-interfacial origin of DMI. Our work provides more degrees of freedom to design chiral magnets for spintronics applications.

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Topological phase transition between a normal insulator and a topological metal state in a quasi-one-dimensional system

Scientific Reports ◽

10.1038/s41598-021-92390-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Milad Jangjan ◽

Mir Vahid Hosseini

Keyword(s):

Phase Transition ◽

Dimensional System ◽

Inversion Symmetry ◽

Topological Phase ◽

Edge States ◽

Zero Energy ◽

One Dimensional ◽

Topological Phase Transition ◽

Metal State ◽

Topological Metal

AbstractWe theoretically report the finding of a new kind of topological phase transition between a normal insulator and a topological metal state where the closing-reopening of bandgap is accompanied by passing the Fermi level through an additional band. The resulting nontrivial topological metal phase is characterized by stable zero-energy localized edge states that exist within the full gapless bulk states. Such states living on a quasi-one-dimensional system with three sublattices per unit cell are protected by hidden inversion symmetry. While other required symmetries such as chiral, particle-hole, or full inversion symmetry are absent in the system.

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