Abstract
The rare-earth hexaboride SmB6, known as the topological Kondo insulator, has attracted tremendous attention in recent years. It was revealed that the topological phase of SmB6 is insensitive to the value of on-site Coulomb interactions (Hubbard U), indicating that the topological phase in SmB6 is robust against strong correlations. On the contrary, the isostructural YbB6 displays a sensitivity to the Hubbard U value. As U increases, YbB6 transforms from topological Kondo insulator to trivial insulator, showing the weak robustness of the topological phase of YbB6 against U. Consequently, the dependence of the topological phase on Hubbard U is a crucial issue in the rare-earth hexaboride family. In this work, we investigate the structural and electronic properties of rare-earth hexaboride compounds through first-principles calculations based on density functional theory. By taking the strong correlations into consideration using a wide range of on-site U values, we study the evolution of the topological phases in rare-earth hexaboride (XB6, X = La, Ce, Pr, Nd, Pm, Sm, Eu). Unlike YbB6, the topological trends in all the examples of XB6 studied in this work are insensitive to the U values. We conclude that in addition to the well-known SmB6, PmB6, NdB6 and EuB6 are also topologically nontrivial compounds, whereas LaB6, CeB6 and PrB6 are topologically trivial metal.
Highlights
The discovery of the topological phase in condensed matter paved the way to classify electronic states [1,2]
Topological insulators have been attracting world-wide extensive attention in recent research [3,4,5,6]
We thenWe perform field electronic are fully optimized through first-principles calculations
Summary
The discovery of the topological phase in condensed matter paved the way to classify electronic states [1,2]. Three dimensional materials with time reversal symmetry and inversion symmetry may harbor a topologically nontrivial phase if a band gap and band inversion emerge owing to spin–orbit interaction (SOI) [7]. [1], [1], the gap semiconductor the topological phase of YbB is sensitive to the Hubbard. Kondo insulator to trivial insulator, showing the weak of the topological phase of from topological. Kondo insulator to trivial insulator, showing therobustness weak robustness of the topological. Ce, Ce, Pr, Nd, Pm, Pm, Sm, Sm, Eu) Eu) are Inthis thisstudy, study,the thelattice lattice structures rare-earth hexaboride. We thenWe perform field electronic are fully optimized through first-principles calculations. Phases, we analyze if SOI electroniccalculations structure calculations with andSOI. Tothe reveal the topological we analyze would upopen a continuous energy gap at thegap.
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