Towards ideal topological materials: Comprehensive database searches using symmetry indicators

Abstract

Topological materials (TMs) showcase intriguing physical properties defying expectations based on conventional materials, and hold promise for the development of devices with new functionalities. While several theoretically proposed TMs have been experimentally confirmed, extensive experimental exploration of topological properties as well as applications in realistic devices have been held back due to the lack of excellent TMs in which interference from trivial Fermi surface states are minimized. We tackle this problem in the present work by applying our recently developed method of symmetry indicators to all non-magnetic compounds in the 230 space groups. An exhaustive database search reveals thousands of TM candidates. Of these, we highlight the excellent TMs, the 258 topological insulators and 165 topological crystalline insulators which have either noticeable full band gap or a considerable direct gap together with small trivial Fermi pockets. We also give a list of 489 topological semimetals with the band crossing points located near the Fermi level. All predictions obtained through standard generalized gradient approximation (GGA) calculations were cross-checked with the modified Becke-Johnson (MBJ) potential calculations, appropriate for narrow gap materials. With the electronic and optical behavior around the Fermi level dominated by the topologically non-trivial bands, these newly found TMs candidates open wide possibilities for realizing the promise of TMs in next-generation electronic devices.

A New Magnetic Topological Quantum Material Candidate by Design

“…Theorists have scoured the ICSD for previously reported materials that can display topological electronic properties, but the design of totally new topological quantum materials remains rare, especially for cases where the interactions of different quantum states is expected. [11][12][13][14][15][16] Located at the Zintl border in the periodic table, the element Sn has moderate electronegativity, thus allowing it to participate in various types of bonding interactions. This provides flexibility in tuning the electronic properties of materials in which the electronic states of tin are dominant.…”

Multifold nodal points in magnetic materials

“…The prediction and observation of Weyl [1][2][3][4][5][6][7][8] and Dirac [9][10][11][12][13] fermions catalyzed an intense theoretical and experimental search for topological nodal semimetals in condensed matter systems. [14][15][16][17][18][19][20][21] These systems provide a solid state realization of the chiral 8,22 and gravitational anomalies 23,24 and exhibit many novel physical properties, such as gapless Fermi arc surface states, 1 extremely large magnetoresistance, 25 and giant nonlinear optical response. 26,27 Topological semimetals also illustrate the interplay between symmetry and topology: Weyl fermions can exist without any symmetry, but are forbidden by the combination of time reversal and inversion symmetry.…”

Unified understanding of symmetry indicators for all internal symmetry classes

“…Recently, this type of relations between the band topology and the symmetry representations in the band structure are further investigated and extended to wider class of spatial symmetries, i.e., 230 space groups [21][22][23] and 1651 magnetic space groups [24], and to more general class of band topology including HOTIs [25][26][27]. The generalized Fu-Kane formula, dubbed as "symmetry indicator" of band topology, significantly reduces the effort of computing the topological indices and thus should be useful in the actual material search [28][29][30][31].…”