Handedness-dependent quasiparticle interference in the two enantiomers of the topological chiral semimetal PdGa

Abstract

It has recently been proposed that combining chirality with topological band theory results in a totally new class of fermions. Understanding how these unconventional quasiparticles propagate and interact remains largely unexplored so far. Here, we use scanning tunneling microscopy to visualize the electronic properties of the prototypical chiral topological semimetal PdGa. We reveal chiral quantum interference patterns of opposite spiraling directions for the two PdGa enantiomers, a direct manifestation of the change of sign of their Chern number. Additionally, we demonstrate that PdGa remains topologically non-trivial over a large energy range, experimentally detecting Fermi arcs in an energy window of more than 1.6 eV that is symmetrically centered around the Fermi level. These results are a consequence of the deep connection between chirality in real and reciprocal space in this class of materials, and, thereby, establish PdGa as an ideal topological chiral semimetal.

Optical Response of Chiral Multifold Semimetal PdGa

“…The lattice parameters were adopted from Ref. [29]. Figure 1 shows the chiral atomic structure and the Fermi surface of PdGa.…”

“…To this end, chiral crystal structures belonging to the RhSi family, space group P2 1 3, number 198, have garnered attention as angle resolved photoemission spectroscopy (ARPES) measurements provided strong indications that these materials host surface states, which are maximally extended in k-space [23][24][25][26][27][28]. The lack of inversion and mirror symmetries, in combination with SOC, leads to the splitting of bands around the high symmetry points Γ and R, giving rise to a non-collinear spin arrangement with Chern numbers χ = ±4 [29] with maximally extended surface states, ranging from the center to the edge of the Brillouin zone [25,27,30]. In such semimetals, the quantized circular photogalvanic effect has been predicted, which, by effect of topological states, constitutes a photocurrent, quantized in units of material-independent fundamental constants [31][32][33][34].…”

Topological Quantum Materials from the Viewpoint of Chemistry

“…164 Later, a very similar crystal growth method was used to grow opposite-enantiomorph single crystals of PdGa, a chiral topological material. 165,166 3.5. Optical floating zone (OFZ)…”

Optical method to detect the relationship between chirality of reciprocal space chiral multifold fermions and real space chiral crystals

“…In addition to the wide separation between opposite topological charges in the momentum space, the absence of mirror symmetry also leads to their large separation in energy space, providing an ideal platform for the study of quantized circular photogalvanic effects (CPGE) [3,5,7,8]. Following their theoretical predictions, long Fermi arcs, high-order degenerated band crossings, and topological CPGE were soon observed in the expected chiral crystals via angle-resolved photoemission spectroscopty (ARPES) [9][10][11][12][13], scanning tunneling microscopy (STM) [14], and optical measurements [15][16][17].…”

“…Recently, based on ARPES and STM measurements, a sign change was detected in the Fermi velocity of surface Fermi arcs in semimetals possessing chiral multifold fermions and crystals of opposite chiralities. This implied a deep relationship between chiral lattices in the real space and chiral fermions in the momentum space [13,14,18]. This relationship offers a degree of freedom to modulate chiral fermions and their corresponding physical properties.…”