Visualizing Dirac nodal-line band structure of topological semimetal ZrGeSe by ARPES

Zhengwang Cheng,Fangsen Li,Xin Zhang,Yan Cao,Zhijun Wang,Shaojian Li,Zhibin Shao,Jiagui Feng,Hui Yuan,Zhiqiang Mao,Haigen Sun,Qi Bian,Minghu Pan,Zongyuan Zhang,Sunan Ding

doi:10.1063/1.5084090

Abstract

As a member of ZrHM (H = Si/Ge/Sn; M = O/S/Se/Te) family materials, which were predicted to be the candidates of topological Dirac nodal-line semimetals, ZrGeSe exhibited particular properties, such as magnetic breakdown effect in the transport measurement, different from its other isostructural compounds, informing an unique topology of the electronic band structure. However, the related experimental research is insufficient until now. Here, we present a systematic study of the band structure and Fermi surfaces (FS) of ZrGeSe by angle-resolved photoemission spectroscopy (ARPES). Our Brillouin zone (BZ) mapping shows multiple Fermi pockets such as the diamond-shaped FS around the zone center Γ point, small electron pocket encircling the X point of the BZ, and lenses-shaped FS in the Γ-M direction. The obtained Fermi velocities and effective masses were up to 9.2 eV·Å and 0.42 me, and revealing an anisotropic electronic property along different high-symmetry k-space directions. Moreover, a kink appears near the Fermi level in the linear Dirac bands along the M-X direction, probably originated from the band hybridization and has not been reported in other ZrHM-type materials. Our findings support that the ZrHM-type material family can be a new platform on which to explore exotic states of quantum matter.

Highlights

INTRODUCTIONTopological phases of matter in condensed matter physics can be broadly classified into two major classes. The first one has gapped bulks and gapless conducting modes on their surfaces or boundaries, including topological insulators (TIs), topological superconductors, and other symmetry-protected topological phases. In the second class of topological matters, the bulk gap closes at certain points or lines in the Brillouin zone (BZ) through momentum-space nondegenerate touching of conduction and valence bands, correspond to topological nodal-point (Weyltype or Dirac-type)/nodal-line semimetals, respectively
With the influence of spin-orbit coupling (SOC), a gap will open along the node lines, leading to the two-dimensional (2D) topological insulator (TI) being predicted in the monolayer ZrHM,11,12 which was experimentally realized in a few artificial systems such as InAs/GaSb13 and HgTe/(Hg,Cd)Te14 quantum wells
ZrGeSe was the only material that magnetic breakdown (MB) effect was observed in the de Haas–van Alphen (dHvA)/Shubnikov–de Haas (SdH) oscillations under

Summary

INTRODUCTION

Topological phases of matter in condensed matter physics can be broadly classified into two major classes. The first one has gapped bulks and gapless conducting modes on their surfaces or boundaries, including topological insulators (TIs), topological superconductors, and other symmetry-protected topological phases. In the second class of topological matters, the bulk gap closes at certain points or lines in the Brillouin zone (BZ) through momentum-space nondegenerate touching of conduction and valence bands, correspond to topological nodal-point (Weyltype or Dirac-type)/nodal-line semimetals, respectively.. The family of materials ZrHM (H = Si/Ge/Sn; M = O/S/Se/Te) with the PbFCl-type structure were predicted to be the candidates of topological Dirac nodal-line semimetals.. Light effective mass, high mobility, and nontrivial Berry phase had been revealed through dHvA/SdH oscillations in ZrSiS, ZrSiSe, ZrSiTe, ZrGeM (M = S/Se/Te), and ZrSnTe, diamond-like FS with Dirac-type nodal line were observed in ARPES characterizations in ZrSiS, ZrSiSe, ZrSiTe, ZrGeTe, and ZrSnTe.. ZrGeSe was the only material that magnetic breakdown (MB) effect was observed in the dHvA/SdH oscillations under

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSION