arXiv subjects

Firoza Kabir

Publications and source records attributed to Firoza Kabir.

21 records · Page 2Linked to original sources

arXiv2017

Observation of Gapless Dirac Surface States in ZrGeTe

The experimental discovery of the topological Dirac semimetal establishes a platform to search for various exotic quantum phases in real materials. ZrSiS-type materials have recently emerged as topological nodal-line semimetals where gapped Dirac-like surface states are observed. Here, we present a systematic angle-resolved photoemission spectroscopy (ARPES) study of ZrGeTe, a nonsymmorphic symmetry protected Dirac semimetal. We observe two Dirac-like gapless surface states at the same $\bar X$ point of the Brillouin zone. Our theoretical analysis and first-principles calculations reveal that these are protected by crystalline symmetry. Hence, ZrGeTe appears as a rare example of a naturally fine tuned system where the interplay between symmorphic and non-symmorphic symmetry leads to rich phenomenology, and thus opens for opportunities to investigate the physics of Dirac semimetallic and topological insulating phases realized in a single material.

cond-mat.mes-hall↗

arXiv2017

Distinct multiple fermionic states in a single topological metal

Among the quantum materials that gained interest recently are the topological Dirac/Weyl semimetals, where conduction and valence bands touch at points in reciprocal (k)-space, and the Dirac nodal-line semimetals, where these bands touch along a line or a loop in k-space. However, the coexistence of multiple fermion phases in one and the same material has not been verified yet. Using angle-resolved photoemission spectroscopy (ARPES) and first-principles electronic structure calculations, we systematically study the metallic topological quantum material, Hf2Te2P. Our investigations discover various properties that are rare and never observed in a single Dirac material. We observe the coexistence of both weak and strong topological surface states in the same material and interestingly, at the same momentum position. An one-dimensional Dirac crossing{the Dirac-node arc-along a high-symmetry direction is revealed by our first-principles calculations and confirmed by our ARPES measurements. This novel state is associated with the surface bands of a weak topological insulator protected by in-plane time-reversal invariance. Ternary compound Hf2Te2P thus emerges as an intriguing platform to study the coexistence and competition of multi-fermionic states in one material.

cond-mat.mes-hall↗

arXiv2017

Observation of topological nodal-line fermionic phase in GdSbTe

Topological Dirac semimetals with accidental band touching between conduction and valence bands protected by time reversal and inversion symmetry are at the frontier of modern condensed matter research. Theoretically one can get Weyl and/or nodal-line semimetals by breaking either one of them. Most of the discovered topological semimetals are nonmagnetic i.e respect time reversal symmetry. Here we report the experimental observation of a topological nodal-line semi metallic state in GdSbTe using angle-resolved photoemission spectroscopy. Our systematic study reveals the detailed electronic structure of the paramagnetic state of GdSbTe. We observe the presence of multiple Fermi surface pockets including a diamond-shape, an elliptical shape, and small circular pockets around the zone center and high symmetry M and X points of the Brillouin zone (BZ), respectively. Furthermore, we observe the presence of a Dirac-like state at the X point of the BZ. Interestingly, our experimental data shows a robust Dirac like state both below and above the magnetic transition temperature (T_N ~ 13 K). Having relatively higher transition temperature, GdSbTe provides an archetype platform to study the interaction between magnetism and topological states of matter.

cond-mat.mes-hall↗