Browsing by Author "Jan Minár"

Now showing 1 - 2 of 2

Role of chemical disorder in tuning the Weyl points in vanadium doped Co2TiSn
(American Physical Society, 2021) Payal Chaudhary; Krishna Kant Dubey; Gaurav K. Shukla; Sanjay Singh; Surasree Sadhukhan; Sudipta Kanungo; Ajit K. Jena; S.-C. Lee; S. Bhattacharjee; Jan Minár; Sunil Wilfred D'Souza
The lack of time-reversal symmetry and Weyl fermions give exotic transport properties to Co-based Heusler alloys. In the present study, we have investigated the role of chemical disorder on the variation of Weyl points in Co2Ti1-xVxSn magnetic Weyl semimetal candidate. We employ the first principle approach to track the evolution of the nodal lines responsible for the appearance of Weyl node in Co2TiSn as a function of V substitution in place of Ti. By increasing the V concentration in place of Ti, the nodal line moves toward Fermi level and remains at Fermi level around the middle composition. Further increase of the V content, leads shifting of nodal line away from Fermi level. Density of state calculation shows half-metallic behavior for the entire range of composition. The magnetic moment on each Co atom as a function of V concentration increases linearly up to x=0.4, and after that, it starts decreasing. We also investigated the evolution of the Weyl nodes and Fermi arcs with chemical doping. The first-principles calculations reveal that via replacing almost half of the Ti with V, the intrinsic anomalous Hall conductivity increased twice as compared to the undoped composition. Our results indicate that the composition close to the 50% V doped Co2TiSn will be an ideal composition for the experimental investigation of Weyl physics. © 2021 American Physical Society.
Tuning of nodal line states via chemical alloying in Co2 CrX (X=Ga, Ge) Heusler compounds for a large anomalous Hall effect
(American Physical Society, 2024) Ujjawal Modanwal; Gaurav K. Shukla; Ajit K. Jena; Satadeep Bhattacharjee; Sunil Wilfred D'Souza; Jan Minár; Sanjay Singh
Topological materials have attracted significant interest in condensed matter physics for their unique topological properties leading to potential technological applications. Topological nodal line semimetals, a subclass of topological materials, exhibit symmetry-protected nodal lines, where band crossings occur along closed curves in the three-dimensional Brillouin zone. When the nodal lines are gapped out due to perturbation in the Hamiltonian, a large Berry curvature (BC) arises in the surrounding area of the gapped nodal line, leading to exotic anomalous transport responses. In this paper, we studied the Co2CrX (X=Ga, Ge) Heusler compounds that exhibit mirror symmetry-protected nodal line states below the Fermi level. The BC calculation yields anomalous Hall conductivity (AHC) of about 292 and 217 S/cm for Co2CrX (X=Ga, Ge), respectively, at the Fermi level, which increases by up to 400% at the nodal line energy level. We theoretically analyzed that 20% and 60% zinc (Zn) alloying in Co2CrX (X=Ga, Ge) effectively lowers the Fermi level by 50 meV and 330 meV, respectively, aligning with the protected crossings. Consequently, we identified Co2CrGe0.4Zn0.6 and Co2CrGa0.8Zn0.2 as compositions to achieve the significant AHC of 800 and 1300 S/cm, respectively. The explicit AHC calculation for these alloyed compositions is in good agreement with our predictions. Our findings highlight that chemical alloying is an efficient way to enhance AHC in nodal line hosting materials. © 2024 American Physical Society.