Anomalous negative longitudinal magnetoresistance and violation of Ohm's law deep in the topological insulating regime in Bi$$_{1-x}$$Sb$$_x$$

Media type: E-Article
Title: Anomalous negative longitudinal magnetoresistance and violation of Ohm's law deep in the topological insulating regime in Bi$$_{1-x}$$Sb$$_x$$
Contributor: Vashist, Amit; Gopal, R. K.; Singh, Yogesh
imprint: Springer Science and Business Media LLC, 2021
Published in: Scientific Reports
Language: English
DOI: 10.1038/s41598-021-87780-0
ISSN: 2045-2322
Keywords: Multidisciplinary
Origination:
Footnote:
Description: <jats:title>Abstract</jats:title><jats:p>Bi<jats:inline-formula><jats:alternatives><jats:tex-math>$$_{1-x}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow /> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>-</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula>Sb<jats:inline-formula><jats:alternatives><jats:tex-math>$$_x$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow /> <mml:mi>x</mml:mi> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula> is a topological insulator (TI) for <jats:inline-formula><jats:alternatives><jats:tex-math>$$x \approx 0.03$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>≈</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>–0.20. Close to the Topological phase transition at <jats:inline-formula><jats:alternatives><jats:tex-math>$$x = 0.03$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, a magnetic field induced Weyl semi-metal (WSM) state is stabilized due to the splitting of the Dirac cone into two Weyl cones of opposite chirality. A signature of the Weyl state is the observation of a Chiral anomaly [negative longitudinal magnetoresistance (LMR)] and a violation of the Ohm’s law (non-linear <jats:inline-formula><jats:alternatives><jats:tex-math>$$I{-}V$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>I</mml:mi> <mml:mo>-</mml:mo> <mml:mi>V</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>). We report the unexpected discovery of Chiral anomaly-like features in the whole range (<jats:inline-formula><jats:alternatives><jats:tex-math>$$x = 0.032, 0.072, 0.16$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.032</mml:mn> <mml:mo>,</mml:mo> <mml:mn>0.072</mml:mn> <mml:mo>,</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>) of the TI state. This points to a field induced WSM state in an extended <jats:italic>x</jats:italic> range and not just near the topological transition at <jats:inline-formula><jats:alternatives><jats:tex-math>$$x = 0.03$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>. Surprisingly, the strongest Weyl phase is found at <jats:inline-formula><jats:alternatives><jats:tex-math>$$x = 0.16$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> with a non-saturating negative LMR much larger than observed for <jats:inline-formula><jats:alternatives><jats:tex-math>$$x = 0.03$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>. The negative LMR vanishes rapidly with increasing angle between <jats:italic>B</jats:italic> and <jats:italic>I</jats:italic>. Additionally, non-linear <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic> is found for <jats:inline-formula><jats:alternatives><jats:tex-math>$$x = 0.16$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> indicating a violation of Ohm’s law. This unexpected observation of a strong Weyl state in the whole TI regime in Bi<jats:inline-formula><jats:alternatives><jats:tex-math>$$_{1-x}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow /> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>-</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula>Sb<jats:inline-formula><jats:alternatives><jats:tex-math>$$_x$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow /> <mml:mi>x</mml:mi> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula> points to a gap in our understanding of the detailed crystal and electronic structure evolution in this alloy system.</jats:p>
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