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Magnetic fluctuations and specific heat in NaxCoO2 near a Lifshitz transition

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journal contribution
posted on 24.07.2015, 09:58 by Sergey Slizovskiy, Andrey Chubukov, Joseph BetourasJoseph Betouras
We analyze the temperature and doping dependence of the specific heat C(T) in Na x CoO 2 . This material was conjectured to undergo a Lifshitz-type topological transition at x=x c =0.62 , in which a new electron Fermi pocket emerges at the Γ point, in addition to the existing hole pocket with large k F . The data show that near x=x c , the temperature dependence of C(T)/T at low T gets stronger as x approaches x c from below and then reverses the trend and changes sign at x≥x c . We argue that this behavior can be quantitatively explained within the spin-fluctuation theory. We show that magnetic fluctuations are enhanced near x c at momenta around k F , and their dynamics changes between x≤x c and x>x c , when the new pocket forms. We demonstrate that this explains the temperature dependence of C(T)/T . We show that at larger x (x>0.65 ) the system enters a magnetic quantum critical regime where C(T)/T roughly scales as logT . This behavior extends to progressively lower T as x increases towards a magnetic instability at x≈0.75 .

Funding

This work was supported by the EPSRC Grants No. EP/H049797/1 and No. EP/l02669X/1, by the Leverhulme Trust and by the U.S. Department of Energy Grant No. DE-FG02-ER46900.

History

School

  • Science

Department

  • Physics

Published in

PHYSICAL REVIEW LETTERS

Volume

114

Issue

6

Pages

? - ? (5)

Citation

SLIZOVSKIY, S., CHUBUKOV, A. and BETOURAS, J.J., 2015. Magnetic fluctuations and specific heat in NaxCoO2 near a Lifshitz transition. Physical Review Letters, 114, 066403

Publisher

© American Physical Society

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2015

Notes

This article was published in the journal, Physical Review Letters [© American Physical Society]. It is also available at: http://dx.doi.org/10.1103/PhysRevLett.114.066403.

ISSN

0031-9007

Language

en

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