Hydrodynamics in anisotropic Dirac systems

TKM Institutsseminar

Vortragender:

Julia M. Link

Datum:

27.07.2017 12:30

Ort:

Room 10.01, 10th Floor, Bldg. 30.23, KIT Campus South

Zugehörigkeit:

Karlsruhe Institute of Technology

Gastgeber:

Prof. Dr. Jörg Schmalian

Abstract

In the hydrodynamic regime it is possible to investigate the universal collision-dominated dynamics of the isolated electron fluid, while the couplings to the lattice and to impurities becomes seconadry. This regime has become recently experimentally accessible such as the observance of the break-down of the Wiedemann-Franz law [1,2], negative local resistance [3,4] and a giant magnetodrag [5] in graphene as well as the dependence of the magnetoresistivity on the length of the sample for PdCoO2 [6,7] and (Al,Ga)As heterostructures[8] shows.
Thus far hydrodynamic behavior has been studied in systems with high symmetry of their electronic spectrum, such as Dirac-fluids and Galilei invariant Fermi liquids.
We will study the hydrodynamic behavior in anisotropic Dirac-systesms, i.e. systems where two Dirac cones merge in momentum space [9,10]. These systems have in one direction a parabolic enery dispersion relation while in the perpendicular direction their energy dispersion will be linear. This anisotropy leads to fascinating transort properties. In the same material metallic and insulating behavior can be found depending on the direction of the electrical field. Furthermore we find for the shear viscosity coefficents different temperature functions depending on the flow direction. In fact, the infamous ratio η/s of the viscosity and entropy density diverges and vanishes, depending on the electron-flow direction, violating the lower bound obtained from the duality of strongly coupled field theories and gravity models [11].



References

[1] J. Crossno, J. K. Shi, K. Wang, X. Liu, A. Harzheim, A. Lucas, S. Sachdev, P. Kim, T. Taniguchi, K. Watanabe, T. A. Ohki, and K. C. Fong, Science 351, 1058 (2016).
[2] R. Franz and G. Wiedemann, Annalen der Physik 165, 497 (1853).
[3] D. A. Bandurin, I. Torre, R. Krishna Kumar, M. Ben Shalom, A. Tomadin, A. Principi, G. H. Auton, E. Khestanova1, K. S. Novoselov, I. V. Grigorieva1, L. A. Ponomarenko, A. K. Geim, and M. Polini, Science 351, 1055 (2016).
[4] L. Levitov and G. Falkovich, Nat Phys advance online publication (2016), letter.
[5] M. Titov, R. V. Gorbachev, B. N. Narozhny, T. Tudorovskiy, M. Schütt, P. M. Ostrovsky, I. V. Gornyi, A. D. Mirlin, M. I. Katsnelson, K. S. Novoselov, A. K. Geim, and L. A. Ponomarenko, Phys. Rev. Lett. 111, 166601 (2013).
[6] P. J. W. Moll, P. Kushwaha, N. Nandi, B. Schmidt, and A. P. Mackenzie, Science 351, 1061 (2016).
[7] R. N. Gurzhi, Sov. Phys. JETP 20, 953 (1965).
[8] M. J. M. de Jong and L. W. Molenkamp, Phys. Rev. B 51, 13389 (1995).
[9] Shinya Katayama, Akito Kobayashi, and Yoshikazu Suzumura, Phys. Soc. Jpn. 75 (2006), 054705
[10] A. Kobayashi, Y. Suzumura, F. Piéchon, and G. Montambaux, PRB 84 (2011), 075450
[11] P. K. Kovtun, D. T. Son, and A.O. Starinets, PRL 94 (2005), 111601