Research Highlights

Order parameter dynamics of Fermi liquids

Order-parameter fluctuations of metals are a rich research field from the theoretical and experimental points of view. Additionally, nowadays there is an enormous interest in electronic systems with multipolar interactions, one example is the quadrupolar interaction which drives nematic phase transitions in a plethora of compounds [1, 2]. In the following I will discourse about my contribution to this area of research:

We have found an interesting feature in which two real collective modes melt at a point of the excitation spectrum, acquiring an imaginary part. We have identified this feature as an Exceptional Point [3-4] that appears in the weak attractive interaction region for 2D Fermi liquids with dipolar and quadrupolar interaction.

We completely characterize this singularity, explicitly showing its topological properties [4].

We discussed experimental signatures in different set-ups: pump-probe spectroscopy, to observe the dynamic response in the time domain [4]; and in the AC conductivity of Fermi liquids with dipolar and quadrupolar interactions in a narrow slab. We show that the finite size of the slab imprints clear signatures of the collective mode spectrum in the conductivity as well as in the dephasing between the electric field and the current density [5].

[1] E. Fradkin, S. A. Kivelson, M. J. Lawler, J. P. Eisenstein, and A. P. Mackenzie, Annu. Rev. Condens. Matter Phys. 1, 153 (2010).
[2] R. M. Fernandes, A. V. Chubukov, and J. Schmalian, Nat. Phys. 10, 97 (2014).
[3] R. Aquino and D. G. Barci, Phys. Rev. B 100, 115117 (2019).
[4] R. Aquino and D. G. Barci, Phys. Rev. B 102, 201110(R) (2020).
[5] R. Aquino and D. G. Barci, Phys. Rev. B 104, 195150 (2021).

Topological phase transitions of non-hermitian chains

Fluctuations of heat in stochastic systems

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