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Thermoelectric effects in structures of the quantum Hall effect and the quantum spin Hall

TKM Institutsseminar


Liliana Arrachea


02.08.2019 14:00


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


Universidad Nacional de San Martín (UNSAM), Buenos Aires, Argentina


Prof. Dr. Jörg Schmalian


Boosting the efficiency for the conversion of electrical and thermal energy at finite power is motivating an intense research activity, not only in the areas of material science and applied physics but also in experimental and theoretical areas of statistical mechanics and condensed matter physics. Efforts are concentrated in developing new materials and devices as well as on analyzing different operational conditions. In the latter direction, taking advantage of the quantum effects is one of the most interesting avenues. Nanostructured devices operating at low temperatures are particularly appealing quantum devices, since they offer the conditions for coherent transport, where “parasitic” heat currents by phonons are strongly suppressed.
A two-dimensional electron gas in the quantum Hall regime is one of the most paradigmatic examples of quantum coherent transport. In the first part of the talk, I will present recent results on the thermoelectric response of a quantum dot embedded in a constriction of a quantum Hall bar with fractional filling factors ν = 1/m within Laughlin series. The “figure of merit” ZT for the maximum efficiency at a fixed temperature difference and the thermopower show a significant enhancement in the fractional filling in relation to the integer-filling case, which is a direct consequence of the fractionalization of the electron in the fractional quantum Hall states. [1]
In the second part of the talk I will present results on the thermoelectric response of devices containing pairs of helical edge states of the quantum spin Hall effect. We consider two configurations: (i) the helical pair is connected to an external reservoir with different chemical potential and temperature through a side quantum dot, [2] (ii) the two states of the couple are connected through magnetic islands [3]. In both cases, we discuss the different operational modes and performance.
Finally, I will briefly comment on recent experimental and theoretical results of thermoelectricity in Corbino structures of the quantum Hall effect. [4]

[1] Pablo Roura-Bas, Liliana Arrachea and Eduardo Fradkin, Phys Rev. B (RC) 97, 081104 (2018)
[2] Pablo Roura-Bas, Liliana Arrachea and Eduardo Fradkin, Phys Rev.B 98, 195429 (2018)
[3] Daniel Gresta, Mariano Real, Liliana Arrachea, arXiv:1904.12688
[4] Mariano Real, Daniel Gresta, Christian Reichl, Alejandra Tonina, Paula Giudici, Jürgen Weiss, Werner Wegscheider, Liliana Arrachea and Werner Diestche, in preparation.