# Seminar on Condensed Matter Theory

Group of Theoretical Physics at the Department of Condensed Matter Physics

of Charles University has a pleasure to invite you to attend the seminar

on 25th April 2024 at 13:00

at Faculty of Mathematics and Physics of Charles University, Ke Karlovu 5, 121 16 Praha 2

Seminar room **F 052**

### Dr. Emma Minarelli

#### Chalmers University of Technology

## Quantum transport in interacting systems (II): application to semiconductor triple quantum dot, single-molecule benzene transistor and graphene charge-Kondo quantum dot

# Dr. Emma Minarelli » Quantum transport in interacting systems (II): application to semiconductor triple quantum dot, single-molecule benzene transistor and graphene charge-Kondo quantum dot

*Chalmers University of Technology*

This is the second of two lectures on the topic of quantum transport in interacting systems by Dr. Emma Minarelli. The first lecture will be focused on the theoretical foundations and the second on applications. The first lecture will take place on

Tuesday 23. 4. at Na Slovance, the second then onThursday 25. 4. at Ke Karlovu 5.

Location: Seminar room F 052, Ke Karlovu 5

The fabrication of electronic devices on nanometer scale has reached unprecedent control, allowing both for a vast range of industrial applications and access to exotic quantum effects. Among the observables potentially extracted from these devices, electrical conductance holds a primary role due to its direct link between experiments and theoretical models.

In this talk we focus on the Kondo effect, whose experimental verification [1] in semiconductor quantum dot devices is an enhancement of conductance below a characteristic energy scale, the so-called Kondo temperature.

Detailed mesoscopic quantum transport predictions pave the way for a deeper understanding of many-body quantum effects. In the first part of this talk, we presented alternative and improved mesoscopic transport formulae and conductance predictions through generalized effective models. This set of methodologies [2,3] allows to explore system configuration and parameter ranges where standard methods fail.

In this second part of the talk, we show some applications of our methods to relevant systems.

We start with the semiconductor triple quantum dot [2,3], where we characterize its phases in the ac-regime and with applied external magnetic field. We continue with transport through the benzene molecule [4] in a break junction as an electronic switch with a back gate voltage actuator. We investigate this model in two set-up geometries with different symmetries, finding distinct phases. We conclude with a theoretical proposal of a device to study Kondo physics in graphene by means of a two-channel charge-Kondo paradigm [5]. Here, the phases of the system are also given in terms of fixed-point Hamiltonians and visualize in a 3D RG-flow diagram.

[1] D. Goldhaber-Gordon et al. Kondo effect in a single-electron transistor. Nature 1998.

S Sasaki et al. Kondo effect in an integer-spin quantum dot. Nature 2000

[2] E. Minarelli PhD thesis 2022, Quantum transport in interacting nanodevices: from quantum dots to single-molecule transistors

[3] E. Minarelli et al., Linear response quantum transport through interacting multi-orbital nanostructure, arXiv:2209.01208

[4] E. Minarelli et al., forthcoming

[5] E. Minarelli et al. Two-Channel Charge-Kondo Physics in Graphene Quantum Dots Nanomaterials 2022, 12(9), 1513; https://doi.org/10.3390/nano12091513