Search for new phases of matter using synthetic van der Waals heterostructures

1. Design and fabrication of innovative charge-tunable devices based on atomically-thin layers of transition metal dichalcogenides, graphene, hexagonal boron-nitride etc.

2. Developing opto-electronic techniques for sensing strongly correlated electronic phases (such as Wigner crystals, fractional quantum Hall states, correlated Mott insulators etc.)  in those devices

3. Exploiting high magnetic fields (up to 16 T), ultra-low temperatures (down to 10 mK) and ultra-high vacuum to access electronic correlations.

Optical control of the spin of an individual magnetic dopant in a quantum dot

1. Optimizing performance of spin memories based on single magnetic dopants embedded in molecular-beam-epitaxy-grown  semiconductor quantum dots by:

- prolonging the information storage time in such systems by engineering the quantum dot material, 

- tailoring the ground state of a magnetic dopant with strain,

- implementing novel optical techniques for orienting the dopant spin.

2. Exploring spin dynamics or the effects of exchange interaction between the spin of magnetic ion and that of electrons/holes.

Research Highlights

Direct optical signature of the electronic

 Wigner crystal

If the strength of interactions between the electrons in 2D semiconductor exceeds their kinetic energy, the electrons form a spatially-ordered, Wigner crystal state. Here we provide a direct evidence for the emergence of this elusive state of matter using a novel optical technique that relies on the observation of exciton umklapp scattering in the periodic potential generated by the electrons forming the crystal.

T. Smoleński et al.,  Nature 595, 53-57 (2021)

Evidence for unusual electronic magnetism in an extended 2D system

In typical metals or ferromagnets, collective electronic magnetism arises due to the exchange interaction, which allows the electrons to lower their Coulomb repulsion by aligning their spins. Here we provide a direct experimental evidence for a different, Nagaoka ferromagnetism that occurs due to minimization of kinetic energy of itinerant electrons.

L. Ciorciaro*, T. Smoleński* et al.,
Nature 623, 509-513 (2023)

Optical sensing of fractional quantum Hall effect in optically-inaccessible materials

Despite its great electronic properties, graphene is very hard to access by optical means. Here we utillize Rydberg excitons in a proximal transition metal dichalcogenide monolayer to optically sense the formation of fractional quantum Hall effect in graphene with a sensitivity comparable to state-of-the-art transport methods.

A. Popert, (...), and T. Smoleński .,  Nano Letters 22, 7363-7369 (2022)

Fully-tunable electrostatic confinement of excitons in one and zero dimensions

Although spatial motion of excitons can be confined in self-assembled quantum dots or strain-induced defects, such an approach does not provide in-situ tunability. Here we realize all-electrostatic, fully-tunable confinement of excitons in 1D and 0D by creating later p-i-n junctions in monolayer of transition metal dichalcogenide.

D. Thureja*, E. Yazici*, T. Smoleński* et al.,
arXiv:2402.19278 (2024)

D. Thureja, A. Imamoglu, T. Smoleński et al.,
Nature 606, 238-304 (2022)

Magnetic ground state of an individual Fe2+ ion in strained semiconductor nanostructure

The iron Fe2+ atom embedded in a semiconductor exhibits a single non-degenerate ground state of zero magnetic moment. Here we show that by using sufficiently large strain it is possible to tailor the energy spectrum of the iron atom to obtain doubly degenerate (magnetic) ground state, which can be utilized for storage and processing of the quantum information.

T. Smoleński et al.,  Nat. Commun. 7, 10484 (2016)