Department of Applied Physics

Correlated Quantum Materials (CQM)

Theoretical condensed matter physics, focusing on emergent properties of quantum materials.
CQM image

 

The Correlated Quantum Materials (CQM) group focuses on theoretically studying emerging quantum phenomena in solid-state systems. In particular, we are highly interested in materials where electronic correlations and topology yield exotic physics such as symmetry broken states, topological excitations and ultimately emerging fractionalized particles. A central part of our research focuses on two-dimensional materials, including graphene and two-dimensional magnetic materials. In our group, we aim to provide theoretical routes to engineer exotic states of matter in twisted van der Waals systems, including twisted graphene multilayers. As specific goals, we aim to unveil potential routes to engineer unconventional superconductors, quantum spin liquids, topological states and fractionalized matter in van der Waals materials.  Besides our purely theoretical research line, we often work in collaboration with experimental groups studying quantum materials in general, and two-dimensional materials in particular.

 

Current main research lines:

vdW magnet
Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling, Science 360 (6394), 1218-1222 (2018)

Emergent quantum phenomena in van der Waals materials
Van der Waals heterostructures provide an outstanding platform to engineer elusive quantum phenomena, by exploiting materials engineering, twist engineering and proximity effects. We are interested in developing new theoretical routes to exploit the flexibility of these materials to create exotic physics not accessible in conventional compounds. On the theory side, among others, in this line, we recently showed how to generate artificial gauge fields, tunable frustrated magnets, and controllable correlated states in twisted graphene multilayers. In collaboration with experimental groups, we recently showed how to probe magnetic excitations in van der Waals magnetshow to drive van der Waals magnets to a frustrated regime by spin-orbit engineering, and how to probe crystal field effects in twisted graphene multilayers.

 

Cascade
Critical cascade in quasiperiodic chains, Nature Physics 16, 832–836 (2020)

Interacting & quasiperiodic topology and exotic excitations in condensed matter systems
The interplay of strong electronic interactions and topology represents one of the most exciting lines in condensed matter, opening venues to engineer quantum excitations not present in nature, such as fractionalized excitations, supersymmetric excitations and emergent topological states. Among others, in this line, we recently showed how to create Chern insulators by exploiting interactions in topological metalshow to engineer topological excitations by exploiting quasiperiodic many-body states, how to create solitonic excitations between quantum disordered magnets and superconductors, and in collaboration with an experimental group how to generate and probe critical quasiperiodic states

 

TSC
Two-dimensional topological superconductivity with antiferromagnetic insulators, Phys. Rev. Lett. 121, 037002 (2018)

Engineering and detecting unconventional superconductivity
Unconventional superconductors are highly pursued for their exotic quantum properties, and ultimately for their potential for topological quantum computing. However, these states are extremely rare to find and detect in nature, with very few compounds showing signatures of such physics. Among others, in this line, we recently showed how to create a topological superconductor with antiferromagnets, how to detect the interplay between atomic defects and moire superconductivity in twisted graphene bilayershow to detect non-unitary multiorbital superconductors in angle-resolved photo-emission spectroscopy experiments, and how to probe the non-uniform superfluid density in superconducting twisted graphene trilayers.

frustrated
Controlling magnetism via spin-orbit coupling engineering, Science Advances Vol. 6, no. 30, eabb9379 (2020)

Method development for topological and correlated quantum materials
Understanding exotic phenomena in quantum systems often requires developing new theoretical methods for model analysis and prediction. In particular, we are especially interested in developing new methodologies to understand and detect topological phenomena, and emergent quantum excitations in many-body systems. In this direction, recently we demonstrated how to use machine learning methods to detect topological matter with local measurements, how to disentangle magnetic anisotropy mechanisms from first principles methods, how to compute dynamical topological excitations in many-body systems using kernel polynomial tensor-network methods, and how to probe and quantify intervalley scattering in atomistic models of graphene multilayers. Most of the methods we develop are implemented in freely available open source libraries we have developed to solve quantum many-body problems with tensor networks and study electronic, interacting and topological properties of tight binding models

Current group members:
- Jose Lado: Assistant professor
- Guangze Chen: Doctoral candidate
- Maryam Khosravian: Doctoral candidate (co-supervised with Prof. Peter Liljeroth)
- Rouven Koch: Doctoral candidate
- Pascal Vecsei: Doctoral candidate (co-supervised with Prof. Christian Flindt)
- Timo Hyart: Research Fellow
- Pramod Kumar: Postdoctoral researcher
- Faluke Aikebaier: Postdoctoral researcher (co-supervised with Prof. Tero Heikkilä)

Former group members
- Timo Kist: Research assistant (co-supervised with Prof. Christian Flindt)
Vilja Kaskela: Research assistant
Senna Luntama: Research assistant (co-supervised with Prof. Päivi Törmä)

Research Group Members

 Jose Lado

Jose Lado

Assistant Professor
 Guangze Chen

Guangze Chen

Doctoral Candidate
 Maryam Khosravian

Maryam Khosravian

Doctoral Candidate
 Rouven Koch

Rouven Koch

Doctoral Candidate
 Pascal Vecsei

Pascal Vecsei

Doctoral Candidate
 Timo Hyart

Timo Hyart

Research Fellow
 Pramod Kumar

Pramod Kumar

Postdoctoral researcher
 Faluke Aikebaier

Faluke Aikebaier

Postdoctoral researcher
CQM retreat

From left to right: Guangze Chen, Timo Hyart, Jose Lado, Timo Kist, Maryam Khosravian, Senna Luntama 

Recent Events & News

A cartoon showing a graphene lattice with a strip of blue in the middle representing the topological superconductor

A path to graphene topological qubits

Researchers demonstrate that magnetism and superconductivity can coexist in graphene, opening a pathway towards graphene-based topological qubits

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Department of Applied Physics Research Seminar: Mohamed Oudah

Dr. Mohamed Oudah (UBC, Can) will give a research seminar "Unusual Sn State in the Superconducting Disordered Selenide Ag1-xSn1+xSe2"

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Department of Applied Physics Research Seminar: Maia G. Vergniory

Dr. Maia Garcia Vergniory (Donostia International Physics Center/Ikerbasque, Spain) will give a research seminar "Beyond Topological Quantum Chemistry"

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Twisted graphene sheets give rise to electrons with exotic properties

A magnetic twist to graphene

By combining ferromagnets and two rotated layers of graphene, researchers open up a new platform for strongly interacting states using graphene’s unique quantum degree of freedom

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Profile

AQP Seminar: A NEAT Quantum Error Decoder

Aalto Quantum Physics Seminar (Zoom). Speaker: Prof. Evert van Nieuwenburg (Niels Bohr International Academy, Denmark)

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Department of Applied Physics Research Seminar: Eliška Greplová

Prof. Eliška Greplová (TU-Delft Netherlands) will give a research seminar "Learning Algorithms for Control and Characterization of Quantum Matter".

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Department of Applied Physics Research Seminar: Dr. Timo Hyart

Dr. Timo Hyart (International Research Centre MagTop, Warsaw, Poland) will give a research seminar "Correlated States in Flat-Band Systems".

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Magnetic materials

A road to frustration

Aalto University theorist part of a team that opens up a new route to design exotic frustrated
quantum magnets.

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Scanning tunneling microscope tip confining electrons in graphene

Stopping the unstoppable with atomic bricks

Aalto University theorist part of a team that developed a method for trapping elusive electrons

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Schematic of a wave passing through a quasiperiodic structure

A critical cascade

New Nature Physics paper shows how quantum particles approach an elusive critical regime in a quasiperiodic structure.

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Meet our newest Academy of Finland Fellows

Our researchers who have been awarded Academy of Finland Fellowships tell us about what their projects will investigate

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Atomic scale quantum materials colloquium: new online colloquium series

The colloquium will present novel developments in the field of atomic manipulation with scanning probe techniques and atomically designed quantum matter. This Colloquium series will start on May 4th, and run once a week, preliminary until the end of June.

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Department of Applied Physics Research Seminar: Dr. Aline Ramires

Dr. Aline Ramires (Max Planck Institute for the Physics of Complex Systems, Dresden, Germany) will give a research seminar "Understanding Complex Superconductors through the Concept of Superconducting Fitness".

Events
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Physics Research Seminar

Tobias Wolf (ETH Zürich, Switzerland) will give the seminar "Metamaterials from Twisted Honeycomb Lattices" about his research.
Hosted by Prof. Jose Lado.

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Events
Professor Lado in the physics department coffee room

How to create things that don’t exist

The newest theoretical physics professor at Aalto calculates what we need to do to create electronic states that can’t otherwise exist in nature, and how we can harness them for quantum computing

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