Institute for Quantum Materials and Technologies (IQMT)


We are looking for qualified candidates with Bachelor, Master oder PhD degree for the realization of our research program.
For inquiries about our topical job offers at IQMT please contact
Prof. Matthieu Le Tacon

Welcome at IQMT

Modern electronics are based on semiconducting materials in which the behavior of electrons can be accurately described using the laws of quantum mechanics derived at the beginning of the 20th century. Many other intriguing aspects of quantum physics, such as quantum coherence, superposition of states or entanglement, open groundbreaking perspectives for a 'second quantum revolution' in the fields of information, communication or computing technologies. These phenomena are delicate to observe in ordinary materials and remain largely unexploited.

Combining experiment and theory, the researchers at the Institute for Quantum Materials and Technologies (IQMT) at KIT seek to understand quantum phenomena in condensed matter and molecular systems, and to develop novel devices based on these effects that will serve as building blocks for future quantum technologies .

 

Publication Highlights / News

Annealing-Tunable Charge Density Wave in the Magnetic Kagome Material FeGe

The formation of a charge density wave (CDW) in the magnetic kagome material FeGe within the antiferromagnetic phase (AFM) can be explained by the disordered formation of dimers of Ge atoms displaced out of the Fe3Ge layers (Ge1a → Ge1b).

Phys. Rev. Lett. 132 (2024) 256501

Giant Two-Level Systems in a Granular Superconductor

An experimental investigation of two-level systems (TLS) in granular aluminum thin films under applied mechanical strain and electric fields revealed a class of strongly coupled TLS having electric dipole moments up to 30 e⁢Å, an order of magnitude larger than dipole moments commonly reported for solid state defects.

Phys. Rev. Lett. 132 (2024) 217002

Understanding the Electrochemical Reaction Mechanism of the Cathode Material Na2/3Mn7/12Fe1/3Ti1/12O2 for Sodium-Ion Batteries

Using Na2/3Mn7/12Fe1/3Ti1/12O2 (NMFTO) as an optimized cathode material for Na-ion batteries, an initial discharge capacity of 170 mA h g–1 at a 0.1 C rate and a capacity retention of 80% after 50 cycles was achieved.

Chem. Mater. 36 (2024) 4107

Colossal c-axis response and lack of rotational symmetry breaking within the Kagome planes of the CsV3Sb5 superconductor

Bulk thermodynamic measurements (high-resolution thermal expansion, heat capacity, elastoresistance) on CsV3Sb5 single crystals reveal a strong competition between the charge-density wave (CDW) and the superconducting states which is dramatically influenced by c-axis tuning where the CDW is characterized by a strongly enhanced A1g-symmetric elastoresistance.

Phys. Rev. Lett. 132 (2024) 186001

Battery research with synchrotron radiation

With the new measuring instrument NAPXAS (Near Ambient Pressure X-ray Absorption Spectroscopy), energy conversion and ageing processes in battery energy storage systems can be investigated spectroscopically under quasi-normal wet chemical conditions during battery operation.

KIT-Presseinformation 39 (2024)

Interplay between 2D and 3D charge density waves in underdoped high-temperature superconducting YBa2Cu3Oy

A hard x-ray diffraction study on underdoped YBa2Cu3Oy under uniaxial stress as external tuning parameter revealed a competition between 2D and 3D charge density wave orders which simultaneously compete with superconductivity.

Nat. Commun. 15 (2024) 3277

Observation of Josephson harmonics in tunnel junctions

Higher-harmonics deviations of the current–phase relations of AlOx tunnel Josephson junctions from the standard sinusoidal form as extracted from experimental energy spectra of various transmon circuits indicate a possible optimization route for superconducting Qubit circuits.

Nat. Phys. (2024)

Full phonon softening above the CDW phase transition in 2H-TaSe2

Inelastic x-ray scattering (IXS) studies with meV resolution on the Charge Density Wave (CDW) transition in 2H-TaSe2 reveal an extended temperature region between T* = 128.7 K and the ordering temperature of the incommensurate CDW phase TCDW = 121.3 K, where the full phonon softening of a longitudinal acoustic phonon mode at qCDW = (0.323,0,0) occurs, i.e. there exists a temperature window where lattice fluctuations, observed as the overdamped soft phonons, coexist with static but only medium-range-sized CDW domains, which form a long-range ordered state only for T ≤ TCDW.

Nat. Commun. 14 (2023) 7282

Nano-assembled open quantum dot nanotube devices

A novel preparation technique for the mechanical integration of carbon nanotubes (CNTs) into electronic circuits enables significantly more transparent CNT-metal interfaces and thus the realisation of superconducting qubits or flux-mediated optomechanics based on carbon nanotubes.

Commun. Mater. 5 (2024) 5

EU Project on Quantum-Limited Microwave Amplifiers

The EU-funded and KIT-coordinated project "TruePA" aims at the further development of a "Truly Resilient Quantum Limited Traveling Wave Parametric Amplifier" , an amplifier device for weak microwave signals which could be a key component for quantum cryptography, communication, or computing.

KIT-News 2023 (0)

Hot luminescence from single-molecule chromophores electrically and mechanically self-decoupled by tripodal scaffolds

Enlarging the π-systems of the footing substituents of the tripodal scaffold molecule enabled the spectrally and spatially resolved observation of the hot luminescence bands of individual self-decoupled chromophores.

Nat. Commun. 14 (2023) 8253

Amir-Abbas Haghighirad is again in 2023 "Highly Cited Researcher"

Just as in the three previous years, Amir-Abbas Haghighirad belongs, together with four other KIT scientists, again in 2023 to the "Highly Cited Researchers" , a ranking list which comprises the names of the scientists with the highest number of citations of their publications between January 2012 and December 2022.

KIT-News (2023)

Giant lattice softening in Sr2RuO4 due to electronic Lifshitz transition

Using a piezo-based uniaxial pressure cell to tune the ultraclean metal Sr2RuO4 while measuring the stress-strain relationship, revealed a huge lattice softening which could be attributed to a Lifshitz transition of a two-dimensional Fermi surface demonstrating that the lattice softening is driven entirely by the conduction electrons of the relevant energy band.

Science 382 (2023) 447

ERC Synergy Grant for Axion Detector based on Superconducting Qubits

The 6-year international project "Quantum Technologies for Axion Dark Matter Search" ("DarkQuantum" for short) has been awarded an ERC Synergy Grant worth €12.9 million, including around €2 million for KIT, to build a system based on superconducting qubits as extremely low-noise detectors for the experimental detection of axions, previously hypothetical elementary particles that are considered promising candidates for dark matter.

KIT-Presseinformation 87 (2023)

Improved primary high pressure scale challenges current understanding of Earth's core physics

By combined measurement of the acoustic velocities and the density from a rhenium sample in a diamond anvil cell using inelastic x-ray scattering and x-ray diffraction a primary pressure scale could be established which extends to the multimegabar pressures of Earth’s core and leads to the conclusion that the present picture of the physics of Earth’s core has to be revised.

Sci. Adv. 9 (2023) 8706

Band-resolved Caroli–de Gennes–Matricon states of multiple-flux-quanta vortices in a multiband superconductor

Using scanning tunneling microscopy, the winding number of individual vortices in Pb in the intermediate state at mK temperature could be determined from the real space wave function of its Caroli–de Gennes–Matricon bound states.

Sci. Adv. 9 (2023) 9163

Giant Non-Volatile Electric Field Control of Proximity Induced Magnetism in SrIrO3

In heterostructures with proximity-induced magnetic SrIrO3, a giant variation of the anomalous Hall conductivity and Hall angle as a function of the applied gate voltage Vg by up to 700% were observed.

Adv. Funct. Mater. (2023) 2308346

Dresden Physics Prize 2023 for Jörg Schmalian

Jörg Schmalian receives the Dresden Physics Prize of the Year 2023 in recognition of his research in the field of condensed matter theory and in recognition of his contributions to promoting close cooperation between the Max Planck Institute for the Physics of Complex Systems (MPI-PKS) and the TU Dresden.

Physik-Preis Dresden (2023)

High-Purity Entanglement Using Nonreciprocity

In a collaboration of FU Berlin, Princeton University, Hebrew University of Jerusalem and KIT it is proposed utilizing nonreciprocity to enhance the robustness of continuous-variable entanglement of propagating modes against thermal fluctuations, achieving high-purity flying entangled states through the breaking of reciprocity in a two-mode squeezing interaction and leveraging pairwise Gaussian interactions, making it well-suited for parametric circuit-QED implementations, e.g. in superconducting circuitry.

PRX QUANTUM 4 (2023) 20344

Co-substituted Magnetic Metal Halide Perovskite

Substitution of Co2+ into the lattice of methylammonium lead triiodide (MA(Pb:Co)I3) was shown to impart magnetic behavior to the material while maintaining photovoltaic performance at low concentrations.

Small Methods (2023) 2300095

Fe(II) Spin Crossover molecules on magnetic Co/Au(111)

For a sub-monolayer of Fe(II) spin crossover (SCO) complex molecules deposited on Au passivated Co films on Au(111) it could be demonstrated that the SCO complexes in the high spin state interact ferromagnetically with the ferromagnetic Co film and stilll maintain their SCO ability.

Small (2023) 2300251

Monitoring the Formation of Li-Battery Cathode Materials

The syntheses of Ni-poor (“NCM111”, LiNi1/3Co1/3Mn1/3O2) and Ni-rich (“NCM811” LiNi0.8Co0.1Mn0.1O2) lithium transition-metal oxides were investigated using in situ synchrotron powder diffraction and near-edge X-ray absorption fine structure spectroscopy.

Chem. Mater. 35 (2023) 1514

STM activation of the electroluminescence of individual molecules on a Au substrate

STM experiments provide evidence that it is possible to activate the electroluminescence of individual 2,6-core-substituted naphthalene diimide molecules directly deposited onto a Au(111) substrate.

Phys. Rev. Lett. 130 (2023) 36201

Soft-Phonon and Charge-Density-Wave Formation in BaNi2As2

Energy-resolved inelastic x-ray scattering investigation of the incommensurate charge density-wave (I-CDW) in BaNi2As2 revealed by direct comparison with ab initio density functional calculations a phonon instability as origin of the transition to the I-CDW state.

Phys. Rev. Lett. 129 (2022) 247602

Granular aluminium nanojunction fluxonium qubit

Nanoscopic Josephson junctions created by a single-layer deposition of a 20 nm thin film of granular aluminium and lithographical definition of 20 nm wide nanobridges showed in a simple qubit circuit similar coherence times in the microsecond range as Al–AlOx–Al superconductor–insulator–superconductor (SIS), the present state-of-the-art Josephson junction for qubit circuits, however with even better technical perspectives for the construction of more complex qubit circuits.

Nat. Mater. (2022)

Localization of electrons in the nematic phase

Magnetotransport studies of thin flakes of FeSe revealed an an unusual asymmetry between the mobilities of the electrons and holes in the nematic electronic phase, with hole-like quasiparticle with a lighter effective mass and a quantum scattering time three times shorter, as compared with bulk FeSe and a localization of the negative charge carriers by reducing the dimensionality.

PNAS 119 (2022) 2200405

Electronic nematic liquid in BaNi2As2

In BaNi2As2 a large splitting of doubly degenerate phonon lines was observed well above symmetry breaking and attributed to a dynamical effect, rooted in a particularly strong coupling between these phonons and fluctuations between degenerate electronic nematic configurations.

Nat. Commun. 13 (2022) 4535

Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects

Single-tube devices based on (7, 5) carbon nanotubes, functionalized with dichlorobenzene molecules, and wired to graphene electrodes showed electrically generated, defect-induced emissions that are controllable by electrostatic gating and strongly red-shifted compared to emissions from pristine nanotubes.

ACS Nano (2022)

Elastocaloric Determination of the Phase Diagram of Sr2RuO4

A piezoelectric-based device was used to map out the phase diagram of Sr2RuO4 by identifying changes of sign of the elastocaloric response function as a function of temperature with phase transitions.

Nature 607 (2022) 276

Fluxons in High-Impedance Long Josephson Junctions

The characteristic impedance of long Josephson junctions could be increased by an order of magnitude using thin films of a high kinetic inductance superconductor as electrodes, which makes these junctions suitable for a variety of applications in superconducting electronics.

Appl. Phys. Lett. 120 (2022) 112601

Molecular Crystals for Quantum Information Devices

Novel molecular crystals containing rare-earth ions exhibit optical linewidths that are 3 to 4 orders of magnitude narrower than those of any previously known molecular system thus enabling their use as spin-photon interfaces for photonic quantum technologies.

Nature 603 (2022) 241

Topological Magnon Band Structure in a Skyrmion Lattice

Inelastic neutron-scattering measurements indicate the formation of Landau levels for magnons in the skyrmion phase of MnSi.

Science 375 (2022) 1025

Proximity-induced Ferromagnetism in SrIrO3

In SrIrO3/LaCoO3 heterostructures ferromagnetism and a strong, intrinsic and positive anomalous Hall effect could be induced in the SrIrO3 layer by proximity to the ferromagnetic insulating LaCo3.

Adv. Mater. 34 (2022)

Momentum Dependence of Electron-Phonon Coupling

Strong renormalization of the life time of lattice vibrations, i.e. phonons, can occur in the absence of both Fermi surface nesting and lattice anharmonicity if electron-phonon coupling is strongly enhanced for specific values of electron-momentum.

Nat. Commun. 13 (2022) 228

Spin-Readout of Single-Molecule Magnet with STM

In Bis(phthalocyaninato)dysprosium (DyPc2) single molecules on Au(111) the Dy moment has been determined by milli-Kelvin scanning tunneling microscopy.

Phys. Rev. Lett. 127 (2021) 123201

Effect of natural radioactivity on superconducting qubits

The effect of natural radioactivity on the operation of superconducting qubit circuits has been investgated in collaboration of KIT and Istituto Nazionale di Fisica Nucleare (INFN).

Nat. Commun. 12 (2021) 2733

Electromigration and Quantum Phase Slip in Al nanowires

Via electromigration the normalconducting resistance RN of Al nanowires could be reduced by up to 3 orders of magnitude to select hereby insulating, metallic or superconducting behaviour which enabled the validation of Quantum Phase Slip ("QPS") behaviour of superconducting nanowires.

ACS Nano 15 (2021) 4108

Disproof of divergent nematic susceptibility in CsFe2As2

By neutralization of thermal expansion in a piezoelectric-based strain cell the strain dependence of the electrical resistivity of CsFe2As2 the electron system response could be shown to be largely symmetric in the Fe2As2 plane.

Phys. Rev. Lett. 125 (2020) 187001

All-optical polarization of the ground-state nuclear spins of Eu-Ions

Long-lived spectral holes have been burnt in the absorption spectrum of a binuclear Eu(III) complex which demonstrate an efficient polarization of the ground-state nuclear spins of the rare-earth ions.

Nat. Commun. 12 (2021) 2152

ELASTO-Q-MAT initiative funded by DFG

A new Transregional Collaborative Research Center (SFB-TRR) in close cooperation between the Karlsruhe Institute of Technology (KIT), the Goethe University Frankfurt, the Johannes Gutenberg University Mainz, the Max Planck Institute of Polymer Research in Mainz, and the Max Planck Institute for Chemical Physics of Solids in Dresden will investigate quantum materials whose properties can be dramatically changed through elastic deformations.

Nematic correlation length in Fe-based superconductors

By inelastic x-ray scattering the nematic correlation length ξ has been extracted from the anomalous softening of acoustic phonon modes in FeSe and Ba(Fe1-xCox)2As2 (x = 0.03, 0.06).

Phys. Rev. Lett. 124 (2020) 157001

Record Magnetic Performance in FePt Nanomaterials

In ferromagnetic FePt nanoparticles, an unprecedented energy product of 80 MGOe at room temperature well above the previous record 59 MGOe in NdFeB has been achieved.

Small (2019) 1902353

Low-Energy Phonon Anomalies in Cuprates with Stripes

A precise measurement of the lattice vibrations in stripe-ordered La2-xBaxCuO4 showed that the fluctuating CDW correlations that exist at high temperature have a different periodicity than the static ordered CDW but the same periodicity as YBa2Cu3O6+δ.

Phys. Rev. X 8 (2018) 11008

Thermodynamic Evidence for FFLO-State in KFe2As2

The magnetic phase diagram of KFe2As2 near the upper critical field provides with a clear double transition when the field is strictly aligned in the FeAs plane and a characteristic upturn of the upper critical field line, which goes far beyond the Pauli limit at 4.8 T firm evidence of a Fulde-Ferrell-Larkin-Ovchinnikov ("FFLO").

Phys. Rev. Lett. 119 (2017) 217002

Dominant magnetic interactions in BaFe2As2

For BaFe2As2 the magnetic susceptibility and resistivity anisotropies measured on application of a large symmetry breaking strain strongly suggest that magnetism plays the dominant role in the hierarchy of interactions based on magnetic as well as to orbital, lattice, and nematic degrees of freedom.

Nat. Commun. 8 (2017) 504

TiOx nanotubes for gas-analytical multisensors

TiOx nanotube layers on multisensor array chips demonstrated at operating temperatures up to 400°C a promising sensitivity and selectivity towards organic vapors in the ppm range.

Sci. Rep. 7 (2017) 9732

Raman scattering from Higgs mode in Ca2RuO4

Raman scattering and neutron scattering provide strong evidence for excitonic magnetism in Ca2RuO4.

Phys. Rev. Lett. 119 (2017) 67201

Electron-phonon coupling in Topological Insulators

The electron-phonon interaction in the metallic surface state of the 3D topological insulators Bi2Se3 and Bi2Te3 is carried by optical modes of polar character which is weakly screened by the metallic surface state.

Sci. Rep. 7 (2017) 1059