Institute for Quantum Materials and Technologies (IQMT)

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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

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

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)

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)

Elastoresistivity in the incommensurate charge density wave phase of BaNi2(As1-xPx)2

The anisotropic strain-dependent electrical transport in BaNi2(As1-xPx)2 (0 ≤ x ≤ 0.10) is not attributed to the coupling of electronic nematicity to the lattice as in the case of the iron-based superconductors, but to uniaxial behaviour of the incommensurate charge density wave (I-CDW) phase.

npj Quantum Mater. 7 (2022) 115

A. Haghighirad is again in 2022 "Highly Cited Researcher"

Just as in the two previous years, A.-A. Haghighirad belongs, together with five other KIT scientists, again in 2022 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 2011 and December 2021.

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

Wolfgang Wernsdorfer member of Académie des sciences

Wolfgang Wernsdorfer was admitted to the french Académie des sciences as one of 16 foreign scientists elected in 2021.

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

Investigation of the Redox Processes in Li-Battery Material

LiaNixMnyCozO2 (a ≈ 1 ; x + y + z ≈ 1), a mixed Li-Mn-Ni-Co oxides ("NMC") like it is used nowadays as battery material in the majority of e-bikes and electric cars, has been investigated with respect to the charging state of the different ions in the various battery charge states over a large number of charging cycles.

Chem. Mater. (2021)

Signatures of a Quantum Griffiths Phase in FeSe0.89S0.11

Signatures of a quantum Griffiths phase have been detected in FeSe1-xSx with x = 0.11 which is caused by the disordered local distribution of Se and S atoms.

Phys. Rev. Lett. 127 (2021) 246402

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

Doping dependence of nematic fluctuations in FeSe1-xSx

The nematic fluctuations in FeSe1-xSx single crystals were investigated as a function of the sulfur content x across the nematic quantum critical point (QCP) xc ≈ 0.17 via Raman scattering.

npj Quantum Mater. 6 (2021) 37

Marginal Fermi liquid behavior of SrIrO3

In a Raman scattering study of SrIrO3 the dynamics of holes and electrons was found to be well described by a marginal Fermi liquid phenomenology with frequency dependent scattering rates close to the Planckian limit.

Nat. Commun. 11 (2020) 4270

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

Nematic quantum phase transition separates superconducting phases in FeSe0.89S0.11

In FeSe0.89S0.11 an evolution of the Fermi surface as a function of applied pressure at the nematic quantum phase transition reveals a Lifshitz transition that separates two distinct superconducting regions.

Nat. Phys. (2019) 41567

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

Uniaxial Pressure Control of Competing Orders in YBa2Cu3O6.67

By high-resolution inelastic x-ray scattering in the high-temperature superconductor YBa2Cu3O6.67 a three-dimensional long-range-ordered Charge Density Wave (CDW) state along the a-axis has been observed under uniaxial stress in the absence of a large magnetic field.

Science 362 (2018) 1040

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

Superconducting pairing analysis via inelastic STM

Tunneling spectra of LiFeAs as direct probe of electronic and bosonic excitations via scanning tunneling microscopy (STM) strongly evidence a nonconventional pairing mechanism, likely via magnetic excitations.

Phys. Rev. Lett. 118 (2017) 167001

Entropy evolution in the magnetic phases of CePdAl

The observed enhanced entropy of CePdAl on application of a magnetic field is explained by the suppression of the Kondo screening of the Ce moments.

Phys. Rev. Lett. 118 (2017) 107204

Switching of a large anomalous Hall effect

The extraordinarily large anomalous Hall effect of antiferromagnetic Mn5Si3 single crystals exhibits strongly anisotropic and features multiple transitions with sign changes at different magnetic fields due to field-induced rearrangements of the magnetic structure despite only tiny variations of the total magnetization.

Sci. Rep. 7 (2017) 42982