C. Heß

Leibniz Institute for Solid State and Materials Research

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B. Büchner

Leibniz Institute for Solid State and Materials Research

208

S. Wurmehl

Leibniz Institute for Solid State and Materials Research

R. Klingeler

Heidelberg University

A. U. B. Wolter

Leibniz Institute for Solid State and Materials Research

Bernd Buechner

Leibniz Institute for Solid State and Materials Research

Saicharan Aswartham

Leibniz Institute for Solid State and Materials Research

Federico Caglieris

Superconducting and other Innovative Materials and Devices Institute

G. Behr

Leibniz Institute for Solid State and Materials Research

A. Kondrat

Leibniz Institute for Solid State and Materials Research

Danny Baumann

Leibniz Institute for Solid State and Materials Research

Cooperative Institutions

Leibniz Institute for Solid State and Materials Research

294

TU Dresden

153

Leibniz Association

Centre National de la Recherche Scientifique

Max Planck Institute for Chemical Physics of Solids

Max Planck Society

Leibniz Institute for Neurobiology

University of Cologne

Complexity and Topology in Quantum Matter

Paul Scherrer Institute

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Crystal Growth, Structure, and Transport Properties of the Charge-Transfer Salt Picene/2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane

Crystal Growth & Design (2014)

Benjamin Mahns Olga Kataeva Daut R. Islamov Silke Hampel Frank Steckel

Single crystals of the charge-transfer salt picene/2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane have been grown using physical vapor transport. The crystal structure was determined using single-crystal X-ray diffraction. It was found that the crystals grow in a 1:1 molecular ratio and adopt a monoclinic structure with alternate stacking. Both X-ray data and Raman measurements show that the grown crystals are of good quality. From structure and infrared data, the charge transfer between acceptor and donor molecules was estimated to be approximately 0.14–0.19 electron. Transport measurements indicate a nonmetallic ground state with an activation energy of 0.6 eV. The supporting density functional theory calculations on molecular model systems as well as on crystalline structures confirm the amount of charge transfer and provide first insights into the electronic structure of the new material.

Tetracyanoquinodimethane

Monoclinic crystal system

Acceptor

Crystal (programming language)

10.1021/cg401841n

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Citations (66)

Fermi Arcs Dominating the Electronic Surface Properties of Trigonal PtBi₂

Advanced Physics Research (2024)

Sven Hoffmann Sebastian Schimmel Riccardo Vocaturo Joaquín Puig Grigory Shipunov

Materials combining topologically non-trivial behavior and superconductivity offer a potential route for quantum computation. However, the set of available materials intrinsically realizing these properties are scarce. Recently, surface superconductivity has been reported in PtBi$_2$ in its trigonal phase and an inherent Weyl semimetal phase has been predicted. Here, based on scanning tunneling microscopy experiments, we reveal the signature of topological Fermi arcs in the normal state patterns of the quasiparticle interference. We show that the scattering between Fermi arcs dominates the interference spectra, providing conclusive evidence for the relevance of Weyl fermiology for the surface electronic properties of trigonal PtBi$_2$.

Trigonal crystal system

10.1002/apxr.202400150

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Citations (0)

Photoemission-induced gating of topological insulators

Physical Review B (2011)

A. A. Kordyuk T. K. Kim V. B. Zabolotnyy D. V. Evtushinsky M. Bauch

The recently discovered topological insulators exhibit topologically protected metallic surface states which are interesting from the fundamental point of view and could be useful for various applications if an appropriate electronic gating can be realized. Our photoemission study of Cu intercalated Bi2Se3 shows that the surface states occupancy in this material can be tuned by changing the photon energy and understood as a photoemission induced gating effect. Our finding provides an effective tool to investigate the new physics coming from the topological surface states and suggests the intercalation as a recipe for synthesis of the material suitable for electronic applications.

Topological insulator

Surface States

Inverse photoemission spectroscopy

Photon energy

10.1103/physrevb.83.081303

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Citations (38)

Topological Electronic Structure and Intrinsic Magnetization in MnBi4Te7 : A

Physical Review X (2019)

Raphael C. Vidal Alexander Zeugner Jorge I. Facio Rajyavardhan Ray M. Hossein Haghighi

Combinations of non-trivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances material candidates are emerging. Yet, a compound with a band-inverted electronic structure and an intrinsic net magnetization remains unrealized. MnBi$_2$Te$_4$ is a candidate for the first antiferromagnetic topological insulator and the progenitor of a modular (Bi$_2$Te$_3$)$_n$(MnBi$_2$Te$_4$) series. For $n$ = 1, we confirm a non-stoichiometric composition proximate to MnBi$_4$Te$_7$ and establish an antiferromagnetic state below 13 K followed by a state with net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topological surface state on the MnBi$_4$Te$_7$(0001) surface, analogous to the non-magnetic parent compound Bi$_2$Te$_3$. Our results render MnBi$_4$Te$_7$ as a band-inverted material with an intrinsic net magnetization and a complex magnetic phase diagram providing a versatile platform for the realization of different topological phases.

Topological insulator

10.1103/physrevx.9.041065

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Citations (115)

High-Field Pauli-Limiting Behavior and Strongly Enhanced Upper Critical Magnetic Fields near the Transition Temperature of an Arsenic-DeficientLaO0.9F0.1FeAs1−δSuperconductor

Physical Review Letters (2008)

G. Fuchs S.‐L. Drechsler N. Kozlova G. Behr A. Köhler

We report upper critical field Bc2(T) data for disordered (arsenic-deficient) LaO0.9F0.1FeAs1-delta in a wide temperature and magnetic field range up to 47 T. Because of the large linear slope of Bc2 approximately -5.4 to -6.6 T/K near Tc approximately 28.5 K, the T dependence of the in-plane Bc2(T) shows a flattening near 23 K above 30 T which points to Pauli-limited behavior with Bc2(0) approximately 63-68 T. Our results are discussed in terms of disorder effects within [corrected] unconventional superconducting pairings.

Critical field

Pauli exclusion principle

Flattening

Limiting

10.1103/physrevlett.101.237003

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Citations (88)

Suppressed superconductivity in charge-doped Li(Fe1−xCox)As single crystals

Physical Review B (2011)

Saicharan Aswartham G. Behr Luminita Harnagea Dirk Bombor A. R. Bachmann

Single crystals of the new unconventional superconductor LiFe${}_{1\ensuremath{-}x}$Co${}_{x}$As with $x$$=$ 0, 0.025, 0.05 were grown by a new approach using the self-flux technique. The superconducting transition temperature was found to decrease upon Co doping at the Fe site. Apparently, in LiFeAs this doping scheme suppresses superconductivity, in contrast to the effects of Co doping in other Fe-As compounds, where it suppresses the spin-density wave and establishes superconductivity. Angle-resolved photoemission spectroscopy shows that the bottom of electron-like bands sinks by about 17 meV upon $5%$ Co doping, which indicates that the chemical substitution of Co for Fe in LiFeAs results in charge doping.

10.1103/physrevb.84.054534

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Citations (17)

Phononic-magnetic dichotomy of the thermal Hall effect in the Kitaev-Heisenberg candidate material Na$_2$Co$_2$TeO$_6$

arXiv (Cornell University) (2023)

Matthias Gillig X. C. Hong C. Wellm V. Kataev Weiliang Yao

Majorana fermions as emergent excitations of the Kitaev quantum spin liquid ground state constitute a promising concept in fault tolerant quantum computation. Experimentally, the recently reported topological half-quantized thermal Hall effect in the Kitaev material $\alpha$-RuCl$_3$ seems to confirm the Majorana nature of the material's magnetic excitations. It has been argued, however, that the thermal Hall signal in $\alpha$-RuCl$_3$ rather stems from phonons or topological magnons than from Majorana fermions. Here we investigate the thermal Hall effect of the closely related Kitaev quantum material Na$_2$Co$_2$TeO$_6$, and we show that the thermal Hall signal emerges from at least two components, phonons and magnetic excitations. This dichotomy results from our discovery that the transversal heat conductivity $\kappa_{xy}$ carries clear signatures of the phononic $\kappa_{xx}$, but changes sign upon entering the low-temperature, magnetically ordered phase. We systematically resolve the two components by considering the detailed temperature and field dependence of both $\kappa_{xy}$ and $\kappa_{xx}$. Our results demonstrate that uncovering a genuinely quantized magnetic thermal Hall effect in a Kitaev topological quantum spin liquid requires to disentangle phonon vs. magnetic contributions where the latter include potentially fractionalized excitations such as the expected Majorana fermions.

Thermal Hall effect

Magnon

Majorana fermion

10.48550/arxiv.2303.03067

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Citations (1)

Magnetodielectric and magnetoelastic coupling inTbFe3(BO3)4

Physical Review B (2010)

Umut Adem L. Wang Daniele Fausti W. Schottenhamel P. H. M. van Loosdrecht

We have studied the magnetodielectric and magnetoelastic coupling in TbFe3(BO3)4 single crystals by means of capacitance, magnetostriction and Raman spectroscopy measurements. The data reveal strong magnetic field effects on the dielectric constant and on the macroscopic sample length which are associated to long range magnetic ordering and a field-driven metamagnetic transition. We discuss the coupling of the dielectric, structural, and magnetic order parameters and attribute the origin of the magnetodielectric coupling to phonon mode shifts according to the Lyddane-Sachs-Teller (LST) relation.

Coupling constant

10.1103/physrevb.82.064406

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Citations (60)

Towards ballistic heat transport in the S=1/2 Heisenberg chain compound SrCuO2

arXiv (Cornell University) (2009)

N. Hlubek P. H. Souto Ribeiro R. Saint-Martin A. Revcolevschi Georg Roth

Chain (unit)

Source

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Citations (0)

Phononic-magnetic dichotomy of the thermal Hall effect in the Kitaev material Na2Co2TeO6

Physical Review Research (2023)

Matthias Gillig X. C. Hong C. Wellm V. Kataev Weiliang Yao

The quest for a half-quantized thermal Hall effect of a Kitaev system represents an important tool to probe topological edge currents of emergent Majorana fermions. Pertinent experimental findings for $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ are, however, strongly debated, and it has been argued that the thermal Hall signal stems from phonons or magnons rather than from Majorana fermions. Here, we investigate the thermal Hall effect of the Kitaev candidate material ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}{\mathrm{TeO}}_{6}$, and we show that the measured signal emerges from at least two components, phonons and magnetic excitations. This dichotomy results from our discovery that the longitudinal and transversal heat conductivities share clear phononic signatures, while the transversal signal changes sign upon entering the low-temperature, magnetically ordered phase. Our results demonstrate that uncovering a genuinely quantized magnetic thermal Hall effect in Kitaev topological quantum spin liquids such as $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{RuCl}}_{3}$ and ${\mathrm{Na}}_{2}{\mathrm{Co}}_{2}{\mathrm{TeO}}_{6}$ requires disentangling phonon vs magnetic contributions, including potentially fractionalized excitations such as the expected Majorana fermions.

Magnon

10.1103/physrevresearch.5.043110

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Citations (8)