Kai Philippi

Max Planck Institute for Solid State Research

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

H. Takagi

The University of Tokyo

Stefano Checchia

European Synchrotron Radiation Facility

Hsiang‐Hsi Kung

Rutgers, The State University of New Jersey

Samikshya Sahu

University of British Columbia

Konstantin Skokov

Technical University of Darmstadt

Niclas Heinsdorf

University of British Columbia

Andreas P. Schnyder

Max Planck Institute for Solid State Research

Xingxing Xiao

Technical University of Darmstadt

Mohamed Oudah

University of British Columbia

Armin Schulz

Max Planck Institute for Solid State Research

Cooperative Institutions

University of British Columbia

Technical University of Darmstadt

Max Planck Institute for Solid State Research

University of Stuttgart

Stuttgart Observatory

Max Planck Society

TRIUMF

Paderborn University

TU Dresden

Instituto de Ciencia de Materiales de Sevilla

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Anomalous thermal conductivity of alkaline-earth-metal-substituted EuTiO3 induced by resonant scattering

Materials Today Physics (2023)

Xingxing Xiao Wenjie Xie Kai Philippi Yamei Liu Konstantin Skokov

Orthorhombic crystal system

Phonon scattering

Atmospheric temperature range

Lattice (music)

Alkaline earth metal

Anomalous scattering

10.1016/j.mtphys.2023.101132

Cite

Citations (1)

CSD 1984445: Experimental Crystal Structure Determination

The Cambridge Structural Database (2020)

Jürgen Nuß Ulrich Wedig Kai Philippi H. Takagi

10.25505/fiz.icsd.cc24lzc3

Cite

Citations (0)

Discovery of superconductivity and electron-phonon drag in the non-centrosymmetric Weyl semimetal LaRhGe3

npj Quantum Materials (2024)

Mohamed Oudah Hsiang‐Hsi Kung Samikshya Sahu Niclas Heinsdorf Armin Schulz

We present an exploration of the effect of electron-phonon coupling and broken inversion symmetry on the electronic and thermal properties of the semimetal LaRhGe3. Our transport measurements reveal evidence for electron-hole compensation at low temperatures, resulting in a large magnetoresistance of 3000% at 1.8 K and 14 T. The carrier concentration is on the order of 1021/cm3 with high carrier mobilities of 2000 cm2/Vs. When coupled to our theoretical demonstration of symmetry-protected almost movable Weyl nodal lines, we conclude that LaRhGe3 supports a Weyl semimetallic state. We discover superconductivity in this compound with a Tc of 0.39(1) K and Bc(0) of 2.2(1) mT, with evidence from specific heat and transverse-field muon spin relaxation. We find an exponential dependence in the normal state electrical resistivity below ~50 K, while Seebeck coefficient and thermal conductivity measurements each reveal a prominent peak at low temperatures, indicative of strong electron-phonon interactions. To this end, we examine the temperature-dependent Raman spectra of LaRhGe3 and find that the lifetime of the lowest energy A1 phonon is dominated by phonon-electron scattering instead of anharmonic decay. We conclude that LaRhGe3 has strong electron-phonon coupling in the normal state, while the superconductivity emerges from weak electron-phonon coupling. These results open up the investigation of electron-phonon interactions in the normal state of superconducting non-centrosymmetric Weyl semimetals.

Weyl semimetal

Phonon drag

10.1038/s41535-024-00686-8

Cite

Citations (1)

Discovery of Superconductivity and Electron-Phonon Drag in the Non-Centrosymmetric Semimetal LaRhGe$_3$

arXiv (Cornell University) (2023)

Mohamed Oudah Hsiang‐Hsi Kung Samikshya Sahu Niclas Heinsdorf Armin Schulz

We present a comprehensive study of the non-centrosymmetric semimetal LaRhGe$_3$. Our transport measurements reveal evidence for electron-hole compensation at low temperatures, resulting in a large magnetoresistance of 3000% at 1.8 K and 14 T. The carrier concentration is on the order of $10^{21}\rm{/cm}^3$, higher than typical semimetals. We predict theoretically the existence of $\textit{almost movable}$ Weyl nodal lines that are protected by the tetragonal space group. We discover superconductivity for the first time in this compound with a $T_{\text c}$ of 0.39(1) K and $B_{\rm{c}}(0)$ of 2.1(1) mT, with evidence from specific heat and transverse-field muon spin relaxation ($\mu \rm{SR}$). LaRhGe$_3$ is a weakly-coupled type-I superconductor, and we find no evidence for time-reversal symmetry breaking in our zero-field $\mu \rm{SR}$. We study the electrical transport in the normal state and find an unusual $\sim T^{3}$ dependence at low temperature while Seebeck coefficient and thermal conductivity measurements reveal a peak in the same temperature range. We conclude that the transport properties of LaRhGe$_3$ in its normal state are strongly influenced by electron-phonon interactions. Furthermore, we examine the temperature dependent Raman spectra of LaRhGe$_3$ and find that the lifetime of the lowest energy $A_1$ phonon is dominated by phonon-electron scattering instead of anharmonic decay.

Tetragonal crystal system

Muon spin spectroscopy

10.48550/arxiv.2311.11402

Cite

Citations (0)

Modeling and Optimization of Rectangular Latent Heat Storage Elements in an Air-Guided Heat Storage System

Frontiers in Energy Research (2020)

Matti Grabo Christoph Staggenborg Kai Philippi Eugeny Y. Kenig

The thermal performance of macro-encapsulated latent heat storage elements in form of thin, rectangular plates within an air-driven heat storage system is investigated. The plates are made of high-density polyethylene and filled with phase change material. Several plates are stacked together and inserted into a box which can be installed in a heating / air conditioning system. First, an experimental test rig was designed. Measured temperature and pressure drop data retrieved from the rig was then used to validate a simplified computational fluid dynamics model describing a section of the test set-up including a stack of ten plates. Afterwards, the model was further reduced in complexity in order to perform a parametric study by varying geometric parameters of the storage plates. In total, 217 different geometries were simulated and their thermo-hydraulic efficiency was evaluated. As a result, geometries were proposed, which can potentially increase the thermo-hydraulic efficiency of the storage plates by over 50%.

10.3389/fenrg.2020.571787

Cite

Citations (1)

Anomalous Thermal Conductivity of Alkaline-Substituted Eutio3 Induced by Resonant Scattering

Xingxing Xiao Wenjie Xie Kai Philippi Yamei Liu Konstantin Skokov

Thermal conductivities (k) of polycrystalline Eu1–xAxTiO3 (A = Ca, Sr, Ba, 0 ≤ x ≤ 0.8) bulk materials have been measured in the temperature range of ~ 2 K < T < 1173 K. An anomalous double peak feature of k (T) is only observed in the Ca-substituted samples with x ≥ 0.4, which show orthorhombic crystal structure at room temperature (RT). All the other studied samples which display a cubic phase at RT exhibit glass-like k(T) behavior. After excluding the magnetic effects on k and discussing the possible phonon scattering mechanisms in depth, the unusual low-temperature k(T) behavior is related to the delicate lattice structure. In the perovskite-type structure, Eu2+ acts as the root to cause complex disordered local structures and structural instability. The lattice structure of Eu1–xAxTiO3 can be regarded as formed by part-soft part-rigid sublattice. The ultra-low k of Eu1–xAxTiO3 at low temperatures is attributed to resonant scattering, which significantly suppresses thermal transport. The anomalous double peak k(T) structure accounts for a competition between the normal phononic heat transport in the rigid sublattice and the strong damping of heat conduction by resonance scattering in the soft sublattice.

10.2139/ssrn.4384232

Cite

Citations (0)

Numerische Simulation von Gravidestillationsapparaten zur Trennung eines binären Ethanol/Wasser‐Gemisches

Chemie Ingenieur Technik (2020)

Marc Wende Kai Philippi Eugeny Y. Kenig

10.1002/cite.202055148

Cite

Citations (1)

Dependence of the Physical Properties on the Cation Ordering in the New Ternary Phosphide ZnCu ₂ P ₈

Zeitschrift für anorganische und allgemeine Chemie (2020)

Jürgen Nuß Ulrich Wedig Kai Philippi H. Takagi

: The air‐stable phosphide, ZnCu 2 P 8 , was synthesized from its elements in gram amounts. It crystallizes in the Cu 2.5 In 0.5 P 8 structure type [ C 2/ c, Z = 4, a = 1110.8(2) pm, b = 964.7(2) pm, c = 752.7(1) pm, β = 110.027(3)°], and is the first ternary phosphide in the system Zn/Cu/P. Its crystal structure consists of two‐dimensional, layered polyphosphide‐anions, separated by tetrahedrally‐coordinated cations. 135 symmetry independent configurations, each with a different and specific Zn 2+ and Cu + arrangement, where explored with density functional methods. Whereby, each of the 135 cation ordering pattern has a diverse bandgap, and the total energies vary in the range of 1 eV. As several configurations with low energy are close in energy, an intrinsic disorder is discussed as origin of the promising low lattice thermal conductivity, observed.

Phosphide

Lattice (music)

Indium phosphide

10.1002/zaac.202000099

Cite

Citations (4)