Publications

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Correlation between antiferromagnetic and charge-density-wave order in UPt$_{2}$Si$_{2}$ studied by resonant X-Ray scattering

Fusako Kon, Chihiro Tabata, Kodai Miura, Ruo Hibino, Hiroyuki Hidaka, Tatsuya Yanagisawa, Hironori Nakao, Hiroshi Amitsuka

SciPost Phys. Proc. 11, 011 (2023) · published 5 June 2023 | · pdf

Relationship between antiferromagnetic order with Néel temperature of 35 K and charge-density-wave (CDW) order below 320 K of UPt$_2$Si$_2$ has been investigated by resonant X-ray scattering measurements. We have found that a resonant scattering signal develops below the Néel temperature at the ${ M}_{ 4}$ absorption edge of uranium with a propagation vector of the CDW order ${ q}_{ CDW} \sim$ (0.42, 0, 0). The experimental results reveal that the magnetic structure of UPt$_2$Si$_2$ is modulated by the CDW ordering.

2 citations
Transport and magnetic properties in the Nd diluted system Y$_{1-x}$Nd$_{x}$Co$_{2}$Zn$_{20}$

Rikako Yamamoto, Yasuyuki Shimura, Kazunori Umeo, Toshiro Takabatake, Takahiro Onimaru

SciPost Phys. Proc. 11, 010 (2023) · published 5 June 2023 | · pdf

We report the electrical resistivity, specific heat, and magnetization measurements of Y$_{1-x}$Nd$_{x}$Co$_{2}$Zn$_{20}$ for $0.017 \leq x \leq 0.95$. The Schottky-type specific heat peak at around 13 K for all the samples is reproduced by the crystalline electric field model with the $\Gamma_{6}$ doublet ground state of a Nd$^{3+}$ ion. The magnetization and magnetic susceptibility data of the samples for $x \leq 0.06$ are well reproduced by the calculation without intersite magnetic interactions among Nd moments. Therefore, the dilute Nd system Y$_{1-x}$Nd$_{x}$Co$_{2}$Zn$_{20}$ for $x \leq 0.06$ is a good candidate to study on-site interaction of the $\Gamma_{6}$ doublet ground state of 4$f$ electrons with conduction electrons.

1 citation
Structural and magnetic anisotropy in YBa$_2$Cu$_3$O$_7$/La$_{0.67}$Sr$_{0.33}$MnO$_3$ bilayer on SrTiO$_3$ substrate

Ankita Singh, Ram Prakash Pandeya, Sawani Dutta, Srinivas C. Kandukuri, Kalobaran Maiti

SciPost Phys. Proc. 11, 007 (2023) · published 5 June 2023 | · pdf

We study the magnetic properties and emergence of superconductivity in YBa$_2$Cu$_3$O$_7$ (YBCO)/ La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) heterostructures. Bilayer films of superconducting layer, YBCO, and ferromagnetic layer, LSMO were grown on SrTiO$_{3}$ (STO) (001) substrate using ultrahigh vacuum Pulsed Laser Deposition system. Magnetization data at 100 K as a function of applied magnetic field shows ferromagnetic behaviour due to the LSMO layer. Cooling below 100 K leads to superconductivity in this material; the onset of superconductivity occurs at a temperature, $T_{c,SC},$ of 86 K for $H_{ext}\perp c$ (in-plane) \& 84 K for $H_{ext}||c$ (out-of-plane) under 100 Oe applied field. In-plane magnetic measurements show significant suppression of diamagnetic behaviour as compared to the out-of-plane measurements. The susceptibility signals are higher for out-of-plane direction. Such strong anisotropy in magnetism and the transition temperatures reveal complex interplay of magnetism and superconductivity in this system and calls for further study in this direction.

1 citation
Magnetic properties of the putative higher-order topological insulator EuIn$_2$As$_2$

Tomasz Toliński, Dariusz Kaczorowski

SciPost Phys. Proc. 11, 005 (2023) · published 5 June 2023 | · pdf

In higher-order topological insulator (HOTI), a gap is preserved both for the bulk and the surface states, and only hinges or corners become gapless. Recently, it has been predicted that the antiferromagnetic compound EuIn$_2$As$_2$ can host both the HOTI and axion insulator features. Preliminary experimental confirmation of this finding was obtained using angle-resolved photoemission spectroscopy. The main objective of this work was to characterize the anisotropic magnetic properties of single-crystalline EuIn$_2$As$_2$. In addition, complementary studies on the transport properties, heat capacity, and magnetocaloric effect in this compound were performed.

2 citations
Single crystal growth of PrNiGe$_2$ compounds

Kousei Ishiwatari, Kaito Hoshii, Keisuke Ida, Masashi Ohashi

SciPost Phys. Proc. 11, 002 (2023) · published 5 June 2023 | · pdf

We report on the magnetic characterization of a praseodym intermetallic PrNiGe$_2$. Several single crystals are grown by the Czochralski method from Ni- deficient sample as the initial one. X-ray analysis of PrNi$_{0.8}$Ge$_2$ indicated the CeNiSi$_2$-type structure as the only phase. The magnetic measurements clearly indicate that PrNi$_x$Ge$_2$ exhibits a ferromagnetic orderings at 12 K, which is independent with of composition of Ni. A strong anisotropy along the three principal crystallographic directions was observed, reflecting the orthorhombic symmetry of the crystal structure. The $b$-axis was found to be the easy axis of magnetization.
Revealing the finite-frequency response of a bosonic quantum impurity

Sébastien Léger, Théo Sépulcre, Dorian Fraudet, Olivier Buisson, Cécile Naud, Wiebke Hasch-Guichard, Serge Florens, Izak Snyman, Denis M. Basko, Nicolas Roch

SciPost Phys. 14, 130 (2023) · published 25 May 2023 | · pdf

Quantum impurities are ubiquitous in condensed matter physics and constitute the most stripped-down realization of many-body problems. While measuring their finite-frequency response could give access to key characteristics such as excitations spectra or dynamical properties, this goal has remained elusive despite over two decades of studies in nanoelectronic quantum dots. Conflicting experimental constraints of very strong coupling and large measurement bandwidths must be met simultaneously. We get around this problem using cQED tools, and build a precisely characterized quantum simulator of the boundary sine-Gordon model, a non-trivial bosonic impurity problem. We succeeded to fully map out the finite frequency linear response of this system. Its reactive part evidences a strong renormalisation of the nonlinearity at the boundary in agreement with non-perturbative calculations. Its dissipative part reveals a striking many-body broadening caused by multi-photon conversion. The experimental results are matched quantitatively to a perturbative calculation based on a microscopically calibrated model. Furthermore, we push the device into a regime where perturbative calculations break down, which calls for more advanced theoretical tools to model many-body quantum circuits. We also critically examine the technological limitations of cQED platforms to reach universal scaling laws. This work opens exciting perspectives for the future such as quantifying quantum entanglement in the vicinity of a quantum critical point or accessing the dynamical properties of non-trivial many-body problems.

2 citations
Engineering a pure Dirac regime in ZrTe$_5$

Jorge I. Facio, Elisabetta Nocerino, Ion Cosma Fulga, Rafal Wawrzynczak, Joanna Brown, Genda Gu, Qiang Li, Martin Mansson, Yasmine Sassa, Oleh Ivashko, Martin v. Zimmermann, Felix Mende, Johannes Gooth, Stanislaw Galeski, Jeroen van den Brink, Tobias Meng

SciPost Phys. 14, 066 (2023) · published 11 April 2023 | · pdf

Real-world topological semimetals typically exhibit Dirac and Weyl nodes that coexist with trivial Fermi pockets. This tends to mask the physics of the relativistic quasiparticles. Using the example of ZrTe$_5$, we show that strain provides a powerful tool for in-situ tuning of the band structure such that all trivial pockets are pushed far away from the Fermi energy, but only for a certain range of Van der Waals gaps. Our results naturally reconcile contradicting reports on the presence or absence of additional pockets in ZrTe$_5$, and provide a clear map of where to find a pure three-dimensional Dirac semimetallic phase in the structural parameter space of the material.

2 citations
Sensitivity of a collisional single-atom spin probe

Jens Nettersheim, Quentin Bouton, Daniel Adam, Artur Widera

SciPost Phys. Core 6, 009 (2023) · published 16 February 2023 | · pdf

We study the sensitivity of a collisional single-atom probe for ultracold gases. Inelastic spin-exchange collisions map information about the gas temperature $T$ or external magnetic field $B$ onto the quantum spin-population of single-atom probes, and previous work showed enhanced sensitivity for short-time nonequilibrium spin dynamics [Phys. Rev. X 10, 011018 (2020)]. Here, we numerically investigate the steady-state sensitivity of such single-atom probes to various observables. We find that the probe shows distinct sensitivity maxima in the ($B,T$) parameter diagram, although the underlying spin-exchange rates scale monotonically with temperature and magnetic field. In parameter space, the probe generally has the largest sensitivity when sensing the energy ratio between thermal energy and Zeeman energy in an externally applied magnetic field, while the sensitivity to the absolute energy, i.e., the sum of kinetic and Zeeman energy, is low. We identify the parameters yielding sensitivity maxima for a given absolute energy, which we can relate to a direct comparison of the thermal Maxwell-Boltzmann distribution with the Zeeman-energy splitting. We compare our equilibrium results to nonequilibrium experimental results from a single-atom quantum probe, showing that the sensitivity maxima in parameter space qualitatively prevail also in the nonequilibrium dynamics, while a quantitative difference remains. Our work thereby offers a microscopic explanation for the properties and performance of this single-atom quantum probe, connecting thermodynamic properties to microscopic interaction mechanisms. Our results pave the way for optimization of quantum-probe applications in ($B,T$) parameter space beyond the previously shown boost by nonequilibrium dynamics.

1 citation
Spin and Orbital Spectroscopy in the Absence of Coulomb Blockade in Lead Telluride Nanowire Quantum Dots

M. Gomanko, E. J. de Jong, Y. Jiang, S. G. Schellingerhout, E. P. A. M. Bakkers, S. M. Frolov

SciPost Phys. 13, 089 (2022) · published 10 October 2022 | · pdf

We investigate quantum dots in semiconductor PbTe nanowire devices. Due to the accessibility of ambipolar transport in PbTe, quantum dots can be occupied both with electrons and holes. Owing to a very large dielectric constant in PbTe of order 1000, we do not observe Coulomb blockade which typically obfuscates the orbital and spin spectra. We extract large and highly anisotropic effective Lande g-factors, in the range 20-44. The absence of Coulomb blockade allows direct readout, at zero source-drain bias, of spin-orbit hybridization energies of up to 600 microelectronvolt. These spin properties make PbTe nanowires, the recently synthesized members of group IV-VI materials family, attractive as a materials platform for quantum technology, such as spin and topological qubits.

3 citations
From classical to quantum regime of topological surface states via defect engineering

Maryam Salehi, Xiong Yao, Seongshik Oh

SciPost Phys. Lect. Notes 58 (2022) · published 21 July 2022 | · pdf

Since the notion of topological insulator (TI) was envisioned in late 2000s, topology has become a new paradigm in condensed matter physics. Realization of topology as a generic property of materials has led to numerous predictions of topological effects. Although most of the classical topological effects, directly resulting from the presence of the spin-momentum-locked topological surface states (TSS), were experimentally confirmed soon after the theoretical prediction of TIs, many topological quantum effects remained elusive for a long while. It turns out that native defects, particularly interfacial defects, have been the main culprit behind this impasse. Even after quantum regime is achieved for the bulk states, TSS still tends to remain in the classical regime due to high density of interfacial defects, which frequently donate mobile carriers due to the very nature of the topologically-protected surface states. However, with several defect engineering schemes that suppress these effects, a series of topological quantum effects have emerged including quantum anomalous Hall effect, quantum Hall effect, quantized Faraday/Kerr rotations, topological quantum phase transitions, axion insulating state, zeroth-Landau level state, etc. Here, we review how these defect engineering schemes have allowed topological surface states to pull out of the murky classical regime and reveal their elusive quantum signatures, over the past decade.

1 citation

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