arXiv subjects

Dariusz Kaczorowski

Publications and source records attributed to Dariusz Kaczorowski.

At least 73 records · Page 4Linked to original sources

arXiv2019

Extreme Ultraviolet Time- and Angle-Resolved Photoemission Spectroscopy with 21.5 meV Resolution using High-Order Harmonic Generation from a Turn-Key Yb:KGW Amplifier

Characterizing and controlling electronic properties of quantum materials require direct measurements of non-equilibrium electronic band structures over large regions of momentum space. Here, we demonstrate an experimental apparatus for time- and angle-resolved photoemission spectroscopy using high-order harmonic probe pulses generated by a robust, moderately high power (20 W) Yb:KGW amplifier with tunable repetition rate between 50 and 150 kHz. By driving high-order harmonic generation (HHG) with the second harmonic of the fundamental 1025 nm laser pulses, we show that single-harmonic probe pulses at 21.8 eV photon energy can be effectively isolated without the use of a monochromator. The on-target photon flux can reach 5 x 10^10 photons/second at 50 kHz, and the time resolution is measured to be 320 fs. The relatively long pulse duration of the Yb-driven HHG source allows us to reach an excellent energy resolution of 21.5 meV, which is achieved by suppressing the space-charge broadening using a low photon flux of 1.5 x 10^8 photons/second at a higher repetition rate of 150 kHz. The capabilities of the setup are demonstrated through measurements in the topological semimetal ZrSiS and the topological insulator Sb2-xGdxTe3.

physics.ins-det↗

arXiv2019

Observation of topological surface state in a superconducting material

The discovery of topological insulator phase has ignited massive research interests in novel quantum materials. Topological insulators with superconductivity further invigorate the importance of materials providing the platform to study the interplay between these two unique states. However, the candidates of such materials are rare. Here, we report a systematic angle-resolved photoemission spectroscopy (ARPES) study of a superconducting material CaBi2 [Tc = 2 K], corroborated by the first principles calculations. Our study reveals the presence of Dirac cones with a topological protection in this system. Systematic topological analysis based on symmetry indicator shows the presence of weak topological indices in this material. Furthermore, our transport measurements show the presence of large magnetoresistance in this compound. Our results indicate that CaBi2 could potentially provide a material platform to study the interplay between superconductivity and topology.

cond-mat.mes-hall↗

arXiv2019

Temperature Dependent Electronic Structure in a Higher Order Topological Insulator Candidate EuIn$_2$As$_2$

The higher order topological insulator (HOTI) has enticed enormous research interests owing to its novelty in supporting gapless states along the hinges of the crystal. Despite several theoretical predictions, enough experimental confirmation of HOTI state in crystalline solids is still lacking. It has been well known that interplay between topology and magnetism can give rise to various magnetic topological states including HOTI and Axion insulator states. Here using the high-resolution angle-resolved photoemission spectroscopy (ARPES) combined with the first-principles calculations, we report a systematic study on the electronic band topology across the magnetic phase transition in EuIn2As2 which possesses an antiferromagnetic ground state below 16 K. Antiferromagnetic EuIn2As2 has been predicted to host both the Axion insulator and HOTI phase. Our experimental results show the clear signature of the evolution of the topological state across the magnetic transition. Our study thus especially suited to understand the interaction of higher order topology with magnetism in materials.

cond-mat.mes-hall↗

arXiv2019

Magnetic field driven quantum criticality in antiferromagnetic CePtIn4

Physics of quantum critical point is one of the most perplexing topics in current condensed-matter physics. Its conclusive understanding is forestalled by the scarcity of experimental systems displaying novel aspects of quantum criticality. We present a comprehensive experimental evidence of a magnetic field tuned tricritical point separating paramagnetic, antiferromagnetic and metamagnetic phases in novel compound CePtIn$_4$. Analyzing field variations of its magnetic susceptibility, magnetoresistance and specific heat at very low temperatures, we trace modifications of antiferromagnetic structure of the compound. Upon applying magnetic field of increasing strength, the system undergoes metamagnetic transitions which persist down to the lowest temperature investigated, exhibiting first-order-like boundaries separating magnetic phases. This yields a unique phase diagram where the second-order phase transition line terminates at a tricritical point followed by two first-order lines reaching quantum critical end points as $T\to$~0. Our findings demonstrate that CePtIn$_4$ provides innovative perspective for studies of quantum criticality.

cond-mat.str-el↗

arXiv2019

Study on CePtIn4 grown in a platelet-like morphology

We present the results of our comprehensive structural investigation performed on single crystals of CePtIn4 grown from In flux in a platelet-like morphology. They were found to crystalize in an orthorhombic structure having space group Cmcm (no. 63) with the lattice parameters a = 4.52175 (15) Å, b = 16.7777 (5) Å, and c = 7.3903 (2) Å. The unit cell volume of such crystals is slightly larger than that of previously reported needle-shaped single crystals of CePtIn4. This feature seems to influence the low-temperature physical properties of the compound, such as enhanced ordering temperature (TN = 2.3 K versus 1.65 K, observed before) along with a sharp drop in the electrical resistivity at TN (that was absent for the needle-like CePtIn4). In addition to the experimental data, we present the results of our ab-initio calculations of the electronic structure of CePtIn4 with the platelet-like morphology.

cond-mat.str-el↗

arXiv2019

Dirac state switching in transition metal diarsenides

Topological Dirac and Weyl semimetals, which support low-energy quasiparticles in condensed matter physics, are currently attracting intense interest due to exotic physical properties such as large magnetoresistance and high carrier mobilities. Transition metal diarsenides such as MoAs2 and WAs2 have been reported to harbor very high magnetoresistance suggesting the possible existence of a topological quantum state, although this conclusion remains dubious. Here, based on systematic angle-resolved photoemission spectroscopy (ARPES) measurements and parallel first-principles calculations, we investigate the electronic properties of TAs2 (T = Mo, W). Importantly, clear evidence for switching the single-Dirac cone surface state in MoAs2 with the cleaving plane is observed, whereas a Dirac state is not observed in WAs2 despite its high magnetoresistance. Our study thus reveals the key role of the terminated plane in a low-symmetry system, and provides a new perspective on how termination can drive dramatic changes in electronic structures.

cond-mat.mes-hall↗

arXiv2019

Termination Dependent Topological Surface States in Nodal Loop Semimetal HfP2

Symmetry plays a major role in all disciplines of physics. Within the field of topological materials there is a great interest in understanding how the mechanics of crystalline and internal symmetries protect crossings between the conduction and valence bands. Additionally, exploring this direction can lead to a deeper understanding on the topological properties of crystals hosting a variety of symmetries. For the first time, we report the experimental observation of topological surface states in the nodal loop semimetal HfP2 using angle resolved photoemission spectroscopy (ARPES) which is supported by our first principles calculations. Our study shows termination dependent surface states in this compound. Our experimental data reveal surface states linked to three unique nodal loops confirmed by theoretical calculation to be topologically non-trivial. This work demonstrates that transition metal dipnictides provide a good platform to study non-trivial topological states protected by nonsymmorphic symmetry.

cond-mat.mes-hall↗

arXiv2019

Negative longitudinal magnetoresistance as a sign of a possible chiral magnetic anomaly in the half-Heusler antiferromagnet DyPdBi

Magnetotransport investigation of a half-Heusler antiferromagnet DyPdBi revealed hallmark features of Weyl semimetal: huge negative longitudinal magnetoresistance and planar Hall effect. Both effects have recently been linked to chiral magnetic anomaly - axial charge pumping between Weyl nodes. Magnetoresistance (MR) of single crystals of DyPdBi is very pronounced. In magnetic field longitudinal to electrical current direction it reaches -80% and its relative difference with respect to that measured in transverse field (expressed as anisotropic magnetoresistance) is extremely strong: -60% at 10K and 14 T. The planar Hall effect in DyPdBi depends on temperature and magnetic field in non-monotonous way, which has not been previously reported. We compare magnetoresistance measured with voltage contacts on mid-line of the sample with that measured with contacts on its edge, and show that the role of current-jetting, an extrinsic source of anisotropic negative magnetoresistance, is marginal. We discuss that nature of the compound and sample quality exclude intrinsic sources of negative and anisotropic magnetoresistance other than weak localization and the chiral magnetic anomaly.

cond-mat.mtrl-sci↗

arXiv2019

Anisotropic magnetotransport and magnetic phase diagrams of the antiferromagnetic heavy-fermion superconductor Ce$_3$PdIn$_{11}$

We report the results of our detailed magnetotransport studies on single crystals of the antiferromagnetic heavy-fermion superconductor Ce$_3$PdIn$_{11}$. Electrical resistivity measurements, carried out in different magnetic field orientations with respect to the crystallographic axes, were mainly aimed to amass further insight about the magnetically ordered state. The results manifest a clear metamagnetic transitions in the ordered phase when the applied field is parallel to the tetragonal $c$ axis, while no similar features are seen for the transverse direction, i.e., with the field confined within the $ab$ plane. This finding elucidates the fact that the $c$ axis is the easy magnetic direction in this system. Based on the electrical transport and heat capacity data obtained for Ce$_3$PdIn$_{11}$, magnetic field -- temperature phase diagrams were constructed, which elucidate fairly enigmatic behaviors in this material featuring the existence of both second- and first-order magnetic phase transitions.

cond-mat.supr-con↗

arXiv2019

Effect of secondary LuNiSn phase on thermoelectric properties of half-Heusler alloy LuNiSb

We report on the high-temperature (350 K <T< 1000 K) thermoelectric properties of the ternary compounds LuNiSb (cubic) and LuNiSn (orthorhombic) and a composite material (LuNiSb)$_{0.5}$(LuNiSn)$_{0.5}$. The electrical conductivity in LuNiSn is metallic, while it is semiconducting-like in LuNiSb. The Seebeck coefficient reaches -5.5 $μ$V/K at 700 K for the former compound and 66 $μ$V/K at 607 K for the latter one. The composite sample (LuNiSb)$_{0.5}$(LuNiSn)$_{0.5}$ constructed from orthorhombic matrix with cubic inclusions combines the electrical conductivity of LuNiSn with the thermoelectric properties of LuNiSb. Nonetheless, no enhancement of the thermoelectric performance occurs for this material.

cond-mat.mtrl-sci↗

arXiv2019

Ferromagnetic Kondo lattice behavior in Ce11Pd4In9

We report on the low-temperature physical properties of a novel compound Ce$_{11}$Pd$_4$In$_9$ that crystallizes with the orthorhombic Nd$_{11}$Pd$_4$In$_9$-type crystal structure (space group $Cmmm$). The compound exhibits ferromagnetic ordering at $T_{\rm {C}}$ = 18.6 K and an order-order transition at $T_{\rm {t}}$ $\sim$~1.6 K, as inferred from the low-temperature magnetic susceptibility, heat capacity and electrical resistivity data. In the paramagnetic region, the electrical transport in Ce$_{11}$Pd$_4$In$_9$ is dominated by Kondo effect. Below $T_{\rm {C}}$, a distinct contribution due to ferromagnetic spin waves dominates the electrical resistivity data, while at the lowest temperatures, the electrical transport and thermodynamic properties are governed by strong electron-electron correlations. The features observed conjointly hint at strongly correlated ground state in Ce$_{11}$Pd$_4$In$_9$ .

cond-mat.str-el↗

arXiv2019

Magnetic field driven complex phase diagram of antiferromagnetic heavy-fermion superconductor Ce$_3$PtIn$_{11}$

We present the results of our comprehensive investigation on the antiferromagnetic heavy-fermion superconductor Ce$_3$PtIn$_{11}$ carried out by means of electrical transport, heat capacity and ac magnetic susceptibility measurements, performed on single-crystalline specimens down to 50 mK in external magnetic fields up to 9~T. Our experimental results elucidate a complex magnetic field -- temperature phase diagram which contains both first- and second-order field-induced magnetic transitions and highlights the emergence of field stabilized phases. Remarkably, a prominent metamagnetic transition was found to occur at low temperatures and strong magnetic fields. In turn, the results obtained in the superconducting phase of Ce$_3$PtIn$_{11}$ corroborate an unconventional nature of Cooper pairs formed by heavy quasiparticles. The compound is an almost unique example of a heavy fermion system in which superconductivity may coexist microscopically with magnetically ordered state.

cond-mat.supr-con↗

arXiv2018

Observation of topological nodal-loop state in RAs3 (R = Ca, Sr)

Topological nodal-line semimetals (NLSs) are unique materials, which harbor one-dimensional line nodes along with the so-called drumhead surface states arising from nearly dispersionless two dimensional surface bands. However, a direct observation of these drumhead surface states in the currently realized NLSs has remained elusive. Here, by using high-resolution angle-resolved photoemission spectroscopy (ARPES) along with parallel first principles calculations, we examine the topological characteristics of SrAs3 and CaAs3. SrAs3 is found to show the presence of a topological nodal-loop, while CaAs3 is found to lie near a topologically trivial phase. Our analysis reveals that the surface projections of the bulk nodal-points in SrAs3 are connected by drumhead surface states. Notably, the topological states in SrAs3 and CaAs3 are well separated from other irrelevant bands in the vicinity of the Fermi level. These compounds thus provide a hydrogen-like simple platform for developing an in-depth understanding of the quantum phase transitions of NLSs.

cond-mat.mes-hall↗

arXiv2018

Magnetoresistance in YBi and LuBi semimetals due to nearly perfect carrier compensation

Monobismuthides of yttrium and lutetium are shown as new representatives of materials which exhibit extreme magnetoresistance and magnetic-field-induced resistivity plateau. At low temperatures and in magnetic field of 9T the magnetoresistance attains the order of magnitude of 10,000% and 1,000%, on YBi and LuBi, respectively. Our thorough examination of electron transport properties of both compounds show that observed features are the consequence of nearly perfect carrier compensation rather than of possible nontrivial topology of electronic states. The field-induced plateau of electrical resistivity can be explained with Kohler scaling. Anisotropic multi-band model of electronic transport describes very well the magnetic field dependence of electrical resistivity and Hall resistivity. Data obtained from the Shubnikov-de Haas oscillations analysis also confirm that Fermi surface of each compound contains almost equal amounts of holes and electrons. First-principle calculations of electronic band structure are in a very good agreement with the experimental data.

cond-mat.mtrl-sci↗

arXiv2018

Galvanomagnetic properties of the putative type-II Dirac semimetal PtTe$_2$

Platinum ditelluride has recently been characterized, based on angle-resolved photoemission spectroscopy data and electronic band structure calculations, as a possible representative of type-II Dirac semimetals. Here, we report on the magnetotransport behavior (electrical resistivity, Hall effect) in this compound, investigated on high-quality single-crystalline specimens. The magnetoresistance (MR) of PtTe$_2$ is large (over $3000\%$ at $T=1.8$ K in $B=9$ T) and unsaturated in strong fields in the entire temperature range studied. The MR isotherms obey a Kohler's type scaling with the exponent $m$ = 1.69, different from the case of ideal electron-hole compensation. In applied magnetic fields, the resistivity shows a low-temperature plateau, characteristic of topological semimetals. In strong fields, well-resolved Shubnikov - de Haas (SdH) oscillations with two principle frequencies were found, and their analysis yielded charge mobilities of the order of $10^3\,\rm{cm^2V^{-1}s^{-1}}$ and rather small effective masses of charge carriers, $0.11m_e$ and $0.21m_e$. However, the extracted Berry phases point to trivial character of the electronic bands involved in the SdH oscillations. The Hall effect data corroborated a multi-band character of the electrical conductivity in PtTe$_2$, with moderate charge compensation.

cond-mat.mtrl-sci↗

arXiv2018

Superconductivity in the Superhard Boride WB$_{4.2}$

We show that the superhard boride WB$_{4.2}$ is a superconductor with a T$_c$ of 2.05(5) K. Temperature-dependent magnetic susceptibility, electrical resistivity, and specific heat measurements were used to characterize the superconducting transition. The Sommerfeld constant γ for WB$_{4.2}$ is 2.07(3) mJ mol$^{-1}$ K$^{-2}$ and the ΔC/γT$_c$ = 1.56, which is somewhat higher than what is expected for weakly coupled BCS type superconductors. The H$_{c2}$ vs T plot is linear over a wide temperature range but does show signs of flattening by the lowest temperatures studied and therefore the zero-temperature upper critical field (μ$_0$H$_{c2}$(0)) for WB$_{4.2}$ lies somewhere between the linear extrapolation of μ$_0$H$_{c2}$(T) to 0 K and expectations based on the WHH model.

cond-mat.supr-con↗

arXiv2018

High-temperature thermoelectric properties of half-Heusler phases Er$_{1-x}$Ho$_x$NiSb

Polycrystalline samples of Er$_{1-x}$Ho$_x$NiSb ($x$ = 0, 0.2, 0.3, 0.5, 0.7, 0.8, 1) were characterized by means of x-ray powder diffraction (XRD), scanning electron microscopy (SEM), and optical metallography. The results proved the formation of half-Heusler alloys in the entire composition range. Their electrical transport properties (resistivity, thermoelectric power) were studied in the temperature interval 350-1000 K. The measured electrical resistivity spanned between 5 and 25 $μΩ$m. The maximum thermopower of 50-65 $μ$V/K was observed at temperatures 500-650 K. Replacing Ho for Er resulted in a non-monotonous variation of the thermoelectric power factor ($PF = S^2/ρ$). The largest $PF$ of 4.6 $μ$WcmK$^{-2}$ was found at 660 K for Er$_{0.5}$Ho$_{0.5}$NiSb. This value is distinctly larger than PF determined for the terminal phases ErNiSb and HoNiSb.

cond-mat.mtrl-sci↗

arXiv2018

Thermoelectric performance of p-type half-Heusler alloys ScMSb (M = Ni, Pd, Pt) by ab initio calculations

Structural, electronic, and transport properties of ScNiSb, ScPdSb, and ScPtSb were investigated from first principles. Electronic band structures derived within the fully relativistic MBJLDA approach were compared with those obtained from the standard GGA calculations. All the compounds studied exhibit indirect narrow band gaps (0.24-0.63 eV). The effective masses of hole-like carriers are relatively small (0.27-0.36), and decrease with an increasing atomic number of the transition metal component. The carrier relaxation time, required for realistic calculations of the electrical conductivity, was approximated within the deformation potential theory. The GGA approach yielded overestimated transport characteristics with respect to those derived within the MBJLDA analysis. The largest power factor of 4-6 mWK^-2m^-1 ) at high temperatures was obtained for ScPtSb. This value is comparable with those observed experimentally for Fe-Nb-Sb half-Heusler alloys, and hence makes ScPtSb a very good candidate material for thermoelectric applications.

cond-mat.mtrl-sci↗