Papers by Inge Leermakers
Competing quantum phases in Ising superconducting dome of monolayer WS2
Bulletin of the American Physical Society, 2017
The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectac... more The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighboring Weyl points of the same chirality are protected from annihilation by structural distortions or defects, thereby significantly reducing the scattering probability between them. Here we present the electronic properties of the transition metal diphosphides, WP 2 and MoP 2 , which are type-II Weyl semimetals with robust Weyl points by transport, angle resolved photoemission spectroscopy and first principles calculations. Our single crystals of WP 2 display an extremely low residual lowtemperature resistivity of 3 nΩ cm accompanied by an enormous and highly anisotropic magnetoresistance above 200 million % at 63 T and 2.5 K. We observe a large suppression of charge carrier backscattering in WP 2 from transport measurements. These properties are likely a consequence of the novel Weyl fermions expressed in this compound.
Mechanism of the irreversible back gate doping at the LaAlO 3 /SrTiO 3 Interface
Bulletin of the American Physical Society, 2019
Two Dimensional Ising Superconductivity in Gated MoS}$_{\mathrm{\mathbf{2}}}$
Huge magnetoresistance and extremely large conductivity in the type-II Weyl semimetals WP 2 and MoP 2
High field fermiology of the metallized Mott insulator NiS$_2$
Observation of quasi-two-dimensional electron transport in the topological semimetal LaBi
Topological insulators are characterized by the inverted band structure in the bulk and metallic ... more Topological insulators are characterized by the inverted band structure in the bulk and metallic surface states on the surface. In LaBi, a semimetal with a band inversion equivalent to a topological insulator, we observe surface-state-like behavior in the magnetoresistance. The quasi-two-dimensional electrons, however, originate from the bulk states rather topological surface states, which is witness by the angle-dependent quantum oscillations of magnetoresistance and ab-inito calculations. As a consequence, the magnetosresistance exhibits strong anisotropy with large amplitude (~ 10^5 %).
Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO3/SrTiO3 interface
Journal of Physics: Condensed Matter
Physical Review B
The electric-field tunable Rashba spin-orbit coupling at the LaAlO 3 /SrTiO 3 interface shows pot... more The electric-field tunable Rashba spin-orbit coupling at the LaAlO 3 /SrTiO 3 interface shows potential applications in spintronic devices. However, different gate dependence of the coupling strength has been reported in experiments. On the theoretical side, it has been predicted that the largest Rashba effect appears at the crossing point of the d xy and d xz,yz bands. In this work, we study the tunability of the Rashba effect in LaAlO 3 /SrTiO 3 by means of backgating. The Lifshitz transition was crossed multiple times by tuning the gate voltage so that the Fermi energy is tuned to approach or depart from the band crossing. By analyzing the weak antilocalization behavior in the magnetoresistance, we find that the maximum spin-orbit coupling effect occurs when the Fermi energy is near the Lifshitz point. Moreover, we find strong evidence for a single spin winding at the Fermi surface.
Nature Communications
Weyl and Dirac fermions have created much attention in condensed matter physics and materials sci... more Weyl and Dirac fermions have created much attention in condensed matter physics and materials science. Recently, several additional distinct types of fermions have been predicted. Here, we report ultra-high electrical conductivity in MoP at low temperature, which has recently been established as a triple point fermion material. We show that the electrical resistivity is 6 nΩ cm at 2 K with a large mean free path of 11 microns. de Haas-van Alphen oscillations reveal spin splitting of the Fermi surfaces. In contrast to noble metals with similar conductivity and number of carriers, the magnetoresistance in MoP does not saturate up to 9 T at 2 K. Interestingly, the momentum relaxing time of the electrons is found to be more than 15 times larger than the quantum coherence time. This difference between the scattering scales shows that momentum conserving scattering dominates in MoP at low temperatures.
Proceedings of the National Academy of Sciences
Many recent studies show that superconductivity not only exists in atomically thin monolayers but... more Many recent studies show that superconductivity not only exists in atomically thin monolayers but can exhibit enhanced properties such as a higher transition temperature and a stronger critical field. Nevertheless, besides being unstable in air, the weak tunability in these intrinsically metallic monolayers has limited the exploration of monolayer superconductivity, hindering their potential in electronic applications (e.g., superconductor–semiconductor hybrid devices). Here we show that using field effect gating, we can induce superconductivity in monolayer WS2 grown by chemical vapor deposition, a typical ambient-stable semiconducting transition metal dichalcogenide (TMD), and we are able to access a complete set of competing electronic phases over an unprecedented doping range from band insulator, superconductor, to a reentrant insulator at high doping. Throughout the superconducting dome, the Cooper pair spin is pinned by a strong internal spin–orbit interaction, making this mat...
Nature communications, Nov 21, 2017
The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectac... more The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighboring Weyl points of the same chirality are protected from annihilation by structural distortions or defects, thereby significantly reducing the scattering probability between them. Here we present the electronic properties of the transition metal diphosphides, WP2 and MoP2, which are type-II Weyl semimetals with robust Weyl points by transport, angle resolved photoemission spectroscopy and first principles calculations. Our single crystals of WP2 display an extremely low residual low-temperature resistivity of 3 nΩ cm accompanied by an enormous and highly anisotropic magnetoresistance above 200 million % at 63 T and 2.5 K. We observe a large suppression of charge carrier backscattering in WP2 from transport measurements. These properties are likely a cons...
Nature Physics, 2015
The Weyl semimetal (WSM) [1] is a novel gapless state with massless relativistic electrons and pr... more The Weyl semimetal (WSM) [1] is a novel gapless state with massless relativistic electrons and promises exotic transport properties and surface states [2-4] that are different from those of topological insulators (TIs) [5, 6], another famous topological state. Further, normal semimetals (e.g. WTe 2) [7] start a new trend in recent years to realize the large magnetoresistance, the property of a material in which the electrical resistance changes by an external magnetic field. In this Letter, we choose NbP in magneto-transport experiments, because its band structure assembles the WSM [8, 9] and the normal semimetal together. Such a combination in NbP indeed leads to remarkable transport properties observed, an extremely large magnetoresistance of 850,000 % at 1.85 K (250 % at room temperature) in a magnetic field of 9 T without any signs of saturation and an ultrahigh carrier mobility of 5×10 6 cm 2 V −1 s −1 , accompanied by strong Shubnikov-de Hass (SdH) oscillations. NbP presents a fantastic example to design materials funcitonalities by combining the topological and traditional phases.
Physical Review Letters
The interface between the two insulating oxides SrTiO3 and LaAlO3 gives rise to a two-dimensional... more The interface between the two insulating oxides SrTiO3 and LaAlO3 gives rise to a two-dimensional electron system with intriguing transport phenomena, including superconductivity, which are controllable by a gate. Previous measurements on the (001) interface have shown that the superconducting critical temperature, the Hall density, and the frequency of quantum oscillations, vary nonmonotonically and in a correlated fashion with the gate voltage. In this paper we experimentally demonstrate that the (111) interface features a qualitatively distinct behavior, in which the frequency of Shubnikov-de Haas oscillations changes monotonically, while the variation of other properties is nonmonotonic albeit uncorrelated. We develop a theoretical model, incorporating the different symmetries of these interfaces as well as electronic-correlation-induced band competition. We show that the latter dominates at (001), leading to similar nonmonotonicity in all observables, while the former is more important at (111), giving rise to highly curved Fermi contours, and accounting for all its anomalous transport measurements.
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Papers by Inge Leermakers