TY - GEN AU - Kovács-Krausz, Zoltán AU - Nagy, Dániel AU - Márffy, Albin Máté AU - Karpiak, Bogdan AU - Tajkov, Zoltán AU - Oroszlány, László AU - Koltai, János AU - Nemes Incze, Péter AU - Dash, Saroj P AU - Makk, Péter AU - Csonka, Szabolcs AU - Tóvári, Endre TI - Signature of pressure-induced topological phase transition in ZrTe5 PY - 2023 UR - https://m2.mtmt.hu/api/publication/34719870 ID - 34719870 AB - The layered van der Waals material ZrTe5 is known as a candidate topological insulator (TI), however its topological phase and the relation with other properties such as an apparent Dirac semimetallic state is still a subject of debate. We employ a semiclassical multicarrier transport (MCT) model to analyze the magnetotransport of ZrTe5 nanodevices at hydrostatic pressures up to 2 GPa. The temperature dependence of the MCT results between 10 and 300 K is assessed in the context of thermal activation, and we obtain the positions of conduction and valence band edges in the vicinity of the chemical potential. We find evidence of the closing and subsequent re-opening of the band gap with increasing pressure, which is consistent with a phase transition from weak to strong TI. This matches expectations from ab initio band structure calculations, as well as previous observations that CVT-grown ZrTe5 is in a weak TI phase in ambient conditions. LA - English DB - MTMT ER - TY - JOUR AU - Kovács-Krausz, Zoltán AU - Tóvári, Endre AU - Nagy, Dániel AU - Márffy, Albin Máté AU - Karpiak, Bogdan AU - Tajkov, Zoltán AU - Oroszlány, László AU - Koltai, János AU - Nemes Incze, Péter AU - Dash, Saroj P. AU - Makk, Péter AU - Csonka, Szabolcs TI - Revealing the band structure of ZrTe5 using multicarrier transport JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 107 PY - 2023 IS - 7 PG - 10 SN - 2469-9950 DO - 10.1103/PhysRevB.107.075152 UR - https://m2.mtmt.hu/api/publication/33673970 ID - 33673970 LA - English DB - MTMT ER - TY - JOUR AU - Hagymási, Imre AU - Mohd, Isa M.S. AU - Tajkov, Zoltán AU - Márity, K. AU - Oroszlány, László AU - Koltai, János AU - Al-Assaf, Assem Mustafa Abd-Alrhman AU - Kun, Péter AU - Kandrai, Konrád AU - Pálinkás, András AU - Vancsó, Péter AU - Tapasztó, Levente AU - Nemes Incze, Péter TI - Observation of competing, correlated ground states in the flat band of rhombohedral graphite JF - SCIENCE ADVANCES J2 - SCI ADV VL - 8 PY - 2022 IS - 35 PG - 9 SN - 2375-2548 DO - 10.1126/sciadv.abo6879 UR - https://m2.mtmt.hu/api/publication/33090541 ID - 33090541 LA - English DB - MTMT ER - TY - JOUR AU - Tajkov, Zoltán AU - Nagy, Dániel AU - Kandrai, Konrád AU - Koltai, János AU - Oroszlány, László AU - Süle, Péter AU - Horváth, Zsolt Endre AU - Vancsó, Péter AU - Tapasztó, Levente AU - Nemes Incze, Péter TI - Revealing the topological phase diagram of ZrTe5 using the complex strain fields of microbubbles JF - NPJ COMPUTATIONAL MATERIALS J2 - NPJ COMPUT MATER VL - 8 PY - 2022 IS - 1 PG - 7 SN - 2057-3960 DO - 10.1038/s41524-022-00854-z UR - https://m2.mtmt.hu/api/publication/33068873 ID - 33068873 AB - Topological materials host robust properties, unaffected by microscopic perturbations, owing to the global topological properties of the bulk electron system. Materials in which the topological invariant can be changed by easily tuning external parameters are especially sought after. Zirconium pentatelluride (ZrTe5) is one of a few experimentally available materials that reside close to the boundary of a topological phase transition, allowing the switching of its invariant by mechanical strain. Here, we unambiguously identify a topological insulator-metal transition as a function of strain, by a combination of ab initio calculations and direct measurements of the local charge density. Our model quantitatively describes the response to complex strain patterns found in bubbles of few layer ZrTe5 without fitting parameters, reproducing the mechanical deformation-dependent closing of the band gap observed using scanning tunneling microscopy. We calculate the topological phase diagram of ZrTe5 and identify the phase at equilibrium, enabling the design of device architectures, which exploit the topological switching characteristics of the system. LA - English DB - MTMT ER - TY - GEN AU - Koltai, János AU - B., Fecske AU - E., Kósa AU - Oroszlány, László AU - Tajkov, Zoltán TI - A Bell–CHSH-egyenlőtlenségek tesztelése PY - 2021 PG - 8 UR - https://m2.mtmt.hu/api/publication/32522179 ID - 32522179 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Tajkov, Zoltán AU - Koltai, János AU - Cserti, József AU - Oroszlány, László TI - Competition of topological and topologically trivial phases in patterned graphene based heterostructures JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 101 PY - 2020 IS - 23 PG - 8 SN - 2469-9950 DO - 10.1103/PhysRevB.101.235146 UR - https://m2.mtmt.hu/api/publication/31374892 ID - 31374892 N1 - Department of Biological Physics, Elte Eötvös Loránd University, Pázmány Péter sétány 1/A, Budapest, 1117, Hungary Department of Physics of Complex Systems, Elte Eötvös Loránd University, Pázmány Péter sétány 1/A, Budapest, H-1117, Hungary MTA-BME Lendület Topology and Correlation Research Group, Budapest University of Technology and Economics, Budafoki út 8., Budapest, H-1111, Hungary Cited By :3 Export Date: 8 February 2022 Correspondence Address: Tajkov, Z.; Department of Biological Physics, Pázmány Péter sétány 1/A, Hungary; email: novidad21@caesar.elte.hu LA - English DB - MTMT ER - TY - JOUR AU - Tajkov, Zoltán AU - Visontai, David AU - Oroszlány, László AU - Koltai, János TI - Topological Phase Diagram of BiTeX–Graphene Hybrid Structures JF - APPLIED SCIENCES-BASEL J2 - APPL SCI-BASEL VL - 9 PY - 2019 IS - 20 SN - 2076-3417 DO - 10.3390/app9204330 UR - https://m2.mtmt.hu/api/publication/30887683 ID - 30887683 LA - English DB - MTMT ER - TY - JOUR AU - Tajkov, Zoltán AU - Visontai, David AU - Oroszlány, László AU - Koltai, János TI - Uniaxial Strain Induced Topological Phase Transition in Bismuth-Tellurohalide-Graphene Heterostructures JF - NANOSCALE J2 - NANOSCALE VL - 11 PY - 2019 IS - 26 SP - 12704 EP - 12711 PG - 8 SN - 2040-3364 DO - 10.1039/c9nr04519h UR - https://m2.mtmt.hu/api/publication/30636508 ID - 30636508 LA - English DB - MTMT ER - TY - JOUR AU - Rakyta, Péter AU - Alanazy, A. AU - Kormányos, Andor AU - Tajkov, Zoltán AU - Kukucska, Gergő AU - Koltai, János AU - Sangtarash, S. AU - Sadeghi, H. AU - Cserti, József AU - Lambert, C. J. TI - Magic Number Theory of Superconducting Proximity Effects and Wigner Delay Times in Graphene-Like Molecules JF - JOURNAL OF PHYSICAL CHEMISTRY C J2 - J PHYS CHEM C VL - 123 PY - 2019 IS - 11 SP - 6812 EP - 6822 PG - 11 SN - 1932-7447 DO - 10.1021/acs.jpcc.8b11161 UR - https://m2.mtmt.hu/api/publication/30602960 ID - 30602960 N1 - Department of Physics of Complex Systems, ELTE Eötvös Loránd University, Pázmány P. s. 1/A, Budapest, 1117, Hungary Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány P. s. 1/A, Budapest, 1117, Hungary Department of Physics, Lancaster University, Lancaster, LA1 4YB, United Kingdom Department of Mathamatics, Lancaster University, Lancaster, LA1 4YF, United Kingdom Cited By :1 Export Date: 8 February 2022 Correspondence Address: Cserti, J.; Department of Physics, United Kingdom; email: cserti@elte.hu AB - When a single molecule is connected to external electrodes by linker groups, the connectivity of the linkers to the molecular core can be controlled to atomic precision by appropriate chemical synthesis. Recently, the connectivity dependence of the electrical conductance and Seebeck coefficient of single molecules has been investigated both theoretically and experimentally. Here we study the connectivity dependence of the Wigner delay time of single-molecule junctions and the connectivity dependence of superconducting proximity effects, which occur when the external electrodes are replaced by superconductors. Although absolute values of transport properties depend on complex and often uncontrolled details of the coupling between the molecule and electrodes, we demonstrate that ratios of transport properties can be predicted using tables of 'magic numbers,' which capture the connectivity dependence of superconducting proximity effects and Wigner delay times within molecules. These numbers are calculated easily, without the need for large-scale computations. For normal-molecule-superconducting junctions, we find that the electrical conductance is proportional to the fourth power of their magic numbers, whereas for superconducting-molecule-superconducting junctions, the critical current is proportional to the square of their magic numbers. For more conventional normal-molecule-normal junctions, we demonstrate that delay time ratios can be obtained from products of magic number tables. LA - English DB - MTMT ER - TY - JOUR AU - Fülöp, Bálint AU - Tajkov, Zoltán AU - Pető, János AU - Kun, Péter AU - Koltai, János AU - Oroszlány, László AU - Tóvári, Endre AU - Murakawa, H AU - Tokura, Y AU - Bordács, Sándor AU - Tapasztó, Levente AU - Csonka, Szabolcs TI - Exfoliation of single layer BiTeI flakes JF - 2D MATERIALS J2 - 2D MATER VL - 5 ET - 0 PY - 2018 IS - 3 PG - 9 SN - 2053-1583 DO - 10.1088/2053-1583/aac652 UR - https://m2.mtmt.hu/api/publication/3390771 ID - 3390771 N1 - Department of Physics, Budapest University of Technology and Economics, Budafoki út 8, Budapest, 1111, Hungary MTA-BME Condensed Matter Research Group, Budafoki út 8, Budapest, 1111, Hungary Department of Biological Physics, Eötvös Loránd University, Budapest, Hungary Centre for Energy Research, Institute of Technical Physics and Materials Science, 2D Nanoelectronics Lendület Research Group, Budapest, Hungary Department of Physics of Complex Systems, Eötvös Loránd University, Budapest, Hungary MTA-BME Lendület Nanoelectronics Research Group, Budafoki út 8, Budapest, 1111, Hungary Department of Physics, Osaka University, Toyonaka, 560-0043, Japan Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan AB - Spin orbit interaction is strongly enhanced in structures where a heavy element is embedded in an inversion asymmetric crystal field. A simple way for realizing such a setup is to take a single atomic layer of a heavy element and encapsulate it between two atomic layers of different elemental composition. BiTeI is a promising candidate for such a 2D crystal. In its bulk form BiTeI consists of loosely coupled three atom thick layers where a layer of high atomic number Bi are sandwiched between Te and I sheets. Despite considerable recent attention to bulk BiTeI due to its giant Rashba spin splitting, the isolation of a single layer remained elusive. In this work we report the first successful isolation and characterization of a single layer of BiTeI using a novel exfoliation technique on stripped gold. Our scanning probe studies and first principles calculations show that the fabricated 100 mu m sized BiTeI flakes are stable at ambient conditions. Giant Rashba splitting and spin-momentum locking of this new 2D crystal opens the way towards novel spintronic applications and synthetic topological heterostructures. LA - English DB - MTMT ER -