| Autor: |
Zhang B; Microsystem and Terahertz Research Center, Chengdu 610200, China., Luo Y; Microsystem and Terahertz Research Center, Chengdu 610200, China., Liu Y; Microsystem and Terahertz Research Center, Chengdu 610200, China., Trukhin VN; Ioffe Physical Technical Institute, Polytekhnicheskaya St., 26, St. Petersburg 194021, Russia., Mustafin IA; Ioffe Physical Technical Institute, Polytekhnicheskaya St., 26, St. Petersburg 194021, Russia., Alekseev PA; Ioffe Physical Technical Institute, Polytekhnicheskaya St., 26, St. Petersburg 194021, Russia., Borodin BR; Ioffe Physical Technical Institute, Polytekhnicheskaya St., 26, St. Petersburg 194021, Russia., Eliseev IA; Ioffe Physical Technical Institute, Polytekhnicheskaya St., 26, St. Petersburg 194021, Russia., Alkallas FH; Department of Physics, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia., Ben Gouider Trabelsi A; Department of Physics, College of Science, Princess Nourah bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia., Kusmartseva A; Department of Physics, Loughborough University, Loughborough LE11 3TU, UK., Kusmartsev FV; Microsystem and Terahertz Research Center, Chengdu 610200, China.; Department of Physics, Khalifa University of Science and Technology, Abu Dhabi 127788, United Arab Emirates. |
| Abstrakt: |
We have fabricated α-Sn/Ge quantum well heterostructures by sandwiching nano-films of α-Sn between Ge nanolayers. The samples were grown via e-beam deposition and characterized by Raman spectroscopy, atomic force microscopy, temperature dependence of electrical resistivity and THz time-resolved spectroscopy. We have established the presence of α-Sn phase in the polycrystalline layers together with a high electron mobility μ = 2500 ± 100 cm 2 V -1 s -1 . Here, the temperature behavior of the resistivity in a magnetic field is distinct from the semiconducting films and three-dimensional Dirac semimetals, which is consistent with the presence of linear two-dimensional electronic dispersion arising from the mutually inverted band structure at the α-Sn/Ge interface. As a result, the α-Sn/Ge interfaces of the quantum wells have topologically non-trivial electronic states. From THz time-resolved spectroscopy, we have discovered unusual photocurrent and THz radiation generation. The mechanisms for this process are significantly different from ambipolar diffusion currents that are responsible for THz generation in semiconducting thin films, e.g., Ge. Moreover, the THz generation in α-Sn/Ge quantum wells is almost an order of magnitude greater than that found in Ge. The substantial strength of the THz radiation emission and its polarization dependence may be explained by the photon drag current. The large amplitude of this current is a clear signature of the formation of conducting channels with high electron mobility, which are topologically protected. |
