Howard Yanxon

Status:  Ph.D. Physics, 2nd year

Advisors: Dr. Ravhi Kumar and Dr. Andrew Cornelius

Email: yanxonh@unlv.nevada.edu

Education:

  • B.S. Physics (UNLV, 2015)

Howard Yanxon

Currently, I’m involved in investigating the effect of pressure on the crystal structure, superconducting and charge wave density (CDW) states of TiX (X = S, Se and Te) materials. I believe by studying low-symmetry transition metal dichalcogenide materials under high pressure, a better understanding of the competing states can be achieved. TiX2 is a chalcogenide compound, consisting of alternating close packed titanium and selenium or tellurium layers (X = Se and/or Te). At ambient pressure, TiSe2 compound doesn’t exhibit superconducting state as the temperature approaches 0 K; the superconducting state in this compound is overwhelmed by the CDW. The relationship between superconductivity and the CDW in TiSe2 can be explicitly observed through high pressure and copper intercalation (Figure). The CDW state can be suppressed by applying pressure or copper intercalation. By applying pressure, the superconducting state in TiSe2 compound is observed in the range of 2-4 GPa with diminishing CDW state in which the maximum temperature of 1.8 K observed at 3 GPa [1]. Furthermore, by introducing copper in TiSe2 compound (CuxTiSe2), the superconducting state appears from x= 0.04 going to maximum at x = 0.08 with the temperature of 4 K [2]. More high pressure structural and related experiments are required to understand the origin of superconductivity. I have synthesized the above compounds and characterized them for a systematic HP study. The project is under progress.

Howard Pic 1 Howard Pic 2

Left: Pressure vs. Temperature phase diagram of TiSe2. The superconducting dome is on the range of 2-4 GPa, and Tcmax ≈ 1.8K [1]. Right: CuxTiSe2 phase diagram. Superconducting state appears from x = 0.04 to maximum of Tcmax ≈ 4 K at x = 0.08 [2].

 

References

  1. A.F. Kusmartseva, et al. PRL. 103, 236401 (2009).
  2. E. Morosan, et al. Nature Physics. 2, 544-550 (2006).

Awards and Internships

  •  McNair Summer Internship Fellowship (summer 2015)
  • Russell L. & Brenda Frank Endowed Scholarship (fall 2015)
  • McNair Post-Baccalaureate Scholarship (2016)
  • Summer Internship at Idaho National Laboratory (2017)
  • Donna Weistrop and David B. Shaffer Scholarship (2017 – 2018)

 

Presentations and workshop attended

  •  “Study of Optical Property of CuInTe2 Quantum Dots under Extreme Condition” at the 14th Annual UNLV McNair Scholars Presentation (2015)
  • Attended a Nuclear Resonant Inelastic X-Ray scattering (NRIXS) Workshop at Argonne National Laboratory (2016)
  • “Superconductivity Investigation and Structural Behavior of TiSe2 Compounds under High Pressure” Presentation at the Stewardship Science Academic Programs (SSAP) Symposium (2017)