Submit Feedback

Spring 2017

Ramesh Budhani (IIT Kanpur): Quantum Phases and Phase Transitions in Two-Dimentional Highly Correlated Metals at Oxide Interfaces

The two-dimensional diffusive metal stabilized at the interface of SrTiO3 and the Mott Insulator perovskite LaTiO3[1-2] has challenged many notions related to the formation and electronic behavior of the two-dimensional electron gas (2DEG) at the well studies LaAlO3-SrTiO3 interface. Here we discuss specifically the stability of the superconducting phase[3] at LaTiO3 – SrTiO3 interface, the nature of the superconductor – normal metal quantum phase transition (T=0 limit) driven by magnetic field, significance of the field vis-à-vis the Chandrasekhar - Clogston limit for depairing, and how the transition is initiated when the extent of Coulomb interaction amongst charge carriers is modulated by electrostatic gating[4]. The nature of the superconducting condensate is highlighted in the light of the Ti - t2g orbital driven bands and their filling in the presence of a strong Rashba spin – orbit interaction (SOI). Towards the end of the talk, we will discuss the prominent effects of Rashba SOI on normal state quantum transport and how it renormalizes a Kondo-like electronic behavior in range of temperature Tc< T < 5K[5-7]. The prominence of the Ti 3d0 and Ti 3d1 correlated electron physics in these systems will be demonstrated further from our recent studies of 2DEG in ion irradiated SrTiO3 crystals[8,9].
1. Advanced Materials 22, 4448(2010). 2. Phys. Rev. B 86, 075127(2012).
3. Nature Communications, 1, 89(2010). 4. Nature Materials 12, 542(2013).
5. Phys. Rev. B (Rapid Communication) 90, 081107(2014). 6. Phys. Rev. B 90, 075133(2014). 7. Phys. Rev. B 94, 115165 (2016).
8. Phys. Rev. B 91, 205117(2015). 9. Phys. Rev. B 92, 235115 (2015).

Xiaoxing Xi (Temple): Cracking the Nanophysics of Oxide Interface and Heterostructures with Atomic Layer-by-Layer Laser MBE

Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show that atomic layer-by-layer laser molecular-beam epitaxy (ALL-Laser MBE) significantly advances the state of the art in constructing oxide materials with atomic layer precision. Using Sr1+xTi1-xO3 as example, we demonstrate the effectiveness of the technique in producing oxide films with stoichiometric and crystalline perfection. With the growth of La5Ni4O13, a Ruddlesden-Popper phase with n = 4 that has never been reported in the literature, we demonstrate that ALL-Laser MBE allows us to push the equilibrium thermodynamic boundary further. By growing LaAl1+yO3 films of different stoichiometry on TiO2-terminated SrTiO3 substrate at high oxygen pressure, we show that the behavior of the two-dimensional electron gas at the LaAlO3/SrTiO3interface can be quantitatively explained by the electronic reconstruction mechanism. In LaNiO3 films on LaAlOsubstrate with LaAlObuffer layer, we observed the metal insulator transition in 1.5 unit cells, which is driven by oxygen vacancies in addition to epitaxial strain and reduced dimensionality.

United States of America v. Xiaoxing Xi: Why it Matters

As Interim Chair of Temple University’s Physics Department, May 20, 2015 was a normal day for me filled with work on my class, research, promotion of colleagues, and a university task force I was chairing. I had given a public lecture for “Pint of Science,” a science festival, at an Irish pub before picking up my wife at the airport, who was returning from an overseas conference trip. My elder daughter had come home a day earlier from college for a few days. We made a plan to visit a restaurant to try their famous Korean fried chicken. All of this was suddenly and forever changed a few hours later when I was awoken by the urgent pounding on my door. I was arrested by armed FBI agents and indicted by the U.S. government for sharing protected U.S. company technology with China. The indictment was dismissed in September after it had become clear that I did not share the protected technology with China. My case has raised serious concerns about international collaborations in science and technology, civil rights, and the long-term national security and economic future of the United States.

Room Temperature Magnetic Skyrmions in Engineered Multilayer Films

Speaker(s): 
Geoffrey Beach
Dates: 
Friday, April 14, 2017 - 11:30am to 12:30pm

Magnetic skyrmions [1] are particle-like twists of the magnetization taking the form of nanoscale vortices or bubbles that are topologically protected from being continuously ‘unwound’. Their small size, high stability, and ease of manipulation by electric current make them strong candidates for use as information carriers in spintronic memory and logic devices. However, magnetic skyrmions have until recently been restricted to just a few materials and observed only at low temperatures, limiting the experimental accessibility and technological application of these unique...

Cracking the Nanophysics of Oxide Interface and Heterostructures with ALL-Laser MBE

Speaker(s): 
Xiaoxing Xi
Dates: 
Tuesday, April 18, 2017 - 1:00pm to 2:00pm

Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show that atomic layer-by-layer laser molecular-beam epitaxy (ALL-Laser MBE) significantly advances the state of the art in constructing oxide materials with atomic layer precision. Using Sr1+xTi1-xO3 as example, we demonstrate the effectiveness of the technique in producing oxide...

United States of America vs. Xiaoxing Xi: Why It Matters

Speaker(s): 
Xiaoxing Xi
Dates: 
Monday, April 17, 2017 - 4:30pm to 5:30pm

As Interim Chair of Temple University’s Physics Department, May 20, 2015 was a normal day for me filled with work on my class, research, promotion of colleagues, and a university task force I was chairing. I had given a public lecture for “Pint of Science,” a science festival, at an Irish pub before picking up my wife at the airport, who was returning from an overseas conference trip. My elder daughter had come home a day earlier from college for a few days. We made a plan to visit a restaurant to try their famous Korean fried chicken. All of this was suddenly and...

Quantum Behaviors of Graphene Plasmons

Speaker(s): 
Changgan Zeng
Dates: 
Thursday, March 23, 2017 - 4:30pm to 5:30pm

Discovering exotic quantum effects of plasmons and their coupling with other quasiparticles in solids may help to understand such collective excitations at the fundamental level, and further offer quantum-mechanical solution to design future quantum devices with optimized functionalities. In this talk, I will present our recent progress on the quantum behaviors of pasmons in graphene. In particular, I will show the control of plasmon excitation and propagation by tuning the quantum transmission at Heaviside potential steps. Moreover, I will also demonstrate that when the...

Quantum Phases and Phase Transitions in Two-Dimensional Highly Correlated Metals at Oxide Interfaces

Speaker(s): 
Ramesh Budhani
Dates: 
Thursday, April 20, 2017 - 4:00pm to 5:00pm

The two-dimensional diffusive metal stabilized at the interface of SrTiO3 and the Mott Insulator perovskite LaTiO3[1-2] has challenged many notions related to the formation and electronic behavior of the two-dimensional electron gas (2DEG) at the well studies LaAlO3-SrTiO3 interface. Here we discuss specifically the stability of the superconducting phase[3] at LaTiO3 – SrTiO3 interface, the nature of the superconductor – normal metal quantum phase transition (T=0 limit) driven by magnetic field, significance of the field vis-à-vis the Chandrasekhar - Clogston limit for...

My Adventures in Nano-Land

Speaker(s): 
Matthew Johnson
Dates: 
Thursday, March 30, 2017 - 4:30pm to 5:30pm

In this talk, I will describe my background and my approach to the fabrication of nanostructures through three different interdisciplinary projects while highlighting potential applications of the nanosystems we have developed and exciting recent developments in nano-characterization. The first project uses conventional nanoprocessing to fabricate interband cascade lasers. These efficient mid-IR lasers have potential chemical sensing applications and devices of this type have been the preferred mid-IR laser for extra-terrestrial use as methane and water sensors on Mars....

Structure-Activity Relations in Heterogeneous Catalysis – A View from Computational Chemistry

Speaker(s): 
Phillipe Sautet
Dates: 
Friday, March 17, 2017 - 9:30am to 10:30am

The understanding of the catalytic properties of nanoparticle catalysts and the design of optimal composition and structures demands fast methods for the calculation of adsorption energies. By exploring the adsorption of O and OR (R=OH, OOH, OCH3) adsorbates on a large range of surface sites with 9 transition metals, we propose new structure sensitive scaling relations between the adsorption energy of two adsorbates that are valid for all metals and for all surface sites.1 This opens the way for a new class of activity volcano plots where the descriptor is not an energy...

Pages