Effects of uniaxial pressure on the spin ice Ho2Ti2O7

Why?

Since the invention of the transistor and the photovoltaic cell, it has been clear that an understanding of emergent electronic and magnetic phenomena is of greatest importance for the development of modern society and sustainability.

The low temperature properties of Ho2Ti2O7 has pusseled scientists for over two decades. The degenerate ground state of this material presents a vacuum for emergent magnetic monopole excitations. This new state of matter is of great interest, as it allows for magnetic charges to flow like electricity, which might be useful in future applications of information technology. The material is also of great interest in the aspect of fundamental research.

How?

Neutron scattering experiments on Ho2Ti2O7 under uniaxial pressure were performed at the Institut Laue-Langevin (ILL), France. When the material is subject to pressure, the electromagnetic interactions change, and this can be observed via neutron scattering. The study can be simulated, and we can understand in detail how the pressure influence interactions. This also allows for us to predict new ground states of materials in this category. The figure shows the three main aspects of our collaboration, (a), theoretical modelling, (b), crystal synthesis, and (c), Neutron scattering.

Figure: (a) Theoretical model. (b) Ho2Ti2O7 crystal synthesised at Lund University (Sweden). (c) Neutron scattering results on Ho2Ti2O7 uniaxial pressure, with comparison to theory.

What´s next?

Now we aim to explore further effects of pressure, develop better measurement techniques and pressure cells. We are also using the neutron scattering data to conduct further theoretical work with hope of finding novel phases of matter in these materials.

Who?

This work resulted from a joint collaboration between researchers at the KTH Royal Institute of Technology (Sweden), European Spallation Source (ESS, Sweden), Copenhagen university (Denmark), Lund University (Sweden), Oslo University (Norway), Åbo Akademi (Finland) and Kyushu Institute of Technology (Japan). The project was supported by Nordforsk through the program NNSP (Project No. 82248) and by the Danish Agency for Research and Innovation through DANSCATT.

Collaborators: R. Edberg (KTH), I. M. B. Bakke (Oslo University), H. Kondo (Kyushu Institute of Technology), L. Ørduk Sandberg (Copenhagen university), M. L. Haubro (Copenhagen university), M. Guthrie (ESS), A. T. Holmes (ESS), J. Engqvist (Lund University), A. Wildes (ILL), K. Matsuhira (Kyushu Institute of Technology), K. Lefmann(Copenhagen university), P. P. Deen (ESS), M. Mito (Kyushu Institute of Technology), and P. Henelius (KTH, Åbo Akademi)

Check out the full article at the American Physical Society, Phys. Rev. B 102, 184408

DOI: 10.1103/PhysRevB.102.184408

Contact:

Richard Edberg, Ph.D student, KTH Royal Institute of Technology

ricedb@kth.se