Hidden one-dimensional spin modulation in a three-dimensional metal

Abstract

Pressure can transform a transparent material into an opaque one, quench the moments in a magnet and force solids to flow like liquids. At 15 GPa, the pressure found 500 km below the earth's surface, the semiconductors silicon and germanium superconduct. Yet, at this same pressure, we show here that the magnetism in metallic GdSi remains completely robust even as it shrinks by one-seventh of its volume. Non-resonant X-ray magnetic diffraction in a specially designed diamond anvil cell, combined with band structure calculations, reveal the stability of the incommensurate spin density wave, which can be traced to a persistently nested portion of the Fermi surface that becomes increasingly onedimensional under pressure. A cooperative interaction between nested, itinerant spins and local magnetic moments provides the organizing principle for the modulated magnetic order, salient both for its insights into the role of topology in ordered states and its potential functionality.

Direct probe of Fermi surface evolution across a pressure-induced quantum phase transition

“…The complex response of the Fermi surface to the application of large pressuresfrom changing the electron kinetic energy and thereby affecting the bandwidth of a particular band [27] to inducing charge transfer between bands [28] -is difficult to parse. The combined technique of x-ray magnetic diffraction and Hall measurements provides direct tracking of both the slow charge transfer process between nesting bands and the overall P-T evolution of itinerant charge carriers.…”

“…A major improvement over previous work [34] was to utilize a pair of wide-angle (60 o 2θ) perforated diamond anvils [28] (Fig. 1) to significantly reduce the elastic background.…”

“…Non-resonant magnetic diffraction under pressure was carried out at beam line 4-ID-D of the Advanced Photon Source, using horizontally polarized 20 keV x-rays diffracting in the vertical plane [27,28,34]. A major improvement over previous work [34] was to utilize a pair of wide-angle (60 o 2θ) perforated diamond anvils [28] (Fig.…”

“…The Fermi surfaces of these 2k F systems at ambient pressure are often calculable with ab initio band structure calculations [6,25,26] and directly measureable through techniques such as ARPES [5,6]. The pressure evolution of the incommensurate ordering wave vectors can be measured directly using diffraction techniques [24,27,28] to reflect features on the Fermi surface [7][8][9][10][19][20][21].…”

Sub-Kelvin magnetic and electrical measurements in a diamond anvil cell with in situ tunability

“…2,4,5 High pressure measurements at cryogenic temperatures of 4 K and below have been performed using a wide range of experimental techniques, including electrical transport, [4][5][6][7][8][9][10] magnetic susceptibility, 7,9,11 Shubnikov-de Haas and de Haas-van Alphen quantum oscillations, 12,13 infrared and Raman spectroscopy, 14,15 and neutron and x-ray magnetic diffraction. 10,[16][17][18][19] Pressure-driven experiments at temperatures below 1 K (Refs. 4, 6, 9, and 20) entail the use of cryostats such as recirculating helium-3 (Ref.…”