  Three-dimensionally (3D) frustrated magnets generally exist in the magnetic
diamond and pyrochlore lattices, in which quantum fluctuations suppress
magnetic orders and generate highly entangled ground states (GS). LiYbSe2 in a
previously unreported pyrochlore lattice was discovered from LiCl flux growth.
Distinct from the quantum spin liquid (QSL) candidate NaYbSe2 hosting a perfect
triangular lattice of Yb3+, LiYbSe2 crystallizes in the cubic pyrochlore
structure with space group Fd-3m (No. 227). The Yb3+ ions in LiYbSe2 are
arranged on a network of corner-sharing tetrahedra, which is particularly
susceptible to geometrical frustration. According to our temperature-dependent
magnetic susceptibility measurements, the dominant antiferromagnetic
interaction in LiYbSe2 is expected to appear around 8 K. However, no long-range
magnetic order is detected in thermomagnetic measurements above 70 mK. Specific
heat measurements also show magnetic correlations shifting with applied
magnetic field with a degree of missing entropy that may be related to the
slight mixture of Yb3+ on the Li site. Such magnetic frustration of Yb3+ is
rare in pyrochlore structures. Thus, LiYbSe2 shows promises in intrinsically
realizing disordered quantum states like QSL in pyrochlore structures.
