Transverse voltage in zero external magnetic fields, its scaling and violation of the time reversal symmetry in MgB2

TL;DR

This study reports the observation of transverse voltage in MgB2 without external magnetic fields, revealing a violation of time-reversal symmetry near the critical temperature and proposing a new scaling relation between resistivities.

Contribution

It presents the first measurement of zero-field transverse voltage in MgB2 and introduces a novel scaling law linking transverse and longitudinal resistivities near T_c.

Findings

Non-zero transverse resistance observed near T_c

Scaling relation $ ho_{xy} o d ho_{xx}/dT$ established

Evidence suggesting violation of time-reversal symmetry

Abstract

The longitudinal and transverse voltages (resistances) have been measured for MgB$_2$ in zero external magnetic fields. Samples were prepared in the form of thin film and patterned into the usual Hall bar shape. In close vicinity of the critical temperature T$_c$ non-zero transverse resistance has been observed. Its dependence on the transport current has been also studied. New scaling between transverse and longitudinal resistivities has been observed in the form $\rho{_{xy}}\sim d\rho{_{xx}}/dT$. Several models for explanation of the observed transverse resistances and breaking of reciprocity theorem are discussed. One of the most promising explanation is based on the idea of time-reversal symmetry violation.